# A Science Project on Diffraction

The process of bending of light when passing around an edge or through a slit is called diffraction. A demonstration of diffraction can be easily done by using a candle or small bright flashlight and a slit made with two pencils. The diffraction pattern (a pattern of dark and bright bands of light) which is created as the result of this experiment proves that light has wave like properties.

### Aim:

The aim of this science fair project is to demonstrate diffraction.

### What you need?

1.      Two pencils (new and of equal length)

2.      A transparent tape

3.      A candle

### How to go about it?

1.      Light the candle and make the tiny lamp to shine brightly.

2.      Just below the eraser, wrap one layer of tape around the top of one of the pencils.

3.      You can calculate the wavelength of light emitted by the candle or bulb, if you can measure the distances on the diffraction pattern.

4.      The light should be kept at least half a meter away from you.

5.      With the erasers at the top, hold the two pencils vertically. Make a thin slit between the pencils just below the tape. The skit will be formed because the pencils will be slightly apart due to the tape wrapped around one pencil.

6.      Hold the pencils at a distance 1 inch away from one eye. Then you will be able to see the slit between the pencils and look at the light source through the slit. Try to make the slit smaller by bringing the pencils together. Watch the line of light perpendicular to the slit. Rotate the pencils until they become horizontal by looking through the slit. Notice that the line of light becomes vertical.

7.      By looking closely to it, you can see that the light is composed of tiny bright and dark bands of light. These bands of light grow larger and spread apart when you try squeezing the slit together. You can also see it moving away from the central light source and becoming easier to see. The blobs will have blue and red edges and they will be closer to the light source.

8.      Stretch a hair tight and place it about 1 inch away from you eye. Start moving the hair and hold it between your eye and the light source. Because of the hair you can see the light is spread into a line of blobs, just as it was by the slit. Now watch the line of blobs rotating by rotating the hair.

9.      Watch the light through a piece of cloth, a feather, a diffraction grating, or a piece of metal screen. While looking through it, rotate each object.

### What happens?

The black bands between the bright bands of light show that there is a wave associated with the light. When the light passes through the slit, they spread and the light waves interfere with each other. When the crest of a wave interfere with the crest of another a bright band of light is formed whereas when a crest overlap with the trough of another wave they cancel out and as a result a dark band is observed.

The angle at which the light bends is proportional to the wavelength of the light. For instance, red light has a larger wave length than blue light and so the red light bends more than the blue light. Thus the coloured edges are produced by the different amount of bending; blue on the inside and red on outside.

# Build a Homemade Periscope

The aim of this simple science fair project is to make a periscope using simple materials

### Materials Required for the project:

1. Two similar pocket mirrors
2. A box or a pipe of 50 centimeters length (The length of the pipe can be increased in proportion with that of mirrors)
3. A knife or suitable cutting material
4. A pencil or a marker
5. Transparent tape

### Procedure for the project:

1. Cut a hole of 2cm diameter at a height equaling half that of the mirrors from the bottom side of the box.
2. Now turn the box so that the hole cut is at the bottom of the opposite side facing you.
3. Mark a point at a distance equaling half that of the mirrors from the top of the box and cut a hole of 3cm diameter there.
4. Place the mirrors in the box as shown in the figure using the transparent tape.
5. Now look through the small hole and you can see the objects ahead.

# Rock Candy Science Fair Project

### Aim:

The aim of this science project is to make your own rock candy.

### Materials Required:

1. A piece of string (20 cm long)
2. One cup of water
3. A medium sized bead (should not float in water)
4. A small metal rod or a pencil
5. Two cups of sugar
6. A glass jar
7. A Pan

### Procedure:

1. To one end of the string tie the bead and tie the other end to the middle of the pencil or rod
2. Place the pencil horizontally on the edges of the glass jar (See pictiure) and adjust the hanging length of the thread so that it won’t touch the bottom or the side of the glass jar.
3. Now pour the water into the pan and boil it
4. Add 1/4 cup of sugar into the boiling water and dissolve it.
5. Add some more sugar and dissolve it. Repeat this till the boiling water is saturated with sugar. (That is when you can dissolve no more sugar)
6. Pour this hot sugar solution into the glass jar
7. Place the pencil over the jar as we did earlier
8. Allow the solution to cool without any disturbance
9. Observe each day and see how the crystals are growing on the string.
Note: This is a lengthy experiment. It may take one week to see full crystal growth.

# Bouncing Ball Experiment – A Fun Science Project

### Aim:

To understand the law of conservation of energy using a simple experiment.

### Materials required:

1.      A tennis ball.

2.      A knife.

### Procedure of the project:

1.      Drop the tennis ball from a height on to the floor. Simply drop and do not throw it. Observe how the ball bounces back but not quite up to the point from which it was dropped.

2.      Now use the knife to cut the tennis ball into two hemispheres. The trim the halves so that each one is a little smaller than a hemisphere.

3.      Turn one half inside out and drop it from a height. You will see that half ball rebounds higher than the point from which it was dropped.

### Scientific explanation:

When the ball is dropped, it does not rebound up to the initial height due to the effect of the law of conservation of energy which states that energy can neither be created nor destroyed, but only changed from one form to another. When the ball is held at a height, it has potential energy. When it is dropped and it hits the ground, this potential energy is converted into kinetic energy of motion and some amount of heat upon hitting the ground. As some energy is lost as heat, the kinetic energy of the ball is not as much as the earlier potential energy. Hence it does not rebound quite up to the dropping point. Now when the half of the ball is turned inside out, the energy required to turn it inside out is stored as potential energy in the ball. When the half ball hits the ground this potential energy is released and changed to kinetic energy. Therefore the half ball rebounds higher than the point from which it was dropped. The law of conservation of energy is still obeyed in this case.

# Spill Water- Simple Test on Cohesion

### Aim:

To observe the phenomenon of cohesion in liquids by a simple experiment using water.

### Materials required:

1. Some water.
2. A glass or cup.
3. Some pins.

### Procedure:

1. Fill the glass or cup to the brim with water. Fill just enough so that it doesn’t overflow but a little more will surely make it overflow.
2. Gently put on pin into the cup horizontally. Observe the increase in water level.
3. Add more pins. You will see that the water level will increase and rise above the brim but still doesn’t overflow.
4. Keep adding pins till finally one pin makes the water overflow.

### Scientific explanation:

All matter has a force called cohesion between its particles. Cohesion is the force of attraction between similar or like particles or molecules. It is strongest in solids, which is why solids remain in one shape always. It is weaker in liquids and the weakest in gases, which is why gases are completely free if not closed tightly in a container. In this experiment the water molecules stick to each other by cohesion and do not spill over even when you add a few pins. But after a number of pins, the force of cohesion in water is not strong enough to keep it from overflowing and at this point the water spills over the brim.

# Prove that Light Consists of Multiple Colors

In physics we learn that natural light is a combination of seven colours. This science fair project is to prove that theory by separating colors from light.

Aim:

Demonstrate that light consists of seven colours.

Materials Required:

1. A triangular glass prism.
2. A source of light (a candle or a bulb)
3. A cardboard box with one side open
4. A piece of white paper

Procedure:

1. Make a hole of 1″ at the center of any side adjacent to the open side of the cardboard box.
2. Paste the white paper to the inside of the cardboard box opposite to the hole
3. Place the triangular prism inside the box so that it comes between the hole and the white paper. Make sure the prism is lying on one of its lateral faces.
4. Place the source of light adjacent to the hole.
5. Adjust the prism and the light source so that the light falls on one side of the prism
6. You will now observe rainbow colors on the white paper.

# How to Make a Kaleidoscope

### Aim:

To build a basic Kaleidoscope to see colourful 3D patterns.

### Materials required:

1. Some duct tape.
2. Some coloured paper
3. A pair of scissors.
4. Glue.
5. Three pieces of glass mirror.

### Procedure:

1. Buy a glass or acrylic mirror of 1/6or 1/8 inch dimension from a shop and have them cut the mirrors into small pieces of 12 inch length with a width of 2 inches at the narrow end and 7 inches at the other end. Get three such identical pieces. Do not try to cut the mirrors yourselves as it is dangerous.
2. Using the tape to join the three pieces together with the reflective sides facing inwards.
3. Stand under a light and place your hand under the narrow end of the kaleidoscope while you look in through the wide end. You will see your skin monstrously stretched across the mirrors.
4. Next place the smaller end on your eye and have your friend look in through the other end while you move your eye from side to side. Your friend will see a spherical monster covered with eyes which are swerving crazily around.
5. Cut up small pieces of coloured paper and put it into the kaleidoscope. Keep the narrow end against a tabletop and watch through the other end while rotating it. You will see beautiful patterns in 3D.

### Scientific explanation:

A Kaleidoscope is a device which operates on the principle of multiple reflections. Using several mirrors which are joined together, a number of beautiful patterns can be seen if coloured objects are put inside the Kaleidoscope and viewed while rotating. A three mirror model provides a 3D pattern.

# Density Tower Experiment

### Aim:

The aim of this science fair project is to make a density tower.

### What is density tower?

A density tower is a column of different liquids which are immiscible with each other. Since these liquids are immiscible they form different layers in the liquid column accodring to their densities.

### Materials Required:

In this experiment we are creating a four column density tower. The materials required are:
1. Tall but narrow glass container. A graduated cylinder used in your chemistry lab will do.
2. 1/4 cup of vegetable oil
3. 1/4 cup of rubbing alcohol
4. 1/4 cup of water
5. 1/4 cup of honey
6. a piece of cork
7. a rubber ball (small one)
8. a metal bolt
9. a grape

### Procedure:

1. Pour honey into the graduated cylinder upto 1/4 of its height.
2. Pour water into the cylinder upto 1/2 its height.
3. Now pour vegetable oil till it reaches 3/4th of the height of the cylinder.
4. Pour rubbing alcohol into the cylinder till it is almost full.
5. Add the objects one by one into the cylinder
6. Observe the liquids and objects in it.

### What do you see?

You will now see that the liquids are now divided into different layers with the denser liquid at the bottom. Also you can observe that the objects are now suspended at different layers of liquids according to their densities.
Note:
While pouring liquids into the cylinder make sure that you pour them along the cylinder wall so as not to disturb the liquid below. Avoid any disturbances to the liquid column.

# Balancing a Stick on Your Finger

### Aim:

To demonstrate the phenomenon of rotational inertia using a circus trick.

### Materials required:

1.      A two or three feet long stick or ruler.

2.      Some clay.

### Procedure:

1.      Take the stick and attach the clay as a lump near one end.

2.      Try to balance the stick on your index finger at the end which is nearer to the lump of clay.

3.      Next, try to balance the stick on your finger at the other end that is the end farthest from the lump of clay. Observe at which end it was easier to balance. You will find it easier to balance when the clay is at the top end and not near your finger.

### Scientific explanation:

An object has more inertia when its mass is more. In this case the end of the stick with the lump of clay has more mass and hence more inertia. When the heavy end is at the top, the inertia of the mass tries to hold it where it is and resists the gravitational pull which pulls it sideways for an instant. Hence you get time to adjust your finger accordingly in this time and keep it balanced.

# Can Crushing Experiment – Crushing a Can with Air Pressure

You might have experienced that on windy days it is difficult to keep the cycle steady. The cycle tends to move in the direction of the wind. It is one these days that we feel the pressure of air. On any other day the pressure of air is rarely felt. If the pressure inside and outside a body is same there is no effect on the body. If you have filled air into a cycle tube more than it can handle, it bursts. It is because the pressure inside the tube is relatively higher than the outside pressure. Do you know what will the case if the outside pressure is very much in excess relative to the inside temperature? We shall try out an experiment to try for ourselves.

### Aim:

To understand the pressure of air

### Materials Required:

1. An electric heater to heat water
2. A pair of tongs
3. A big sauce pan filled with cold water
4. Aluminium can

### Procedure:

1. Drop a tablespoon of water into the Aluminium can.
2. Place the can on the heater and heat it. You will see water vapours coming out of the can.
3. Take the can from the heater using tongs and place it upside down in the saucepan.(the opening of the can should face the water, watch the video.)
4. The can collapses instantly.

### Result:

The can collapses with immediate effect.

### Why did the can collapse?

As the can was being heated, the air inside the can was pushed out by the vapour. As soon as the can was put in cold water, the vapors condensed instantly creating an area of vacuum inside the can. Since the pressure outside the can is significantly higher it crushed the can.