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Science lesson plan · 7th grade (Year 8 in England) · 60 minutes

Colour, prisms and refraction

Light, sound and waves

CCSS NGSS.MS-PS4-2England: KS3 Physics: Waves (light waves)England: KS4 Combined Science: Light and electromagnetic waves

Objective and success criteria

Students will: Colour, prisms and refraction.

  • I can answer questions on today's skill on my own, without help.
  • I can explain each step and say why it works.
  • I can check my answer and spot a mistake.

Before and after

Needs first: Reflection of light

Leads to: The electromagnetic spectrum; Refraction: refractive index, Snell's law and critical angle

Materials: Slinky or rope, Mirrors and torches, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 6 min

  • Quick retrieval from earlier learning (Reflection of light). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. A ray of light hits a flat mirror at an angle of incidence of 50° (measured from the normal). What is the angle of reflection? → 50 °Prompt: The law of reflection compares the two angles.
  2. A ray of light hits a mirror. The angle between the ray and the mirror surface is 60°. What is the angle of reflection (measured from the normal)? → 30 °Prompt: The normal is at 90° to the mirror.
  3. Which surface reflects light best to form a clear image? (a rough wooden board / a sheet of paper / a smooth, shiny mirror / black velvet) → a smooth, shiny mirrorPrompt: Smooth surfaces reflect light in one direction.

Hook · 6 min

  • Ask the class to make a wave with a rope or slinky and describe what moves and what doesn't.
  • Share the objective: Colour, prisms and refraction. Read the success criteria together.

I do: model it · 12 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: Why does a red apple look red in white light?
  • Step 1: Coloured objects reflect their own colour and absorb the rest.
  • Step 2: So the answer is: It reflects red light and absorbs the other colours
  • Answer: It reflects red light and absorbs the other colours
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 12 min

  • Do these together. Students try each step on whiteboards before you reveal it.
  • Use the hints as prompts rather than giving the answer.
  1. What colour does a green leaf look under only red light? (green / red / white / black (very dark)) → black (very dark)Prompt: A green object reflects green light only.
  2. Colour and light: which statement is NOT true? (Black objects absorb most of the light that falls on them. / Light slows down when it enters glass or water. / White objects absorb all colours. / White light is a mixture of colours.) → White objects absorb all colours.Prompt: Does a filter add colour or take colours away?

You do: independent practice · 17 min

  • Students work on the student sheet. Circulate and check the first two answers of every student early.
  • Students who finish: write a question of their own for a partner, with the answer.

The 6 questions are on the student sheet below, with answers in the key.

Exit ticket · 7 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. What colour does a green leaf look under only red light? (white / green / red / black (very dark)) → black (very dark)Prompt: A green object reflects green light only.
  2. Colour and light: which statement is NOT true? (Light travels at the same speed in glass as in air. / A red filter lets red light through and absorbs other colours. / Black objects absorb most of the light that falls on them. / White light is a mixture of colours.) → Light travels at the same speed in glass as in air.Prompt: Does a filter add colour or take colours away?

Watch out for

  • Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
  • Remembering facts without the reason: ask "why?" and "what is the evidence?"

Support and stretch

Support

  • Review first: Reflection of light.
  • Use concrete materials: slinky or rope.
  • Give the first step of each question, or a partly worked example to finish.
  • Pair with a confident partner for the guided practice.

Stretch

  • Move on to: The electromagnetic spectrum; Refraction: refractive index, Snell's law and critical angle.
  • Explain a common mistake in writing and how to fix it.
  • Write a word problem that uses today's skill, then solve a partner's.

Homework and more practice

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-7.

Free lesson plan from eurekami.com/lesson-plan-builder

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Colour, prisms and refraction

Name

Date

Score/ 6

  1. Question 1

    Colour and light: which statement is NOT true?

    • A. A red filter lets red light through and absorbs other colours.
    • B. White light is a mixture of colours.
    • C. Black objects absorb most of the light that falls on them.
    • D. A red filter turns white light red by adding red.

  2. Question 2

    What colour does a green leaf look under only red light?

    • A. red
    • B. white
    • C. green
    • D. black (very dark)

  3. Question 3

    What colour does a white T-shirt look under only red light?

    • A. white
    • B. green
    • C. red
    • D. blue

  4. Question 4

    What does a prism do to white light?

    • A. stops it completely
    • B. turns it black
    • C. splits it into a spectrum of colours
    • D. makes it brighter

  5. Question 5

    Why does a red apple look red in white light?

    • A. It reflects red light and absorbs the other colours
    • B. It absorbs red light
    • C. It reflects all colours
    • D. It makes red light

  6. Question 6

    A pencil in a glass of water looks bent. Why?

    • A. Light reflects off the water
    • B. Light refracts (changes direction) as it passes from water to air
    • C. The glass is curved
    • D. The water bends the pencil

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Answer key: Colour, prisms and refraction

  1. 1. D. A red filter turns white light red by adding red.

  2. 2. D. black (very dark)

  3. 3. C. red

  4. 4. C. splits it into a spectrum of colours

  5. 5. A. It reflects red light and absorbs the other colours

  6. 6. B. Light refracts (changes direction) as it passes from water to air