Sec 2 Science — Colours Worksheet

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Instructions: Answer all questions. For MCQ, shade the correct option. For OEQ, show all working and explain your reasoning clearly. Diagrams are NOT to scale unless stated otherwise.

Key Concepts — Colours of Light

White light is a mixture of seven colours: red, orange, yellow, green, blue, indigo, violet (ROYGBIV).
Primary colours of light: Red, Green, Blue (RGB) — additive mixing.
Secondary colours of light: Yellow (R+G), Cyan (B+G), Magenta (R+B).
An object appears a certain colour because it reflects that colour and absorbs others.
A black object absorbs all colours; a white object reflects all colours.

SECTION A

Multiple Choice Questions

[12 marks]

Question 1

Which of the following best describes what happens when white light passes through a glass prism?

A The light is reflected back entirely.
B The light is split into its component colours due to dispersion.
C The light becomes completely white again after refraction.
D Only the red colour passes through the prism.

Question 2

Which colour of visible light travels the fastest in glass?

A Violet
B Blue
C Red
D Green

Question 3

Which two colours of light must be mixed to produce yellow light?

A Red and Blue
B Green and Blue
C Red and Green
D Yellow and White

Question 4

A red apple is viewed under green light. What colour does the apple appear?

A Red
B Green
C Yellow
D Black

Question 5

Which colour of light is refracted the most when white light passes through a prism?

A Red
B Orange
C Green
D Violet

Question 6

What colour is produced when all three primary colours of light (red, green, blue) are mixed together?

A Magenta
B Cyan
C Yellow
D White

Question 7

A piece of cyan paper is viewed under red light. What colour does the paper appear?

A Cyan
B Red
C Blue
D Black

Question 8

Which statement about the colours in the visible spectrum is correct?

A Red light has the shortest wavelength and travels fastest in glass.
B Violet light has the longest wavelength and travels slowest in glass.
C Red light has the longest wavelength and travels fastest in glass.
D All colours of light travel at the same speed in glass.

Question 9

A stage is lit with blue light. A performer wears a yellow costume. What colour does the costume appear under the blue light?

A Yellow
B Blue
C Green
D Black

Question 10

Which secondary colour of light is produced by mixing red and blue light?

A Cyan
B Magenta
C Yellow
D White

Question 11

A white sheet of paper is illuminated with red light. What colour does the paper appear?

A White
B Red
C Black
D Magenta

Question 12

Which colour of light is refracted the least when white light passes through a prism?

A Violet
B Blue
C Green
D Red

SECTION B

Open Ended Questions

[38 marks]

Question 13 [6 marks]

(a) Define the term dispersion of white light. [2]

(b) A beam of white light passes through a glass prism and produces a spectrum on a screen. The colours observed are labelled A to G from top to bottom.

(i) Name the colour at position A. [1]

(ii) Name the colour at position G. [1]

(iii) Which colour, A or G, travels the fastest in glass? Explain your answer. [2]

Question 14 [8 marks]

(a) State the three primary colours of light. [3]

(b) For each pair below, state the secondary colour of light produced when they are mixed:

(i) Red + Green = [1]

(ii) Blue + Green = [1]

(iii) Red + Blue = [1]

(c) What colour is produced when all three primary colours of light are mixed together? [1]

Question 15 [8 marks]

A white T-shirt, a red apple, and a black jacket are placed under white light in a dark room.

(a) Explain why the white T-shirt appears white. [2]

(b) Explain why the red apple appears red. [2]

(c) Explain why the black jacket appears black. [2]

(d) Now the room is lit only with blue light. What colour does each item appear? Explain your answer for the red apple. [2]

Question 16 [8 marks]

(a) A magenta filter is placed in front of a white light source. Describe what happens to the light that passes through the filter and explain why. [3]

(b) A cyan filter is placed in front of a white light source. This filtered light then shines onto a red apple. What colour does the apple appear? Explain your answer fully. [5]

Question 17 [8 marks]

(a) A beam of white light passes through a glass prism. The spectrum produced is shown on a screen.

(i) Which colour in the spectrum has the longest wavelength? [1]

(ii) Which colour in the spectrum has the shortest wavelength? [1]

(iii) If the prism is replaced with a glass block of the same material but different shape, will dispersion still occur? Explain. [2]

(b) A student places a red filter between the prism and the screen. Describe what is observed on the screen and explain why. [4]

Answer Key

Section A — Multiple Choice [12 marks]

Q1: B — The light is split into its component colours due to dispersion. [1]

Q2: C — Red travels the fastest in glass. [1]

Q3: C — Red + Green = Yellow (additive mixing). [1]

Q4: D — A red apple absorbs green light and reflects red. Under green light, no red is available to reflect → appears black. [1]

Q5: D — Violet is refracted the most (shortest wavelength). [1]

Q6: D — R + G + B = White. [1]

Q7: D — Cyan reflects blue and green, absorbs red. Under red light, no blue or green available → appears black. [1]

Q8: C — Red has the longest wavelength and travels fastest in glass. [1]

Q9: D — Yellow costume reflects red + green. Under blue light, neither is available → absorbs all → appears black. [1]

Q10: B — Red + Blue = Magenta (additive mixing). [1]

Q11: B — White reflects all colours, so under red light it appears red. [1]

Q12: D — Red is refracted the least (longest wavelength). [1]

Section B — Open Ended

Question 13 [6 marks]

(a) Dispersion is the splitting of white light into its component colours (red, orange, yellow, green, blue, indigo, violet) when it passes through a prism due to different wavelengths being refracted by different amounts. [M1: splitting, A1: component colours / different refraction] [2]

(b)(i) Red (position A — least refracted). [1]

(b)(ii) Violet (position G — most refracted). [1]

(b)(iii) A (red) travels fastest. Red has the longest wavelength and is refracted the least, meaning it travels faster through glass than violet which has a shorter wavelength and is refracted more. [M1: identifies red/A, A1: explains with wavelength/refraction relationship] [2]

Question 14 [8 marks]

(a) Red, Green, Blue (one mark each). [3]

(b)(i) Yellow. [1]

(b)(ii) Cyan. [1]

(b)(iii) Magenta. [1]

(c) White (R + G + B = white light). [1]

Question 15 [8 marks]

(a) A white T-shirt reflects all colours of the visible spectrum. Under white light, all colours are reflected into our eyes, so it appears white. [2]

(b) A red apple absorbs all colours except red. Under white light, the red component is reflected while other colours (orange, yellow, green, blue, indigo, violet) are absorbed. Only red reaches our eyes, so it appears red. [2]

(c) A black jacket absorbs all colours of the visible spectrum and reflects none. Since no light is reflected into our eyes, it appears black. [2]

(d) White T-shirt → white (reflects blue). Red apple → black (absorbs blue, has no red to reflect). Black jacket → black (absorbs all light including blue).
Explanation for apple: The red apple only reflects red light. Under blue light, there is no red component available to be reflected, so the apple absorbs the blue light and appears black. [1 for colours + 1 for explanation] [2]

Question 16 [8 marks]

(a) Only red and blue light pass through the magenta filter, producing magenta light. The filter absorbs green light because a magenta filter transmits only its constituent colours — red and blue (the two primary colours that make magenta). [M1: identifies R+B pass through, A1: G absorbed, A1: explains magenta = R+B] [3]

(b) The apple appears black. [1]
Explanation:
• Cyan light is made of blue + green (no red). [M1]
• A red apple only reflects red light and absorbs all other colours. [A1]
• Since the cyan light contains no red component, the apple has nothing to reflect. [A1]
• The apple absorbs both the blue and green components of the cyan light. [A1]
• With no light reflected, the apple appears black. [A1] [5]

Question 17 [8 marks]

(a)(i) Red (longest wavelength in visible spectrum). [1]

(a)(ii) Violet (shortest wavelength in visible spectrum). [1]

(a)(iii) Yes, dispersion will still occur as long as the glass block has a shape that causes refraction at an angle (non-parallel surfaces), because different wavelengths are refracted by different amounts regardless of shape. [M1: yes + A1: reason] [2]

(b) Only red light appears on the screen (a red band).
Explanation:
• The spectrum contains all seven colours from the prism. [A1]
• A red filter only transmits red light and absorbs all other colours (orange, yellow, green, blue, indigo, violet). [M1: identifies transmission + absorption]
• Therefore, only the red component of the spectrum passes through the filter. [A1]
• The rest of the screen appears dark/black where no light reaches. [A1] [4]