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Light: Shadows and Reflections

How much light gets through?

A bathroom window lets daylight in. You cannot see who stands outside. Why?

A torch beam meets a clear plastic bag. The screen behind stays bright.
Step 1 of 3
  1. A torch beam meets a clear plastic bag. The screen behind stays bright.
  2. A thin cotton sheet lets some light through. The screen is dim.
  3. A floor tile lets none through. The screen shows no patch.

The glass lets light in, but blurs what is outside.

The new words

  • Transparent — you see clearly through it.
  • Translucent — you see only a blur through it.
  • Opaque — you cannot see through it at all.

The rule

An opaque material blocks all the light. A transparent material lets nearly all of it pass. A translucent material lets part of it pass.

Opaque things make a dark shadow. Translucent things make a faint one.

Now try it. Guess the word first. Then look at the screen.

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This track

  1. 0 Start here
  2. 1 Light travels in straight lines
  3. 2 A shadow is a place light did not reach
  4. 3 How big, and what shape
  5. 4 A hole makes a picture
  6. 5 Light bounces off a smooth surface
  7. 6 What you see in a mirror
  8. 7 Why a wall shows you nothing
  9. 8 Checkpoint: straight lines, shadows and mirrors
  10. 9 Does it make its own light?
  11. 10 How much light gets through?
  12. 11 A simple periscope uses two mirrors
  13. 12 The big picture
  14. 13 Track quiz

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