Primary 3 Science Light Quiz

Primary 3 Science Quiz - Light

Answer Key

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Section A: Multiple Choice Questions (1 mark each)

1. (C) A burning candle

• A burning candle produces its own light and is therefore a source of light.
• The Moon and a mirror only reflect light; a book does not produce or reflect light as a source.
• [1 mark] for correct answer.

2. (C) straight

• Light travels in a straight line. This is a fundamental property of light.
• [1 mark] for correct answer.

3. (D) path

• The bright circle shows the path of light from the torch hitting the wall.
• [1 mark] for correct answer.

4. (B) blocked

• A shadow is formed when an object blocks light from passing through.
• [1 mark] for correct answer.

5. (C) Clear glass

• Clear glass is transparent and allows most light to pass through.
• Wood, metal, and cardboard are opaque and block light.
• [1 mark] for correct answer.

6. (C) produces

• The Sun is a luminous source — it produces (emits) its own light.
• [1 mark] for correct answer.

7. (B) reflection

• A mirror reflects light, producing an image called a reflection.
• [1 mark] for correct answer.

8. (C) A frosted glass window

• Translucent materials allow some (but not all) light to pass through. Frosted glass scatters light.
• A wooden door and metal spoon are opaque; a clear plastic ruler is transparent.
• [1 mark] for correct answer.

9. (B) dark

• A shadow is a dark area where light has been blocked by an object.
• [1 mark] for correct answer.

10. (C) see

• Light enters our eyes and enables us to see objects around us.
• [1 mark] for correct answer.

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Section B: True or False (1 mark each)

11. False

• The Moon does not produce its own light. It reflects light from the Sun.
• [1 mark] for correct answer.

12. True

• Transparent materials (e.g., clear glass, clear water) allow most light to pass through them.
• [1 mark] for correct answer.

13. False

• The size of a shadow depends on the distance between the light source and the object, and between the object and the screen. Shadows can be larger or smaller than the object.
• [1 mark] for correct answer.

14. True

• A mirror has a smooth, shiny surface that reflects light, producing a clear image.
• [1 mark] for correct answer.

15. True

• Opaque materials (e.g., wood, metal, cardboard) do not allow any light to pass through them.
• [1 mark] for correct answer.

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Section C: Short Answer Questions (2 marks each)

16. State two characteristics of a source of light. [2]

• (i) It produces (emits) its own light. [1]
• (ii) It can be seen in the dark / it gives off light. [1]
• Acceptable answers include: produces light, emits light, gives off light, can be seen in darkness, does not need to reflect light from another source.
• [1 mark] for each correct characteristic, [2 marks] total.

17. Draw and label the shadow on the screen. [2]

• The shadow should be drawn as a shaded (dark) region on the screen, directly behind the opaque object relative to the torch. [1]
• The shaded region should be clearly labelled "shadow" or "shadow of object". [1]
• The shadow should be roughly the same shape as the object (or slightly larger, depending on distances).
• Marking note: Award [1] for correct position of shadow (behind object, on screen), [1] for correct shading and labelling.

18. Explain why a shadow is formed when light shines on an opaque object. [2]

• Light travels in a straight line. [1]
• The opaque object blocks the light from passing through, so the area behind the object (where light cannot reach) becomes dark — this dark area is the shadow. [1]
• Acceptable phrasing: "Light travels in straight lines and cannot pass through opaque objects. The area behind the object where light cannot reach is dark and forms a shadow."
• [2 marks] for complete explanation covering both points.

19. Complete the table. [2]

Material	Classification
Clear glass	Transparent
Tissue paper	Translucent
Wooden block	Opaque
Frosted glass	Translucent

• [0.5 mark] for each correct classification, [2 marks] total.
• Common mistake: Students may classify tissue paper as opaque. Accept translucent as correct because some light passes through thin tissue paper.

20. (a) Describe the relationship. [1]

• As the distance of the object from the light source increases, the length/size of the shadow increases. [1]
• Acceptable phrasing: "The further the object is from the torch, the longer the shadow." OR "The shadow gets bigger when the object is placed further from the light source."
• [1 mark] for correct description of the trend.

20. (b) Predict the shadow length at 40 cm. [1]

• The pattern shows: shadow length = distance ÷ 2 (or shadow length increases by 5 cm for every 10 cm increase in distance).
• At 40 cm: shadow length = 40 ÷ 2 = 20 cm. [1]
• Working: 10 cm → 5 cm, 20 cm → 10 cm, 30 cm → 15 cm, so 40 cm → 20 cm.
• [1 mark] for correct answer with or without working shown.

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Total: 40 marks