Colour of lightIB MYP Physics: Subtopic test

1. 1
   A student shines a narrow beam of white light through a glass prism in a darkened room. A band of different colours appears on a white screen on the other side of the prism, with red at one end and violet at the other.

   (a)

   What is the name for the splitting of white light into colours by the prism?

   [1 mark]

   • ADispersion
   • BReflection
   • CDiffraction
   • DAbsorption

   (b)

   Which statement about white light is correct?

   [1 mark]

   • AIt is a single colour that the prism changes
   • BIt is a mixture of all the colours of the spectrum
   • CIt contains only the three primary colours of paint
   • DIt becomes coloured because the glass is coloured

   (c)

   Explain why the prism splits the white light into different colours.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A theatre lighting technician is setting up spotlights on a white screen. She has three spotlights that shine pure red, pure green and pure blue light. She also has a magenta filter, which she can place in front of a spotlight that gives white light.

   (a)

   The red and green spotlights overlap on the white screen. What colour does the overlap appear?

   [1 mark]

   • AMagenta
   • BCyan
   • CYellow
   • DWhite

   (b)

   All three spotlights overlap in the same place. What colour does the overlap appear?

   [1 mark]

   • ABlack
   • BGrey
   • CYellow
   • DWhite

   (c)

   Describe what happens to red, green and blue light when white light passes through the magenta filter.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student investigates how objects look under different coloured lights in a dark room. She uses lamps that give pure red, pure green and pure blue light, and three objects: a white sheet of paper, a red apple and a blue book. Under green light, the white sheet looked green and the red apple looked black. Under red light, the white sheet looked red and the blue book looked black.

   (a)

   Identify the independent variable, the dependent variable and one control variable in this investigation.

   [3 marks]

   (b)

   Explain the results. Suggest one improvement to the investigation.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A school theatre uses old filament spotlights with coloured plastic filters, and each filter absorbs most of the light that falls on it. The school is deciding whether to replace them with LED spotlights that mix red, green and blue light electronically to make any colour. The LED set costs about three times as much to buy but uses far less electricity. In one scene an actor wears a yellow shirt.

   (a)

   Explain why a yellow shirt looks yellow in white light, red under a red spotlight and black under a blue spotlight.

   [6 marks]

   (b)

   Discuss and evaluate whether the school should replace the filtered spotlights with LED spotlights.

   [6 marks]

   Total for question 4: 12 marks

End of questions