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Science project idea

Toy shadow length: does a higher torch make a shorter shadow?

The length of a shadow depends on where the light is. A high light gives a short shadow and a low light gives a long one, like the Sun at noon and in the evening.

Make it yourself8 numbered steps, the materials and the science, all free.Go to the stepsGet a ready-made kitReady-made models, kits and spare parts in the store under Physics.Browse PhysicsAsk on WhatsAppAsk the head office whether a model or kit for this idea is available.Send a message

What it shows

The length of a shadow depends on where the light is. A high light gives a short shadow and a low light gives a long one, like the Sun at noon and in the evening.

The science

Light travels in straight lines. When the torch is low, rays hit the toy at a slant and reach far along the paper, so the shadow is long. When the torch is high, the rays come steeply and the shadow is short. The Sun does the same through the day, giving long shadows in the morning and evening and short ones at noon.

Materials

Cost: free. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.

  • A small toy or a clay figure about 5 cm tall
  • A torch (free)
  • A big sheet of paper or the floor
  • A ruler
  • A pencil
  • A stack of books to raise the torch

Safety

For this project: No special safety. Do not shine the torch into eyes.

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 rules

Step 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.

  1. Stand the toy on the paper and darken the room.

  2. Place the torch on the paper about 30 cm from the toy, pointing at it.

  3. Mark the end of the shadow with a pencil and measure its length with a ruler.

  4. Put the torch on one book and keep the distance the same.

  5. Mark and measure the new shadow.

  6. Add another book and measure again.

  7. Write the three lengths in a small table.

  8. Say what happens to shadow length as the light gets higher.

What you should see

The shadow gets shorter each time the torch is raised, just like the shadow of a tree at noon.

Viva questions

A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.

1When is your own shadow shortest?

At noon, when the Sun is high.

2Why is the shadow long when the torch is low?

The light hits at a slant and reaches far.

3What did you keep the same?

The toy and the distance of the torch.

4Why do we measure with a ruler?

So the length is a fair number we can compare.

Free ebook: Viva Questions for Science Projects

Take it further

Measure your own shadow in the playground at morning, noon and evening.

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.

Free ebooks for this project

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