YOU NEED:

• Proximity to a photocopying machine
• Some paper

  Myriad optical illusions are created when figure are drawn on a disk and it is rotated slowly. Here is how you can try it. Use a photocopying machine to copy the square shown in the illustration with the three nested ovals. Cut the square out and crease it along both diagonals (dotted lines) to form two “valley” creases ( that is creases that go inward when viewed from above). Now open the square and flatten it you will find the creases from a point at the centre which allows the square to rotate. Now put the square on a surface which is smooth yet hard. Begin to rotate very slowly with a fingertip on one corner. The concentric ovals will become deformed as through they are made of rubber. HOW DOES IT WORK? Psychologists are baffled by this illusion. A more...

You can amaze friends with this amusing illusion when you are a in a department store where there are square pillars with tall mirrors on all four sides. You will have to be wearing a hat. Stand as shown in the illustration so that half your body projects from the side of the mirror. The reflection of this makes you appear normal. Your friends will be floored. You will seem to slowly lift both legs until you seem to be suspended in midair. At the same time you hat rises mysteriously several feet above your head! HOW DOES IT WORK? Actually what you do is raise you one visible leg, and with your hidden arm, doff your hat. Even adults will be taken aback by this classic mirror illusion.

YOU NEED:

• A saw
• A playing card

  The sound of a reed instrument like a clarinet or a saxophone, is the result of the vibration of a reed. Vibration of the air creates sound in wind instrument like violins, comets and trombones. Again in musical instruments like violins or cellos the sound is created because of friction between the bow and the string. The pitch of the sound depends on how fast the vibration is .  This is amply demonstrated if the edge of a playing card is rubbed against the teeth of a saw. If you rub the card slowly it produces sound at a lower pitch which increases in crescendo when the card is moved faster. HOW DOES IT WORK? There is no difference between the manner in which vibrations are created when a card is rubbed against the cutting edge more...

Has this ever happened to you that you were watching a cricket match on the televison and you let out a cheer when a player hit the ball over the fence. Try it. Stand as far away from the television set as possible, then cheer as loudly a possible. You will notice that, when you do this the sound distorts the picture on the screen. It seems as if the vertical hold in the television is malfunctioning.   HOW DOES IT WORK? Surprisingly the cheer you let out has no effect on the television screen whatsoever. The strong vibration of the sound you have just made rattles your eye and it creates a strobe effect influencing your vision of the television screen’s scanning beam. This is what creates the blurring effect.

YOU NEED:

• A glass of water
• A small coin
• A table

  Do you know that you are capable of making a coin simply disappear. Fill a clear glass, with straight sides, with water. Put it on the table and then place a coin about six inches (15cms) behind it. Once viewed through the glass, one will see two coins lying side by side. Now close one of your eyes- Lo! One coin will vanish! HOW DOES IT WORK? Light passing through a glass of water causes refraction" which means its path is bent. This causes objects to appear to be in a different position than in reality. In this experiment for instance, one eye sees the coin directly, while the other gets to see the refracted image of the coin which seems to be in a different position. The effect is that you more...

YOU NEED:

• A soft pencil
• A sheet of paper
• A piece of tape
• A glass of water

Firstly rub a soft pencil point back and forth to create a black area of graphite. Rub your thumb over the spot so that you have graphite on your thumb. Now press the tip of your thumb against the sticky side of the cellophane tape. Hold the tape up to the light to see a clear thumb print. Secondly put a full glass of water on a table. When the water settles down, press a thumb firmly against the side of the glass which is nearer to you. Now bend your head till you can view the tip of the thumb through the water. The ridges of the thumb will be clearly visible. HOW DOES IT WORK? A thumb print comprises of tiny ridges. The cellophane tape more...

YOU NEED:

• White cardboard
• Scissors
• A sharpened pencil stub
• Felt – tip – pen

  Cut a circle about six inches (15 cm) in diameter from a piece of white cardboard. Make a hole in the middle and push a sharpened pencil stub through it to make a top. Take the felt – tip pen, and draw a black circle on the disk as in the illustration. Guess what you will see you spin the top? You will see small concentric circles and that too, two of them!   HOW DOES IT WORK? The illustration reveals that XY drawn the diameter through the middle of the small circle, will intersect it at pots. As the disk spins, the spots move in almost a straight line compared to other spots along the little circle. The eyes see them for a longer time so as to more...

YOU NEED:

• Two mirrors
• A tomato or any other object

  Place two mirrors on a table face to face situated one foot (30cm) apart. Place a tomato halfway among the mirrors. The tomato's images form endless reflections in the mirrors. The question is: If you bring the tomato closer to one of the mirrors, will the two closest images come nearer, further away, or remain in the same place? Try to figure out the answer to this. HOW DOES IT WORK?    It does not matter where the apple is placed between two mirrors, the two closest images will have be two feet apart- For instance, if the apple is moved to a position which is one inch (2.5 cm) from one mirror, its image in that mirror will be two inches (5 cm) from the apple. Its image in the more...

YOU NEED:

• A small drill
• A bottle
• Water colour
• Adhesive
• Some ice

  Insert a tube through a small hole drilled through cork. Fill a bottle with coloured water. Cap the bottle with the cork. Seal the joints with adhesive to make water tight. The rise in water level in the tube is measure of temperature. Stand the bottle in icy water mark the level of water in the tube as 0 degree. Make markings of other temperatures by comparing with a doctor's thermometer. Place the entire apparatus in the sun for a few hours. Check the water level in the tube, it would have risen. HOW DOES IT WORK? As the colured water in the bottle heats up, it expands and flows upwards into the glass tube. This process gets reversed as the water cools. Mercury thermometers work in the same manner.

YOU NEED:

• A bouncing ball made of hard rubber
• A table

  Here is a trick to amuse your friends. You can tell them you have discovered a way by which you can throw the ball in such a way that it will halt in midair, turn directions, and come to you. Your friends would like to see this trick. It is not difficult to procure a bouncing ball made of hard rubber. You can get it a shop selling sports goods or even at your neighborhood store. A little spin on such a ball makes it bounce. Now try this on table  that is standing on a hard surface. Throw the ball as  shown in the ''illustration by the arrow marks. The ball will hit the table's underside; reverse its direction and bounce back to you.     HOW DOES IT WORK? As more...