Trick Of The Light: Wow The Kids With These Simple Torch Effects

Light and shadow are magical things to play with. All you need is a bright light (most smartphones now have one), a dark room, and a bit of imagination. Here are six simple ideas to have fun with a flashlight.

By the way, this article uses ‘torch’ in the British sense, to mean flashlight. Do not try any of these tricks with a blowtorch. That would be reckless.
 

This is the easiest shadow game in the book -- all you need is a torch or smartphone with a bright light. Place the torch or phone on the floor, with the lit bulb pointing upwards. Now, position your hand about a metre above the light so it casts a silhouette onto the ceiling. Wiggle your fingers and make spooky noises as you gradually move your hand closer to the bulb. The shadow will get steadily larger, as though the hand is getting closer! The effect also works well with feet and heads.

“I can do any shadow puppet you like, so long as it’s a rabbit, a dove, or a kind of scrunched up face.” If you share my feeble repertoire, then consider bringing in some outside assistance. Traditional shadow puppets use only the hands to cast silhouettes of animals. But why stop there? Grab any toys or objects with distinctive profiles and stick them in front of your torch. Alternatively, cut out interesting shapes from card, like the family in our top image. You can use the effect to tell stories, or play a game of “guess the toy from its shadow”. They’ll never guess this one…

Now you’re projecting toys, take things to the next level by making drawings. Here, you’ll need to cast your shadows onto a sheet of white paper or card (unless you don’t mind the kids drawing straight onto the wall). Our earlier article provides plenty of tips and inspiration for making shadow drawings and how to use the idea to teach a bit of science.

What do we reckon? It seems, intuitively, like shadows should always appear black or grey. But it’s not so. You can easily prove this by getting hold of some coloured cellophane or translucent Lego blocks. Anything that’s vaguely see-through and coloured will work. When you shine a torch through the object, its shadow will appear coloured. Technically, it’s not a shadow (which is an absence of light) but filtered light. However, the effect is the same. 

There’s an even cleverer way to create colourful shadows. For this, you’ll need to find three bright bulbs of different colours (preferably red, green and blue). If you point these in the right way at a white wall, it’s possible to create multiple colourful shadows at the same time. You’ll find numerous videos on YouTube that show how to do this, and why it happens… but can you work it out?

Gotham City is in peril. Only one person can help. BatChild! Rig up your very own bat signal with everyday materials. All you need is an old crisp tube (e.g. Pringles). First, eat all the crisps. This is very important. Now, take the translucent lid and paint a bat shape onto it -- you may need oil paints for this. Alternatively, cut a bat shape from card and glue it onto the lid. Place the lid back onto the tube and remove the bottom. Now all you need to do is shine a light through the tube and the bat signal will project onto the ceiling. Note: may not be powerful enough to project onto the rolling bank of fog that perpetually shrouds this benighted city.

And now for something completely different… You can use shadows for an unforgettable lesson in science and mathematics. This works best on older children. First of all, ask them to try to imagine a four-dimensional object. Naturally, they won’t be able to do this. But you’re going to show them a gateway to the fourth dimension using shadows. 

First, get an effectively one-dimensional object like a knitting needle or thin pencil (something with length, but not much breadth or depth). Shine the torch end-on to the needle, so it casts a dot onto the wall or the ceiling. You then explain that a one-dimensional object casts a zero-dimensional shadow (a dot). Now take a two-dimensional object like a sheet of card. Cast your torch onto its edge to project a line onto the wall. “A two-dimensional object,” you then say, “casts a one-dimensional shadow”. Now ask what they expect to happen with a three-dimensional object. If they’re paying attention, they’ll tell you it’ll cast a two-dimensional shadow. And, lo, a torch shining on any 3-D object, like a ball or a box, will project a two-dimensional shadow onto the wall, with height and width but not depth.

So here’s the big reveal. You tell your kids that to find a four-dimensional object, all they have to do is look out for something that casts a three-dimensional shadow. Simple. (They’ll never succeed, of course, but this exercise in abstract thinking will stay with them a long time.)

See Also

The science of light for KS2 kids
17 Diwali crafts for kids