What it shows
A shadow forms when something blocks light. The nearer the object is to the light, the bigger and softer the shadow is.
The science
Light travels in straight lines. When your hand blocks the light, the wall behind has no light on it and we see a dark shape called a shadow. If the hand is closer to the torch, it blocks a wider cone of light, so the shadow is bigger. Moving the hand closer to the wall makes the shadow smaller and sharper.
Materials
Cost: free. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- A torch (free)
- A plain wall in a dark room
- Your hands
- A paper and pencil to record
Safety
For this project: Do not shine the torch into anyone’s eyes. An adult must be present in a dark room.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesStep by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Darken the room and place the torch about one metre from the wall.
Hold your hand between the torch and the wall and see its shadow.
Make a bird, a rabbit or a dog by folding your fingers, and look at their shadows.
Bring your hand closer to the torch and watch the shadow grow bigger.
Move your hand close to the wall and watch the shadow get smaller and sharper.
Ask a friend to guess your animal from the shadow only.
Draw the shadow when your hand is near the torch and when it is near the wall.
Say where the light is blocked and where it passes.
What you should see
Shadows of your hand look like animals, grow when your hand moves towards the torch and shrink when it moves towards the wall.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1What is a shadow?
A dark place where an object blocks the light.
2Why does the shadow grow near the torch?
The hand blocks a wider part of the light.
3How does light travel?
In straight lines.
4Can we get a shadow without light?
No, we need light.
Take it further
Make a shadow puppet from card on a stick and put on a short play.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
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