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Description

Make a pinhole camera using recycled materials

Resources

Quick version:
toilet roll cardboard tubes (1 for each Cub),
greaseproof paper/tracing paper and foil cut into pieces a few cm larger than the tube end,
elastic bands/tape,
pins or sharp pencils
for testing: two light sources of different colours set up in a darkened space (e.g. head torches/bike lights running white and red light)

Longer version:
Empty Pringles Tubes with lids, Gaffer tape, Tin foil, Thumb tack or similar, Sharp knife and possibly white tissue paper.

Instructions

Your eyes, and the eyes of many other animals and insects, work the same way as a pinhole camera. Building your own pinhole camera will help you understand how this works.

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Quick version:

Use elastic bands/tape to cover one end of the toilet roll with tracing paper and the other with the foil. Make a small pinhole in the foil using a sharp pencil or pin (remember the hole can always get larger, but it is difficult to make it smaller). Cubs use camera to look at two lights set apart in darkened space. The colours will be reversed on the tracing paper "screen" as light reaching it travels in straight lines and must travel through the hole. This will be easier to explain if you draw a ray diagram showing the two lights, hole and screen.

Extra challenge: Explore other things (e.g looking at bright source when in darker environment), investigate the effect of making the hole bigger, use different lengths of tube.

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Longer version

Take an empty Pringles Potato Chip can and wipe out the inside so it is clean. Cut off the bottom two inches of the can with a sharp knife (you might need your mom or dad to help with this part).

The short piece has a metal bottom. Use a thumbtack to make a tiny hole in the center of the metal bottom. That's where the light will come in: it's like the black pupil in the center of your eye.

You're going to use the plastic lid as a screen, like the movie screen that the picture projects on to, or like the retina inside your eye. If the plastic lid on your can is translucent (light comes through but you can't see through it), you're good to go. If it's transparent (you can see through it), then you should tape a piece of wax paper or tissue paper to the lid.

Put the lid on the short piece, to make a short Pringles can. Now put the longer piece on top of the lid, so you have an open Pringles can with the lid blocking the middle of it. Tape it all together.

You need to keep all the light out of your camera, so roll your tube in some tinfoil twice around, and tape the foil on. Tuck the end of the foil over the open end of the tube. (You can also add a foam soda can holder over the open end of the can, to help keep light out.)

Take your camera outside on a sunny day. Hold the open end of the camera up to your eye. Make the inside of the tube as dark as possible. Can you see an upside-down picture of the outside on your plastic screen? Your eye also makes upside-down pictures on your retina, but your brain learns to flip the pictures right-side-up without your even thinking about it.

There is also an alternative design using a shoebox (or similar) attached.

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