Archives September 2012

  • Some white card
  • A used candy stick
  • Some glue
Cut four sheets of white card each measuring about 250mm. square. Make a crease in the centre of each card and fold each sheet down the centre. Draw a picture of a person without arms on a separate piece of Trace this image and transfer it to all the cards. On one card add the arms on the sides, on two cards draw the arms outstretched and on the last card draw them lifted upwards. Paste the halves of the pictures as shown in the diagram so that the two pictures with outstretched arms are between the other two. Glue a candy stick through the middle. When you spin it, the speed makes it seem as if the still pictures are joined and the man is exercising.

  • A small paper cup
  • Some string
  To make a paper cup squawker make tiny hole at the bottom of a paper cup. Push a thread through the hole and tie a knot on one end as the illustration. Hold the cup in one hand. Wet the fingers of your other hand and pinch the hanging thread just below the cup. Now slide down the thread. The cup will make an astonishingly loud squawking sound!   HOW DOES IT WORK? The fingers create just the right amount of against the thread. The thread is caught and many times a second once you slide your down. The string vibrates rapidly and that in turn forces the bottom of the cup to vibrate. Once this happens, the surrounding air vibrates, which is heard as a loud squawking sound. The sides of the cup actually work like a more...

  • A party mask
  • Paint
  • A lamp or any other source of light
  Scare the wits out of your friend. Use the Party Mask to create a scary optical illusion. Use crayons, water colours or other hues of paints to colour lips red, cheeks pink, and eyes blue. Darken the eyebrows. Hang the mask on the wall, painted side out. Direct light at it, from a lamp placed below. Step away a few yards. It will look like a normal face rather than one turned inside out. Now make a sideways movement. Horror of horrors! The face will sway from side to side as you move. It always face you seeming to turn. HOW DOES IT WORK? This one is the most eerie of all optical illusions. The light from the lamp placed below is not necessary, but it helps to strengthen the convexity of the mask. The more...

  • A torch
  • A mirror
Prop a mirror against the wall and place your drawing board in front of it. Tape the front of a torch with some opaque insulation tape in such a way that you leave just a slit on the glass, about 4 mm wide, for the light to come out. Draw a  line perpendicular to the mirror in the centre of the board. Place the torch facing the mirror, as shown in the illustration and switch it on. Use drawing pins to track the path of the light, from the torch, on the drawing board. Do  the same for the light reflected off the mirror. On examination you will find that the path taken by the light from  the torch and off the mirror forms equal angles on either side of the line you had drawn on the drawing board.

  • Two paper cups
  • A long piece of string
  • Toothpicks or wooden matches
  To make a paper cup telephone pierce a hole at the bottom of one cup. Now insert one end of the string through the bottom of the cup and pull it out from the open end of the cup. Tie the string to the middle of a match stick or a toothpick. Do likewise with the other end of the string Inside the second cup. The string will have to be long enough to allow two people to stand far apart, keeping the string taut. You have to ensure that the match stick or the toothpick is firmly pressed against the bottom of each cup. Now,  one person speaks into one cup while the other person holds the other cup to his ear and listens. Vibrations created at the bottom of the cup by the speaker, are transmitted more...

  • A shoe box
  • Plastic  tracing  paper
  Take a shoe box, with black colour, paint the insides and the lid black. Cut out a square window on one and paste tracing paper over the opening thus a screen. On the opposite side of the box, make a small hole. Place a small object on the table, shine the light of a lamp on it. Point the viewer towards the object: Light rays from the object travel in straight lines and intersect each other as they pass through the viewer. If you look at the screen on the other side you will see an upside down image of the object.

  • A white wall
  Stare at the centre of the picture in the illustration even as you count slowly till 100. Now look aside and stare at a white wall.  What you will see is a startling image of a young boy playing with a steam engine. The apparition that you have just seen is known as an afterimage. The retina in your eye tires of seeing black and white, and for a few moments when you look at the wall, it reverses black and white. If you happen to stare at a colour picture, its afterimage will change the colours to their complements. If you stare at a red apple for a minute or two, lo you will catch a glimpse of a green apple on the white wall. Gaze at an orange, and there will be a blue one on the wall.

  • A coffee mug
  • A paper with printing on it.
  • Mylar mirror
  • Glue
  Another way to make a mirror which does not reverse is to place two ordinary mirrors at right angles to each doesn't know who the first person was to think of the following delightful way to demonstrate the  properties of such a curved mirror. Take a coffee mug with cylindrical sides as in the illustration. On one side of the, mug, on its inside base, glue a piece of paper with printed words on it. At the top of the mug, directly opposite, glue a rectangle cut from the Mylar mirror paper. When you look at the reflection of the printing in the Mylar,  you will find that the printed words read normally. HOW DOES IT WORK? In an ordinary mirror, light is reflected straight back at you from more...

  • 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.


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