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Light and the Electromagnetic Spectrum

Why objects appear coloured

  • 2 things to know
  • Paper 1

Overview

Why objects look red, white or black in white light, what a colour filter transmits and absorbs, and how books, shirts and cars appear when seen through filters or lit by coloured light.

What you need to know

Answer each one before you reveal it.

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Key term

Explain why a blue car looks almost black under an orange street lamp.

Key term

Compare the light leaving a red filter with the white light entering it.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Explain why a red book looks red in white light.

    Model answer

    Its surface absorbs the other colours in the white light and reflects red light to the eye.

  2. 2

    Explain why an object looks white in white light.

    Model answer

    Its surface reflects all the colours of visible light roughly equally.

  3. 3

    Explain why an object looks black.

    Model answer

    Its surface absorbs all the colours of visible light and reflects almost none.

  4. 4

    Describe what a colour filter does to the light passing through it.

    Model answer

    It transmits its own colour and absorbs the other colours.

  5. 5

    State the colour a red book appears when it is viewed through a green filter.

    Model answer

    It appears black, because the filter absorbs the red light the book reflects.

  6. 6

    State the colour a white shirt appears when it is lit only by red light.

    Model answer

    It appears red, because red is the only colour available for it to reflect.

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