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Auralith Learning

Year 8 · Science · Light and sound · Lesson 4

Refraction, colour and the eye

Refraction of light, dispersion by a prism, why objects look coloured, coloured filters, and the parts of the eye and what they do.

Whiteboard video lesson: Refraction, colour and the eye

23-minute video lesson

Teaching, worked examples and 20 practice questions solved step by step.

Watch free for a month

What your child will learn

  • Describe and explain refraction
  • Describe dispersion of white light
  • Explain the colours of objects in different lights
  • Explain how filters work
  • Label the eye and describe each part's job

The method

  1. Refraction: light bends when it changes speed; into glass it bends towards the normal.
  2. A prism disperses white light into a spectrum: red, orange, yellow, green, blue, indigo, violet.
  3. Objects reflect their own colour and absorb the rest; filters transmit their own colour.
  4. Eye: cornea and lens focus light on the retina; the optic nerve carries signals to the brain.

Key words: refraction, normal, prism, dispersion, spectrum, filter, absorb, retina, lens, cornea.

Worked examples

The first three practice questions from the lesson, with every step.

Question 1

A ray goes from glass into air at an angle. Which way does it bend? Why?

  1. Step 1: It speeds up in air
  2. Step 2: Bends AWAY from the normal

Answer: Away from the normal, because it speeds up

Question 2

A ray hits a glass block along the normal (at 90° to the surface). Does it bend?

  1. Step 1: Along the normal: no change of direction

Answer: No, it goes straight through

Question 3

Why does a swimming pool look shallower than it really is?

  1. Step 1: Light from the bottom refracts at the surface
  2. Step 2: Our brain thinks light travels in straight lines

Answer: Light refracts as it leaves the water, so the bottom looks higher