What can you see?

What can you see?

Try this experiment and find out!

What you need:

  • A cardboard tube
  • A sheet of card
  • Scissors
  • Sellotape

How to:

Ask an adult for help with using scissors.

  1. Cut out a circle of card that is wider than the end of your cardboard tube.
  2. Cut a long, narrow slit in the card. It should be around 2.5 cm long and 0.3 cm wide.
  3. Stick the cardboard circle over the end of the cardboard tube. The slit should be in the middle.
  4. Look through the open end of the cardboard tube, using only one eye. You might find it easiest to close your other eye. Hold the tube so the slit is vertical and keep the tube still. What do you notice?
  5. Now, look through the tube and move the tube slowly across the room. Move the tube faster and faster. What do you notice?

Man holding telescope_101403674_proc

Look through the cardboard tube. What do you see?

What did you see?

When the tube is still, you can't see much. You can only see through the narrow slit. When you move the tube quickly from side to side, you can see a lot more.

What's happening?

Your brain remembers an image for around 1/30th of a second. When you move the tube from side to side your eye sees lots of narrow images. If you move the tube fast enough, your brain remembers the images long enough to build up a big image. Clever, right?

Try it on your friends and parents!

Curriculum information

  • Summary

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    Curriculum key wordsOther web links
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