Good bye friends

Une monnaie capricieuse

Le matérial dont nous avons besoin pour réaliser l'expérience est:

Un verre
Une monnaie
Une carte d'un jeu de cartes

Préparation

Mets la carte sur le verre et la monnaie au centre de la carte.
Fixe le verre avec une main et tire la carte avec l'autre main avec énergie.
Le monnaie tombe dans le verre.

Qu'est-ce qui s´est passé?

La résistance d´un corps à changer son état de repos ou de mouvement s´appelle inertie.
Après avoir tiré la carte, la force de frottement entre la carte et la monnaie tend à deplacer la monnaie sur la carte. Si nous le faisons avec énergie, la force de frottement ne réussit pas à surpasser l´inertie de la monnaie qui tombe dans le verre. Mais si nous tirons lentement de la carte, la monnaie se déplace sur la carte.

Vous avez compris?

Begoña et Julia

La chaleur de nos mains

Le matériel dont nous avons besoin c´est:

Un pot de verre avec un couvercle
Une paille de rafraîchissement
Colle
Alcool

Nous pouvous faire un trou sur le couvercle avec un marteau et un clou.

Nous mettons la paille dans le trou et nous remplissons d´alcool le pot (plus ou moins deux centimètres). Et nous plaçons le couvercle.

Nous couvrons le pot avec nos mains et nous voyons que l´alcool monte par la paille.

Explication

La température de notre corps est supérieure à la température de l´air dans le pot
Pour entourer le pot avec nos mains fournissons de l´énergie au pot et comme ça augmente la température de l´air dans le pot. Cela produit l´augmentation de la pression aussi qui pousse le liquide que monte par la paille.

Si nous levons le convercle du pot, la pression dans l´interieur récupére sa valeur originale et le liquide qui monte par la paille tombe dans le pot.

Alicia, Marta et Jiamei

Skydiver

A nice work done by 12th year physics' students Nuno Oliveira and Filipa Martins about skydiving and terminal speed.

Rainbow Milk

Group 5 - Elena B, Cynthia C, Karina L, Laura P - Colegiul Naţional "Mihai Eminescu" Satu Mare, România

Red, blue and yellow are called the primary colors. Just by mixing these colors, you can get all the colors of the rainbow:
RED + YELLOW = ORANGE; RED + BLUE = PURPLE; BLUE + YELLOW = GREEN

What you need: red, blue and yellow food color; 1 cup milk; dish soap; shallow bowl

Directions:

• Pour 1 cup of milk into the bowl

• Add 3 drops of red food color to one edge of the bowl

- 1/3 of the way away, add 3 drops of blue food color
- 1/3 of the way away add 3 drops of yellow
- don't mix or jiggle the bowl

• Squeeze a drop of dish soap in the center of the bowl

• Record what you see.

• What do you think happened?

"Shaving foam"

Decomposition of H2O2 :

To carry that experiment you need:

• high buret
• 30% hydrogen peroxide (perhydrol)
• solid potassium or sodium iodide ( KI or NaI)
• soap powder

BE CAREFUL! 30% HYDROGEN PEROXIDE IS VERY CORROSIVE!

Pour perhydrol into the buret (about 1/5 of its height), then pour the soap powder -
about 1 teaspoonful. Mix the soap with the liquid.

After that add 1/2 of teaspoonful of solid potassium iodide. Be carefull because foam appears very quickly and it could make some brown stain - it contains iodine I2 .

3H2O2 + KI = 3H2O + KIO + O2

2KIO + H2O2 = I2 + 2KOH + O2

Oxygen causes a lot of foam if soap is mixed with perhydrol before adding KI.


http://www.youtube.com/watch?v=OKUgIKPPwhE

Concave Mirrors

A movie of experiments using one and two concave mirrors.

Bernoulli principle with balloons

A movie about Bernoulli's principle applied to a stream of air passing between two balloons.

The balloon that doesn't explode

A balloon full of water can be burned for a long while by a burner without exploding.

Barbeque balloon

This is an experiment where we can see that vegetable oil may create a membrane that prevents a balloon from exploding.

Potassium and water

This video is about the reaction of potassium and water.

Air versus Water 2

An experiment that shows that at small depths atmospheric pressure is bigger than water pressure.

Effusive Volcano

An experiment with balsamic vinegar and baking powder to produce an effusive volcano.

Plasma Ball

This is an experiment about plasma. In physics and chemistry, plasma is a partially ionized gas, in which a certain proportion of electrons are free rather than being bound to an atom or molecule. The ability of the positive and negative charges to move somewhat independently makes the plasma electrically conductive so that it responds strongly to electromagnetic fields. Plasma therefore has properties quite unlike those of solids, liquids or gases and is considered to be a distinct state of matter.

Layered Liquids

Group 5 - Elena B, Cynthia C, Karina L, Laura P - Colegiul Naţional "Mihai Eminescu" Satu Mare, România

Have you ever heard the phrase "oil and water don’t mix"? First we will test that expression, then look at interesting combination of several other liquids.

Oil and Water

You will need the following materials:

• ¼ cup (60 ml) water
• ¼ cup (60 ml) vegetable oil
• a small glass
• food coloring

First pour the water into the glass. Add a couple of drops of food coloring and mix. Next add the oil. What do you see? Which layer is on top?

Tightly cover the glass with plastic wrap or your hand (if it's big enough). While holding the glass over a sink (in case you spill), shake the glass so that the two liquids are thoroughly mixed. Set the glass down and watch what happens. Do oil and water mix?

The word “miscibility” describes how well two substances mix. Oil and water are said to be “immiscible,” because they do not mix. The oil layer is on top of the water because of the difference in density of the two liquids. The density of a substance is the ratio of its mass (weight) to its volume. The oil is less dense than the water and so is on top.

The next experiment examines the miscibility and density of several liquids.

You will need the following materials:

• ¼ cup (60 ml) dark corn syrup or honey
• ¼ cup (60 ml) dishwashing liquid
• ¼ cup (60 ml) water
• ¼ cup (60 ml) vegetable oil
• ¼ cup (60 ml) rubbing alcohol
• a tall 12 ounce (350 ml) glass or clear plastic cup
• two other cups for mixing
• food coloring

Take the 12 ounce glass. Being careful not get syrup on the side of the glass; pour the syrup into the middle of the glass. Pour enough syrup in to fill the glass 1/6 of the way.

After you have added the syrup or honey, tip the glass slightly and pour an equal amount of the dishwashing liquid slowly down the side of the glass. Does the dishwasher liquid float on top of the syrup or sink to the bottom?

Next mix a few drops of food coloring with water in one of the mixing cups. Color the rubbing alcohol a different color in another mixing cup.

Be careful to add the next liquids VERY SLOWLY. They are less viscous (i.e., not as thick) and mix more easily than the previous liquids. We don't want them to mix. Tip the glass slightly, and pouring slowly down the side of the glass, add first the colored water, then the vegetable oil, and finally the colored rubbing alcohol.

On a piece of paper, make a sketch of the glass and its liquids, labeling the position of each liquid in your glass.

Why do the liquids stay separated? Can you think of several ways that the liquids in the glass are different? Try to describe some properties that differ in each of the liquids in the glass.

One property that is different in all of the liquids is color. Another property unique to each liquid is thickness (viscosity).

The property of the liquids that is responsible for the layering effect is density. Can you guess what the relationship is between the density of a liquid and its position in the glass?

Another property that keeps the liquids separate is that some of them are immiscible liquids, in other words they do not mix with each other. As you proved in the first experiment, oil and water are immiscible liquids. On the other hand, water and rubbing alcohol are miscible and will mix with each other. Water and the dishwasher liquid will also mix.

Stir up the liquids in the glass and watch what happens to the layers. Have any of the layers mixed (are they miscible in each other)? Wait a few minutes and look again. Have any of the other liquids separated?

Alternate procedure: Rainbow in a glass.

You will need the following materials:

• four different colors of food coloring (e.g. red, yellow, green, blue)
• five tall glasses or clear plastic cups
• ¾ cup (180 g) of granulated sugar
• a tablespoon for measuring
• 1 cup (240 ml) water

In the first glass, add one tablespoon (15 g) of sugar. In the second glass, add two tablespoons of sugar, three in the third glass, and four in the last glass. Then add three tablespoons (45 ml) of water to each glass, and stir until the sugar is dissolved. If the sugar in any of the glasses will not dissolve, add one more tablespoon (15 ml) of water to all of the glasses, and stir again. When the sugar is completely dissolved, add two or three drops of red food coloring to the first glass, yellow to the second, green to the third, and blue to the last glass.

In the remaining glass we will create our rainbow. Fill the glass about a fourth of the way with the blue sugar solution. Next, carefully add the green solution to the glass. Do this by putting a spoon in the glass, just above the level of the blue solution. Slowly pour the green solution into the spoon, raising the spoon to keep it just above the level of the liquid, until the glass is half full. Add the yellow solution, and then the red one in the same manner. What do you notice about the colored solutions?

The amount of sugar dissolved in a liquid affects its density. The blue solution has the most sugar dissolved in it and is therefore the densest. The other solutions are less dense than the blue solution, so they float on top of it. The densities of the solutions should be very close however, and the solutions are miscible, so you will see that the layers do not form well defined boundaries as in the first experiment. If done carefully enough, the colors should stay relatively separate from each other. What do you think will happen if you stir up the liquids in the glass?

The Fire Extinguisher

By David Arez
Escola Secundária de Loulé Portugal

This is movie about the functioning of carbon dioxide fire extinguishers.
If oxygen is removed by a gas that isn't combustive then the combustion reaction comes to an end.

Diffusion

Group 3 - Alexandru S, Darius O, Raluca B, Vlad M - Colegiul Naţional "Mihai Eminescu" Satu Mare, România

Air versus Water

A movie that gives a good idea of atmospheric pressure. Our atmosphere is capable of keeping a papel up even against a glass full of water. In fact, one would need a column of water with a height of about 10 meters in order to have equal water and air pressures.

Does smoke rise or goes down?

To make our experiment we need a bottle of plastic of 1´5 litres, a sheet of paper and a few matches.

First we make a couple of holes in the bottle of plastic, one in the top part and another one near the base of the bottle.

Them we take the sheet paper and cut away a rectangle of 10x15 cm (10 times fifteen). We coil the paper to obtain a small cylinder of approximately 15 cm of length. Finally the small tube of paper interferes for the top hole of the bottle.

On having ignited the small tube of paper with a match a small flame is formed and is observed that for another end of the bead goes out a column of very dense smoke that falls down inside the bottle. In the exterior scarcely there is smoke.

If we cover the low hole with a finger, the small tube of paper goes out and smoke doesn’t go out.

Explanation:

On having burned the small tube it departs from the paper it is clear in the shape of particles that, together with the gases that formed in the combustion and the air they form the smoke.

In normal circumstances, the smoke ascends dragged by the warm air of the combustion.

In our experiment, the smoke that takes place is produced in the interior part of the small tube travels along it. Inside the bottle, there is no warm air, so that, when the smoke goes out for the low end of the small tube there aren’t produced rising currents of convection and the smoke, denser that the air, it rushes to the bottom of the bottle.

by Clara, Beatriz and Inés

Spaghetti tightrope walker

Material: one spaghetti


1 Stand the spaghetti placed about your two hands.
2 It moves slowly one of the hands towards the other one without inclining the spaghetti.
3 Regardless of the hand that moves the two end up together in the center of the spaghetti that will remain in balance without falling.

Explanation:

By moving the hands, spaghetti slides without falling, keeping the gravity center between the fingers.

by Antonio and Antonio

A bottle with a hole

In order to make our experiment, we only need a bottle of water with it’s cap.

We make a small hole in a plastic bottle, about a half of its height, and we fill it full of water, while we are covering the hole.

If we remove our finger from the hole, no water comes out, but if we remove the cap of the bottle, the water starts to come out. But why?

If the cap is put, the internal pressure on the hole is equal to the external pressure and that’s why the water doesn’t come out of the hole.

But, if we remove the cap, we allow that the air comes into the top of the bottles, breaking the previous balance. The internal pressure on the hole is greater than the external pressure, so the water comes out of the bottle.

by Irene and Rafael

Fakir baloon

This is an experiment where we can see that if the same force is distributed over a bigger surface then pressure is smaller. Since what makes the balloon explode is pressure, the more "punaises" lesser will be the pressure exerted on the balloon. With only one "punaise" the balloon will explode.

Reaction of Sodium and Water

The helicopter

Cartesian Diver

Ball in the air

The air stream doesn't allow the ping-pong ball to fall.


http://www.youtube.com/watch?v=mExwPCvNRJ0

Explosion in the box

We prepared:

• a stand
• 2 empty plastic boxes; smaller and bigger so that one could be a kind of lid to the other
• a small piece ( ball) of calcium carbid ( not wet or old)
• water in the wash bottle
• matches

We made a little hole in the bottom of the bigger box. Then a piece of carbide was put in the box in such way so that the hole was higher ang water could be added on the carbide ball.
Carbide reacts with water and in the reaction we obtain a gas - acetylene C2H2:

CaC2 + 2 H2O = C2H2 + Ca(OH)2

Acetylene is flammable and it burns silently if it's pure. When it is mixed with air , explodes and throws away the upper box.



http://www.youtube.com/watch?v=A9QvpGiNgQw

Fire without matches

We carried out the experiment wich shows how to make a fire without matches.

We used potassium permanganate KMnO4 and glycerine C3H5(OH)3.

Be careful and wait while doing it, fire appears after several seconds.

http://www.youtube.com/watch?v=kpae8Xh90mI

Another balance with two forks a toothpick and fire

To make our experiment we need a pair of forks, a toothpick, a glass and a match.

First, we have to intertwine the forks with the toothpick and leave them in balance at the edge of the glass. The balance is obtained because the centre of the gravity is under the support point.

What would happen if we burnt the edge of the toothpick that is inside the glass?

A part of the toothpick is burnt, but the flame is put out when it’s at the edge of the glass and the balance of the forks is kept.

The loss of volume of the toothpick that is burnt, doesn’t affect to the centre of the gravity

by Teresa and Ángela

An eddy in a bottle

To make our experiment we need two plastic bottles of one and a half litres.

First, drill a hole in the two bottles corks.
Then, fill one of the bottles with water to about three quarters and join the two plugs per cylinder.
To unite the two bottles it can be used a tape.

It is very important the union between the bottles.

When the water on the bottles is empty is upper, it seems that the water does not fall easily to the bottle bottom, but if we give a circular motion to the bottle top and creates a swirling, water falls easily.

By placing the bottles on top, water doesn’t fall to the bottom because of the compressed air trapped in the bottle which is down. It can pass through it, as there is no room for it.

When the eddy is generated by moving the top bottle, it is communicated the air in both bottles and the water in the top bottle falls easily into the bottom bottle.

by Yulia

Drawing with sand

To make our experiment we needs a plastic bottle, sand beach and a rope.

First we have to construct a pendulum with the bottle.
Them we cut the base and make a couple of holes in one of the sides in order to pass the rope and another hole in the stopper to exit the sand filled.

If the bottle is away from the position of equilibrium it begins to oscillate, describing a trajectory that will be recorded in the soil by the stroke that left the sand that falls from the bottle.

Depending of the length of the rope and on the relationship between distances, we can get different figures.

The figures obtained are known as Lissajous figures, names after French scientist Jules Antoine Lissajous, who first observed this in 1857.

by Anabel and Teresa

The underwater drop

Materials:

1. A small container and a big glass.
2. Oil
3. Water
4. Alcohol
5. Glue and coin.
6. A spoon.

If the container is made of plastic, we stick a coin at its base in order to get more stability and avoid floating.

We fill the half a container with oil.
We put it at the bottom of the glass.
We pour the alcohol necessary to cover the container very carefully.

Then, we add water little by little with a spoon (it must slip from the wall of the glass).
Small container's surface filled with oil will adopt a convex shape until the water you add is enough. Then, the oil will separate from this container and it will have a spherical form that will remain just in the middle inside the oil and water mixture.

EXPLANATION:
First, we must know the densities of the liquids we use in the experiment.
- water (1g/ml)
- oil (0'92 g/ml)
- Alcohol (0'75 g/ml)

The oil floats in the water because it's less dense than water, but it sinks into alcohol because it's denser than it. In conclusion, you can prepare a mixture with alcohol and water because inside it, oil won’t float or sink.

by Ana, Marta and Belén

Union doesn’t make strength

The materials we need to do the experiments are a balloon and drawing pins.

First you have to push the balloon against twenty drawing pins and make sure they don't explode. The strength exerted has distributed on all the drawing pins so there isn’t sufficient pressure to explode the balloon.

The effect of strength doesn't depend only on its intensity, but also on the surface on which exerts. If the surface is very large, the effect of the strength will be spread over it all.

Next, push the balloon against one drawing pin and notice if it explodes. In this case, all the strength mass and pressure at a very specific point makes the drawing pins go through the balloon and explode.If on the contrary, the surface is small, the intensity of the strength mass over it is stronger and its distorted effect increases.

by Lourdes and Blanca

Does smoke rise or goes down?

To realize our experiment we need a bottle of plastic, a sheet of paper and a few matches.

First we do a couple of holes in the bottle of plastic, one in the top part and another one near the base of the bottle.
Then we take the sheet paper and cut away a rectangle of 10x15 cm.
We coil the paper to obtain a small cylinder of approximately 15 cm of length.
Finally the small tube of paper interferes for the top hole of the bottle.

On having ignited the small tube of paper with a match a small flame is formed and is observed that for another end of the bead there goes out a column of very dense smoke that falls down inside the bottle. In the exterior scarcely there is smoke.

If we cover the low hole with a finger the small tube of paper goes out and smoke does not go out.

Explanation:

On having burned the small tube it departs from the paper it is clear in the shape of particles that, together with the gases that are formed in the combustion and the air they form the smoke.
In normal circumstances, the smoke ascends dragged by the warm air of the combustion (currents of convection).

In our experiment, the smoke that takes place is produced in the interior part of the small tube travels along it.
Inside the bottle there is no warm air, so that when the smoke goes out for the low end of the small tube there do not take place (there are not produced rising currents of convection) and the smoke (denser than the air) it rushes to the bottom of the bottle.

by Francisco and Fernando

OIL POMP

Materials:
1 One small container and one larger glass
2 Oil
3 Water
4 Glue and one coin
5 Spoon
6 Alcohol

Assembly:
1. If the container is of plastic we put on the base one coin to give it stability and to avoid that it floats.
2. You take the small container, and you fill the container until the middle with oil and you see that the oil sets on the bottom of the glass.
3 Inside the glass you fill with precaution, the amount of alcohol that you need to cover the small container. Then with a spoon, you add, little by little, water.The surface of the oil from the small container will be more and more convex, when the water that you have added is the necessary, the oil will give off the container and will forma sphere that will be floating inside the mixture of water and alcohol.

Explanation:
The densities of the three liquids : water (1g/ml), oil (0,92g/ml) and alcohol (0,79g/ml).
The oil floats on the water because it is less dense than the water, but the oil doesn’t float on the alcohol because it is denser. So you can prepare one mixture of water an alcohol, where this oil won’t float and won’t sink until the bottom.

by Macarena, Irene and Sofía

A whirlpool in a bottle

Materials:


Two bottles made of plastic 1,5 l.
Insulating tape

Execution:

First, we make a 1 cm hole at the tops of the bottles. Then, we fill one of the bottles with 75% of water and join the bottles by means of the tops. To join the two bottles we use the insulating tape. This joint is very important, so do not be stingy with the insulating tape.


When the bottles with water is on top of the other, the water does not fall easily to the empty bottle, but if we make a circular movement with the upper bottles, it generates a whirlpool, and the water falls easily.

Explanation:

When we place the bottles full of water on the top, the water does not fall because of the low compressibility of the air, which takes up the lower bottle and does not let any space for the water to fall.
By the time, the whirlpool is generated by the air of the two bottles that passes from one to the other and the water of the upper bottle falls easily.

By Mercedes and Fátima

The extintor

Material:

- Sodium bicarbonate.

- Vinegar.

- A glass.

-Matches

- A candle

Frame up:

Put inside a glass a little of vinegar ( three or four centimetres)
Add a little sodium bicarbonate. Then many bubbles appear.
Light a candle with a match. If you tilt the glass without spilling vinegar, we see that the candle puts out.


Explanation:

The chemical reaction between sodium bicarbonate and acid vinegar producers a gas called Carbon Dioxide. This gas is heavier than the air and it stays in the glass by moving the air in the glass.
When you put the candle next to glass it´s turned off by the lack of oxygen. When you tilt the glass, it´s put out because the carbon dioxide, displace the oxygen that retain the combustion.

by José Ángel and Miguel

Ruler and newspaper

To make our experiment we need a ruler made of plastic, a sheet of newspaper and a heavy object.

First we place the ruler on a table so that the middle part of the ruler is on the edge of the desk. If we drop a heavy object on the part that stands out we see that the ruler falls down from the table.

We repeat now the experiment by placing a newspaper sheet extended on the part of the ruler that is on the table. If we draw now the same object on the part that stands out we see that the ruler doesn't fall to the floor.

What makes the ruler stop? Is it an invisible hand or perhaps the weight of the newspaper sheet?

The correct answer is the pressure and the strength in the atmosphere on the newspaper sheet.

It´s very easy and you can do it at home. Will you do it there?

by Marta and Claudia

The water that is not wet

To make the experiment we need:

1) A glass
2) A piece of paper
3) A big countainer with water

We have to fill a countainer with water, then we put a piece of paper at the botton of the glass so that, it won´t fall when we turn it down. Later,we turn round the glass and we put it with the paper into the borron of countainer. It´s so important not to till the glass.

Finally, we take the glass out of the countainer and we check that the piece of paper isn´t wet.

The explanation is quite simple the air contened into the glass blocks the water to enter and arrive to the piece os paper which is at the botton of the glass.

by Marta and Isabel

Candy chromatography

Group 5 - Elena B, Cynthia C, Karina L, Laura P - Colegiul Naţional "Mihai Eminescu" Satu Mare, România

Ever wondered why candies are different colors? Many candies contain colored dyes. Bags of M&Ms or Skittles contain candies of various colors. The labels tell us the names of the dyes used in the candies. But which dyes are used in which candies? We can answer this by dissolving the dyes out of the candies and separating them using a method called chromatography.

For this experiment you will need:

• M&M or Skittles candies (1 of each color)
• coffee filter paper
• a tall glass
• water
• table salt
• a pencil(a pen or marker is not good for this experiment)
• scissors
• a ruler
• 6 toothpicks
• aluminum foil
• an empty 2 liter bottle with cap

Cut the coffee filter paper into a 3 inch by 3 inch (8 cm by 8 cm) square. Draw a line with the pencil about ½ inch (1 cm) from one edge of the paper. Make six dots with the pencil equally spaced along the line, leaving about ¼ inch (0.5 cm) between the first and last dots and the edge of the paper. Below the line, use the pencil to label each dot for the different colors of candy that you have. For example, Y for yellow, G for green, BU for blue, BR for brown, etc.

Next we’ll make solutions of the colors in each candy. Take an 8 inch by 4 inch (20 cm by 10 cm) piece of aluminum foil and lay it flat on a table. Place six drops of water spaced evenly along the foil. Place one color of candy on each drop. Wait about a minute for the color to come off the candy and dissolve in the water. Remove and dispose of the candies.

Now we’ll “spot” the colors onto the filter paper. Dampen the tip of one of the toothpicks in one of the colored solutions and lightly touch it to the corresponding labeled dot on your coffee filter paper. Use a light touch, so that the dot of color stays small - less than 1/16 inch (2 mm) is best. Then using a different toothpick for each color, similarly place a different color solution on each of the other five dots.

After all the color spots on the filter paper have dried, go back and repeat the process with the toothpicks to get more color on each spot. Do this three times, waiting for the spots to dry each time.

When the paper is dry, fold it in half so that it stands up on its own, with the fold standing vertically and the dots on the bottom.

Next we will make what is called a developing solution. Make sure your 2-liter bottle or milk jug is rinsed out, and add to it ⅛ teaspoon of salt and three cups of water (or use 1 cm3 of salt and 1 liter of water). Then screw the cap on tightly and shake the contents until all of the salt is dissolved in the water. You have just made a 1% salt solution.

Now pour the salt solution into the tall glass to a depth of about ¼ inch (0.5 cm). The level of the solution should be low enough so that when you put the filter paper in, the dots will initially be above the water level. Hold the filter paper with the dots at the bottom and set it in the glass with the salt solution.

What does the salt solution do? It climbs up the paper! It seems to defy gravity, while in fact it is really moving through the paper by a process called capillary action.

As the solution climbs up the filter paper, what do you begin to see?

The color spots climb up the paper along with the salt solution, and some colors start to separate into different bands. The colors of some candies are made from more than one dye, and the colors that are mixtures separate as the bands move up the paper. The dyes separate because some dyes stick more to the paper while other dyes are more soluble in the salt solution. These differences will lead to the dyes ending up at different heights on the paper.

This process is called chromatography. (The word “chromatography” is derived from two Greek words: "chroma" meaning color and "graphein" to write.) The salt solution is called the mobile phase, and the paper the stationary phase. We use the word “affinity” to refer to the tendency of the dyes to prefer one phase over the other. The dyes that travel the furthest have more affinity for the salt solution (the mobile phase); the dyes that travel the least have more affinity for the paper (the stationary phase).

When the salt solution is about ½ inch (1 cm) from the top edge of the paper, remove the paper from the solution. Lay the paper on a clean, flat surface to dry.

Compare the spots from the different candies, noting similarities and differences. Which candies contained mixtures of dyes? Which ones seem to have just one dye? Can you match any of the colors on the paper with the names of the dyes on the label? Do similar colors from different candies travel up the paper the same distance?

You can do another experiment with a different type of candy. If you used Skittles the first time, repeat the experiment with M&Ms. If you used M&Ms first, try doing the experiment with Skittles. Do you get the same results for the different kinds of candy, or are they different? For example, do green M&Ms give the same results as green Skittles?

You can also use chromatography to separate the colors in products like colored markers, food coloring, and Kool-Aid. Try the experiment again using these products. What similarities and differences do you see?

LUDION

MATERIALS:
-A plastic bottle
-Transparent tube of a pen
-Insulating tape and scissors
-Elastic rubber
-Clips

MAKING OF:
1. Fill the bottle with water.
2. Cover one hole of the pen with insulating tape. If the pen has got a lateral hole, it has to be covered too.
3. Join the clips to the pen with the elastic rubber, in order to float with the open hole inside the water.
4. Close the bottle.

When you press the bottle, you can see how the pen goes down to the bottom of the bottle. When disminising the pressure, the pen goes up again.

EXPLANATION:
Pascal's and Archimedes' Principle allow us to explain the experiment.
Before pressing the bottle, the pen floats due to its weight is smaller than the thrust power made by the water.
When you press the bottle, the pressure is transmitted to the bottom of the pen and the water enters in the bottom, so its produces an increasement of the pen's weight (the aire is sustituted by the water)When the weight is higher to the thrust, the pen sinks.
When you stop pressing, the water comes off and the pen goes up.

by Julia and Begoña

Extinction a candle

Materials needed: a glass -vinegar -sodium bicarbonate a candle lit The working In a glass place vinegar (3-4cm). Add a spoon of sodium bicarbonate. The two substances produce a reaction. Expected to leave the foam obtained. Meanwhile, light a candle, then take the glass with vinegar and bicarbonate and we approach the candle not let the liquid fall to the flame. Explanation: Candle is extinguished due to gas produced by the two

Tritean Elena, Nichilciuc Claudia

Scoala Gimnaziala "Gheorghe Lazar" Zalau (Romania)

Water pressure

Horea H, Andrei M

Scoala Gimnaziala "Gheorghe Lazar" Zalau (Romania)

Hot air, cold air

Horea H, Andrei M

Scoala Gimnaziala "Gheorghe Lazar" Zalau (Romania)

Ballon not exploding

Oroles Jidav, Lavinia Pop, Aurelia Campean, Vlad Drulea

Scoala Gimnaziala "Gheorghe Lazar" Zalau (Romania)

Vlad si Alex

Scoala Gimnaziala "Gheorghe Lazar" Zalau (Romania)

The descomposition of oxigenated water

Materials:

- Oxigenated water
- Blood
- Some matches
- A glass

To realice our experiment we need oxygenated water (of sale in drugstores) and a few milliliters of blood. If we defrost a piece of meat in a plate, we can obtain sufficient blood to realize our experiment.

We add blood to a glass with oxygenated water and see that a chemical reaction takes place with gass emission that forms a white foam. The oxygenated water descomposes, due to blood, in water and gaseous oxygen (that forms the white foam). We can recognize the oxygen if we bring a match over.

You can see that the sparkles of light take place due to the combustion of the oxygen caught in the white foam.

The oxygenated water is used as disinfectatn when it begins on a wound. The blood contains one enzyme that acts as a catalyst, accelerating the reaction descomposition of the oxygenated water. As many of the pathogenic bacteria are anaerobic (they can´t live with oxygen), they die in the white foam (rich in oxygen) that takes place when the blood of the wound acts on the oxygenated water.

Density column

The Colour of Fire

Group 8 - Liana R, Andrada S, Alexandru S, Octavian L, Darius O - Colegiul Naţional "Mihai Eminescu" Satu Mare, România

Materials used: filter paper, tong, Berzelius glass, a spirit lamp, matches, chemical substances: SrCl₂, CuSO₄, KClO₃

First we prepared solutions dissolving the substances from above in water. We put a filter paper in each solution and then we let them dry for about two days. Then, with the tongs, we put each filter paper above the spirit lamp and the flames burned with different colours.

Another balance with two forks a toothpick and fire

To make the experiment we need two forks, a toothpick, a glass and a few matches.

We entwine both forks with the toothpick and leave the set in balance in the edge of a glass. The balance is achieved when the gravity center of the set is below the point of support.

What does happen if we burn the end of the toothpick that is inside the glass?

A part of the toothpick burns but the flame goes out when coming at the edge of the glass and the balance of the forks is kept. The loss of mass of the toothpick that has burnt not affect significantly the gravity center that continues below the point of support.

By Inma and Pía

Resonnance in wine Glasses

MATERIALS

To make a wine glass sing, you will need the following materials:

1. Wine glass - a crystal, thin-walled one works best.
2. Separate glass or jug
3. Water

PROCEDURE

To make the wine glass sing, do the following:

1. Fill the empty glass or jug with water.
2. Add the water to the wine glass
3. Wet the index or middle finger of your hand with some water.
4. Lightly rub your wet finger along the rim of the glass.
5. As you rub the glass, you will hear the "singing" sound of the glass. You may have to re-wet your finger periodically and/or adjust the pressure of your finger on the rim of the glass to keep producing the sound.
6. You can change the pitch of the sound by adding water to the glass.

EXPLANATION

Every material (such as glass, steel…) has a natural frequency at which it vibrates, called a resonant frequency. Resonance is a physical phenomenon that occurs when a body is capable of vibrating under the action of a regular force. Its period of vibration coincides with the period of vibration characteristic of that body. In these circumstances, the body vibrates increasing gradually the amplitude of vibration after each of the subsequent actions of the force.
The cup vibrates with a determinate frequency and tone. If more water is added to the wine glass the tone becomes lower.

by Mª del Mar y Blanca

Atmospheric Pressure and Hydrostatic Pressure

Clasa a VII-a D, Şcoala "Mircea Eliade" Satu Mare, România

The backwash of colours

Main objective of lab: To see how the surface tension causes the food colourings to swirl in the saucer.

Materials used
Milk*Food colouring (4 colours) *A saucer *
The backwash of colours (Vartej de culori): Add a drop of each colour to the*Fill the saucer with milk *Detergent Methods: Add one drop of detergent to the center of the saucer
Results: The colours milk swirl in the saucer

Medina B., Bogdan D , Scoala Gimnaziala "Gheorghe Lazar" Zalau,Romania

Atmospheric pressure

To perform this experiment we need a boiled egg, bark, matches and a bottle with his mouth wider. First light match, is inserted in the bottle and let them burn. Bark boiled egg and place over the mouth of the bottle. After put the eggs, match is extinguished, and the eggs begin to pass the mouth of the bottle until it reaches the. Because the eggs covered the mouth of the glass to match the fire consumed all the oxygen in the bottle, and after it was extinguished. Explanation: Because of the lack of oxygen pressure and body weight decreases with pressure acting on the outside glass egg that "leaking" through the mouth bottles.

Breje Diana, Festeu Cristina, Hara Paula, Vidrasan Emanuela

Scoala Gimnaziala "Gheorghe Lazar" Zalau, Romania

Snake chimical

Solution of silver nitrate; copper wire

A ball that floats

Materials: To make our experiment we need a light ball ping-pong and a hairdryer. Uscătorul start and leave the ball in the air. Depending on the weight of the ball remains suspended it closer or further away from dryer.
Explanation phenomenon that took place: The explanation seems simple experiment. Upward flow of air from the dryer generates a pressure force which compensates the weight of the ball. This allows the ball float in the air.
Observations:
The speed of air leaving the dryer increases in the central and lower edges. In regions where the air is moving with greater speed and low pressure, and regions where the air has a lower speed is high pressure. When the ball is moved slightly from the central part of the current, generates a difference in pressure pushes the ball back to the center of power.

Bora Dan, Puscas Lavinia, Marincas Matei, Breje Georgeta

Scoala Gimnaziala "Gheorghe Lazar", Zalau, Romania

Colored Smoke

Materials used (to smoke one): - 8g K (NO3) - 6G sugar- 3g of food coloring, powder (use more colors) - 1.5 g of sodium bicarbonate - Source of heat (gas, electric furnace, etc.). - Container for mixing ingredients, resistant to high temperatures, metal (pan, vessel of metal, etc.). - A spoon (or something for. Mixed metal) - Small cardboard tube (diameter approx. 1.25 cm and 2 cm) and a switch to plastic - Lint (from fireworks, ca. 2.5 cm) - Little plastelină

Method of preparation: - Mix the following ingredients: -K (NO3), sugar, color and bicarbonated sodium - The substance is produced in a pan - Put the pan into the fire, and mix until the substance becomes omogenizează as peanut butter (be careful not to become too dark in color) - The substance is obtained with the spoon and put in the cardboard tube in the middle of his stick, until about the middle height tube, beţişorul plastic and leave it so until the mixture strengthens after strengthening to remove, carefully beţişorul - In the hole left by the switch fuse is inserted and in addition it put plastelină the cardboard tube removed, using a knife, with great care * smoke obtained is placed on a heat resistant material * light the fuse and see a spectacular game of colors and lights WARNING: during the whole experiment will wear protective equipment and heating the ingredients will not be made in cash or in any room!

Bode Bianca , Lascu Iulia , Gudea Casian

Scoala Gimnaziala "Gheorghe Lazar" Zalau, Romania

Oxidation of apples

Materials: An apple A lamiae A transparent foil Ice Four plates
Working mode: Cut four pieces of apples. In each plate by putting a piece of apple. During the first plate put a simple piece of March In the second plate put a piece of March infoliata In the third plate put another piece of March over the add lemon juice In the last dish put a piece of ice in March Shot in ten in ten minutes, and at last, after thirty minutes are stage four pieces of apples.
Observations: After each 10-minute video and I noticed that the apples are oxidised gradually, Whether the materials used. After thirty minutes I noticed that the piece of oxidised Tuesday is simple.
Explanation phenomenon that took place:Oxidation is a chemical reaction that occurs Marului contact with oxygen in the air. In our experiment can be seen easily as color becomes more closed to supraafata contact. Apples oxidation can be delayed with ice and a transparent foil so that the apples do not come into contact with oxygen. Another method to retard oxidation is to add a little lemon juice. Lemon juice contains vitamin C which acts as an antioxidant. Therefore in many restaurants salatele fruit containing a little lemon juice to help not rust.
Conclusions: For this experiment we concluded that apples should be cut not left much time in direct contact with oxygen (02).

Puscas Lavinia , BoraDan , Marincas Matei ,Breje Georgeta , Pah Dana, Pop Giorgiana, Rus Raluca, Turcas AlexandraScoala Gimnaziala Gheorghe Lazar", Zalau, Romania

Condensation in glass

To make our experiment we need a plastic bottle of 1.5 liters, a sheet of paper and some matches. First is a pair of holes in the plastic bottle at the beginning and another near the glass. Then take the sheet and cut a rectangle of 10x15 cm. Roll of paper for a small cylinder about 15 cm long. Finally the tube is inserted through a hole above the paper bottle. When you turn on the tube of paper with a match is made and a small flame is observed, on the other end of the tube leaving a dense column of smoke, falling into the bottle. On the outside, no smoke. If you cover the bottom hole with a finger to see how the smoke comes out next paper. Explanation: By burning the tube portion of the paper is apparent in the form of particles with gases that are formed during combustion and the air is smoky. Under normal circumstances, the smoke is drawn to the burning hot air (convection currents) In our experiment, the smoke that is produced inside the tube along its journey. Inside the bottle is not hot air, so that when smoke comes out the bottom end of the tube there is no convection and upwelling of smoke (more dense than air) precipitates at the bottom of the bottle.

Barnutiu S, Blaga A, Gaidos C, Chira F, Temes C

Scoala Gimnaziala "Gheorghe Lazar" , Zalau, Romania

Action on the spirit egg

Materials; A plate of iron A fresh-egg A bottle of alcohol The working Put the tray in spirit, not too much, then break the eggs and we put in tray and let alcohol act Observations after 10 minutes to observe the effect of alcohol and gets the eggs begin to albeasca. After 30 minutes, the eggs start easy, easy to prajeasca, and after 45 minutes is totally fried. Explaining the phenomenon Egg is a food product after contact with spirits (flammable liquid), the eggs begin to prajeasca like when fried in oil. Conclusions Depending on the method applied I noticed that the eggs can be fried in alcohol without having contact with fire.

Pop Georgiana, Turcas Alexandra, Pah Dana, Rus Raluca

Scoala Gimnaziala "Gheorghe Lazar", Zalau, Romania

Action of vinegar on the shell egg

Materials - 1 egg -200 Ml vinegar (acetic acid) -1 Bol The working Put the eggs in vinegar in bol, after which the liquid drop in 24 hours Observations After several hours we see how the shell egg is inmoaie Later Note how the shell away from the egg, floating on the surface of liquid Finally, the remaining egg shell burst, reaching in egg yolk vinegar Explanation phenomenon that occurred Vinegar, a food, is an acid that acts on calcium carbonate from egg shell. Because decomposing shell egg is back, finally arriving in egg yolk vinegar.


Georgiana P, Alexandra T, Dana P, RalucaR

Scoala Gimnaziala "Gheorghe Lazar" Zalau, Romania

Vulcan Chemical

To build it you need: 100 g-flour, 5 tablespoons aracet-50-g salt, 6 newspapers. 1.Mai first newspapers to break in pieces and then put them in a bucket 2.Puneti water from newspapers to fill the dish and a towel covering them. 3.Le left soaking in a night. 4.Pe boards of a size of A3 sheets paste a bottle. 500ml cut at the top. 5.a day they stoarceti water and make a composition that will stick. 6 After composition, begin to build up near the glass ii dati a suitable form.

Hudin Horatiu; Margin Horea ;Trestian Vlad;Negrea Sebastian;Margin Ionut

Scoala Gimnaziala "Gheorghe Lazar" , Zalau,Romania

Vulcan Chemical_Eruption

Eruption: the glass in place until the half. vinegar and bicarbonate food. To get lava you can use colored or red coloring yellow.

Warning! Do not make rash supervised by the teacher!

Hudin Horatiu; Margin Horea ; Trestian Vlad; Negrea Sebastian; Margin Ionut

Scoala Gimnaziala "Gheorghe Lazar" , Zalau, Romania

Atmospheric & Hydrostatic pressures

Group 4 - Maria B, Cezara V, Antonia T, Anca G - Colegiul Naţional "Mihai Eminescu" Satu Mare, România

For this experiment you will need: a glass, a sheet of paper, water
The glass must be filled with water and covered with a piece of paper, so that the paper is tight to the edge of the glass. Keeping the palm of your hand over the paper, the glass is turned upside down and the palm is removed. If you kept the air from entering the glass by the paper, this would stick to the glass and the water does not flow out. If the air entered into the glass, the experiment will not succeed!

Atmospheric and Hydrostatic Pressure_MariaB

Publish at Scribd or explore others: How-To Guides & DIY experiments

An eddy in a bottle

In order to make our experiment we needed two plastic bottles of 1´5 liters.

In the first place, we perforated a hole of 1 cm in the corks of the two bottles. Soon we filled one of the bottles with water until approximately three fourth parts and if united the two bottles by the corks. In order to unite the two bottles insulating tape can be used. Is very important a good union between the bottle.

When the bottle with water is on the empty bottle it is observed that the water does not fall easily to the inferior bottle, but if we give a circular movement to the superior bottle is generated an eddy and the water falls easily.

When placing the bottle in the superior part, water does not fall by the little compressibility of the air locked up in the inferior bottle that does not leave space to the water that falls. When the eddy is generated when moving the superior bottle, it is put in communication the air that is in both bottles and the water of the superior bottle falls easily in to the inferior bottle.

Colegio Sagrado Corazón (Esclavas)
Sevilla (Spain)

Tin´s race

In order to make this experiment you need the following materials:

1. An empty softdrink can.
2. A baloon. If we don' have, we can use expanded polystyrene (white cork)

In order to continue with our experiment we make the following procedure:
1. Blow up the baloon.
2. Rub the baloon against your hair or a wool article (for example a scarf).
3. Put the softdrink can knocked down on a table and we approach the baloon. After doing this, we can check that the softdrink can move!

Explanation:
This happens because when rubbing the baloon electricity loads. The attractive electrical forces between the loads or different signs of the baloon and the softdrink can make the tin rotates.

Colegio Sagrado Corazón (Esclavas)

Sevilla (Spain)

un monde..de réfléxions...UN MONDO DI …………………..RIFLESSIONI !

Cette scène de théatre continue l'histoire qu'on a dèjà commencée..
c'est un dialogue sur les miroirs..avec un tel Monsieur Albert (Einstein???)
Vous la lisez en italien car elle est proposée par la prof de Physique italienne M.me Teresa Seu et ses élèves.
Les élèves Italiens qui étudient les LV vont bientot travailler cela et en faire des B.D numériques!
Vous le lisez pour l'instant en italien..on vous le proposera en espagnol et en français très bientot!

UN MONDO DI …………………..RIFLESSIONI !




Un miroir est une surface suffisamment polie pour qu'une image s'y forme par réflexion. C'est souvent une couche métallique fine, qui, pour être protégée, est placée sous une plaque de verre pour les miroirs domestiques (les miroirs utilisés dans les instruments d'optiques comportent la face métallique au dessus, le verre n'étant qu'un support de qualité mécanique stable).

L'adjectif relatif au miroir est spéculaire car il permet de voir ...
On peut se voir en utilisant le reflet à la surface de l'eau (comme Narcisse) ou dans une vitre ; dans ce cas la réflexion est partielle tandis qu'avec un miroir parfait la réflexion est totale.

On peut aussi obtenir de la réflexion totale lorsqu'un rayon passe d'un milieu d'indice de réfraction élevé vers un milieu d'indice faible, sous une incidence rasante ; par exemple lorsqu'un rayon passe de l'eau dans l'air, ou bien du verre dans l'air. Cette propriété est utilisée pour les prismes à réflexion totale.

Lorsque l'on dit que la surface d'un miroir doit être polie, cela signifie qu'aucun défaut n'est acceptable afin que toute la réflexion de l'onde incidente se fasse dans la direction voulue. La taille du défaut visible est de l'ordre de la longueur d'onde de l'onde électromagnétique. Ainsi, avec la lumière visible, les défauts doivent être plus petits que 0,01 μm, ce qui est très contraignant techniquement. En revanche, avec les ondes utilisées par la télévision, le défaut doit être plus petit que 0,1 mm seulement, ce qui explique que les paraboles de télévision (qui sont des miroirs permettant de concentrer, de focaliser les ondes émises par les satellites) soient rugueuses à l'œil et sous la main ; elles sont en revanche parfaitement lisses pour les ondes hertziennes. Pour les radars, l'ordre de grandeur du défaut admissible est de l'ordre du cm, on peut donc utiliser un grillage comme miroir ; Il en est de même que pour certains radiotélescopes.

( source: WIKIPEDIA)

Miroirs..Miroirs..









SCENA N. 1 Dialogo tra Clotilde e Fedora






Clotilde Ti ho portato un regalo per il tuo compleanno!




Fedora Grazie, uno specchio da borsa, che bello!




C. Osserva bene, da una parte ti vedi normale, dall’altra parte invece vedi il tuo volto ingrandito.




F. E’ vero! Come può accadere questo?




C. Non ne ho idea. A dire la verità non ho mai capito neppure come funzione uno specchio normale! Perché gli oggetti sembrano essere “dentro “ lo specchio? E perché se sono davanti a una parete non vedo niente?




F. Non ci ho mai pensato. Però mi piacerebbe capire come funziona uno specchio.




C. Tra l’altro hai notato che ci possiamo specchiare anche in altri oggetti? Nelle vetrine, nelle finestre ( non sempre però), nelle palline dell’albero di Natale, in una superficie di acqua.




F. Sai che facciamo? Il nostro amico Albert studia al Liceo Scientifico e una volta mi ha raccontato che a Fisica hanno studiato proprio gli specchi. Andiamo a chiedergli spiegazioni?




C. Ok! Andiamo! Tra l’altro Albert è molto simpatico e …….anche bello!







SCENA N. 2 A casa di Albert



F. Ciao Albert! Ci è venuto il desiderio di capire come funzionano gli specchi. Ci spieghi qualcosa, tu che sei un “genio” ?

A. Non c’è bisogno di essere geni per comprendere queste cose ! Se studiamo la Fisica possiamo capire tanti fenomeni che accadono intorno a noi. Per questo io sono così appassionato di questa materia! Cominciamo!




Prima di tutto dobbiamo capire cosa significa “ vedere “ un oggetto, ………







A

per esempio una penna, che vi disegno come se fosse una freccia . occhio

Da ogni punto della penna, ( prendiamo il punto A) , arrivano ai

nostri occhi dei raggi di luce




C: Ma una penna non è una lampadina!




A: E’ vero, ma la penna rimanda in tutte le direzioni la luce che proviene dalla sorgente, in questo caso la lampada, che la illumina e che la colpisce , così come fa la luna che rimanda verso la terra parte la luce del sole da cui è illuminata.

Il nostro cervello capisce che l’oggetto si trova esattamente nel punto dove convergono, cioè dove si incontrano, i raggi di luce che arrivano all’occhio. Così, punto dopo punto si costruisce la visione dell’oggetto.

F: Ok, questo è chiaro. Ma gli specchi?




A: Un po’ di pazienza. La luce quando colpisce una superficie viene riflessa con una regola ben precisa; se guardate il disegno ( che rappresenta il cammino di un solo raggio di luce) tutto ciò è molto chiaro : l’angolo di incidenza è uguale all’angolo di riflessione


raggio incidente raggio riflesso






















angolo incidenza angolo riflessione




Se facciamo buio e osserviamo un pennellino di luce che colpisce lo specchio tutto questo è molto evidente.

E’ esattamente quello che accade, ad esempio, quando una palla da biliardo colpisce la sponda del tavolo.




C : E’ vero, mio padre è molto bravo a biliardo, e sa prevedere con precisione dove andrà a finire la palla anche dopo molti rimbalzi; egli conosce esattamente il modo con cui le palle rimbalzano sulla sponda.




A: Dunque consideriamo un oggetto che si trova davanti a uno specchio e fissiamo prima l’attenzione su un solo punto ; dal punto escono tanti raggi di luce che colpiscono lo specchio e si riflettono secondo la legge della riflessione di cui abbiamo parlato. Ne ho disegnati solo due per chiarezza














Ora se una persona sta davanti allo specchio e i suoi occhi vengono colpiti dai raggi riflessi, il suo cervello prolunga i raggi e “ crede” che provengano da un punto dietro lo specchio e così localizza, “vede” il punto dell’oggetto proprio dietro lo specchio. Così si forma l’immagine del punto esattamente nella posizione dove convergono i prolungamenti dei raggi riflessi.

Ovviamente dietro lo specchio non c’è luce vera, ma solo i prolungamenti “immaginati” dei raggi riflessi: per questo l’immagine si chiama virtuale.

Per ogni punto dell’oggetto accade la stessa cosa, cosi si costruisce l’immagine dell’intero oggetto.

Si può vedere, e anche dimostrare facilmente, che l’immagine si trova in posizione simmetrica rispetto allo specchio.




F: Sei stato molto chiaro, credo di aver compreso perché ci riflettiamo “dentro” gli specchi. Sembrerebbe quasi una magia, ed invece è spiegabile abbastanza facilmente con le leggi della fisica.




C: Sì, però non mi è ancora chiaro perché tutto questo non accade quando mi trovo davanti a un muro o davanti a un’altra superficie qualunque.




A: Te lo spiego subito. Un muro non ha una superficie perfettamente liscia come uno specchio. Quindi i raggi si riflettono sempre secondo la legge della riflessione, ma incontrando una serie di superfici con direzione diversa “ rimbalzano “ in modo disordinato, e i raggi riflessi non sembrano provenire da un punto unico; così non si forma l’immagine. In questo caso si parla di diffusione.











C: Ora mi sembra che sia tutto chiaro.




F: Però, Albert, ci sono ancora due cose che non ci hai spiegato:

perché qualche volta ci riflettiamo anche nei vetri delle finestre, ad esempio, ma non sempre?

perché in alcuni specchi ci vediamo più grandi?




A: Ok, vediamo il primo punto. Ti trovi davanti a una finestra : il vetro è trasparente e la maggior parte della luce che proviene dal tuo corpo lo colpisce e passa dall’altra parte. Solo una piccola parte viene riflessa . Ora, se entra dalla finestra molta luce dall’esterno, perché ad esempio è giorno, questa la luce intensa copre la luce riflessa che proviene dal tuo corpo e quindi la tua immagine non è visibile. Se invece fuori è buio, la luce che ti arriva dal vetro è solo quella riflessa e allora puoi vedere la tua immagine quasi come se ci fosse uno specchio.

Per il secondo punto invece la cosa è un po’ più complessa da spiegare e lo potremo fare meglio un’altra volta. Possiamo dire però brevemente che occorre uno specchio curvo, ( lo specchio migliore è quello parabolico). La luce che colpisce lo specchio segue sempre la legge della riflessione , ma trovando una superficie non piana, i raggi si riflettono in modo diverso, e si può formare, con opportune condizioni, una immagine più grande, come si vede bene dal disegno (AB è l’oggetto, A’B’ la sua immagine ingrandita). Vi è sufficiente questa spiegazione?

occhio




Clotilde : Sì, grazie, è stato molto interessante e anche divertente.

Sembra incredibile,vero, che una lezione di Fisica possa essere divertente ! Possiamo tornare qualche altra volta a chiederti altre spiegazioni?




Albert : Certo, mi fa molto piacere. Ciao e a presto!



MIROIRS!

"