Primary 5 Science Light Quiz

Primary 5 Science Quiz - Light

Answer Key

Section A: Multiple Choice (1 mark each)

1. (C) straight
Explanation: Light travels in a straight line. This is a fundamental property of light and can be demonstrated using the pinhole camera experiment.

2. (C) The Sun
Explanation: The Sun produces its own light and is therefore a natural source of light. The Moon only reflects sunlight and does not produce its own light. A torch and a light bulb are artificial/man-made sources.

3. (B) reflected
Explanation: When light hits a smooth, shiny surface (such as a mirror), it bounces back. This is called reflection.

4. (B) travels in a straight line and cannot pass through opaque objects
Explanation: Because light travels in a straight line, it cannot bend around opaque objects. The region behind the opaque object where light cannot reach forms a shadow.

5. (C) Clear glass
Explanation: Clear glass is transparent and allows most light to pass through. Wood, metal, and cardboard are opaque and block light.

6. (B) inverted and real
Explanation: In a pinhole camera, light from the top of the object passes through the pinhole and reaches the bottom of the screen, and vice versa. This produces an inverted (upside-down) real image.

7. (C) A book
Explanation: A book is opaque — it does not allow light to pass through. Clear plastic is transparent, frosted glass is translucent, and water is transparent.

8. (C) dispersion
Explanation: Dispersion is the splitting of white light into its component colours (red, orange, yellow, green, blue, indigo, violet) when it passes through a prism.

9. (B) reflects
Explanation: The colour of an opaque object is determined by the colour of light it reflects. For example, a red apple reflects red light and absorbs all other colours.

10. (C) refracted and reflected
Explanation: A rainbow is formed when sunlight enters water droplets, is refracted (bent), reflected off the inner surface of the droplet, and refracted again as it exits, separating into different colours.

Section B: Short Answer

11. [2 marks]
Two properties of light (any two of the following, 1 mark each):

• Light travels in a straight line.
• Light can be reflected.
• Light can be refracted.
• Light travels at high speed.
• Light enables us to see objects.
• Light can be absorbed by objects.

Marking note: Award 1 mark for each correct property, up to a maximum of 2 marks. Vague answers such as "light is bright" are not accepted.

12. [3 marks]

Marking note: 1 mark for each correct classification.

13. (a) [1 mark]
The ray approaching the mirror is the incident ray. The ray bouncing off the mirror is the reflected ray. Both must be correctly labelled on the diagram.

Marking note: Award 1 mark if both rays are correctly identified. No mark if only one is correct.

(b) [1 mark]
The angle of incidence is equal to the angle of reflection.
(Or: angle of incidence = angle of reflection)

14. [2 marks]
In the early morning and late afternoon, the Sun is low in the sky, so light hits the object at a shallow angle, producing a long shadow. [1 mark] At noon, the Sun is high in the sky (almost directly overhead), so light hits the object from above, producing a short shadow. [1 mark]

Marking note: Award 1 mark for each correct explanation. The answer must refer to the position/angle of the Sun and the resulting shadow length.

15. (a) [1 mark]
Refraction (of light).

(b) [2 marks]
Light travels at different speeds in air and water. [1 mark] When light passes from water to air, it bends at the surface, causing the pencil to appear bent or displaced. [1 mark]

Marking note: Award 1 mark for mentioning different speeds in different media, and 1 mark for explaining the bending/displacement effect. Simply saying "light bends" without explanation earns only 1 mark.

16. [2 marks]
A transparent material allows most light to pass through, so objects can be seen clearly through it. [1 mark] A translucent material allows only some light to pass through, so objects appear blurry or cannot be seen clearly through it. [1 mark]

Marking note: The key distinction is clarity of vision through the material. Answers that only state "transparent lets light through, translucent lets some light through" without mentioning visibility earn 1 mark only.

Section C: Application & Reasoning

17. (a) [2 marks]
Priya will observe an inverted (upside-down) image of the candle flame on the screen. [1 mark] The image will be real and upside down. [1 mark]

Alternative: A drawing showing an inverted candle flame on the screen is also acceptable for full marks.

(b) [1 mark]
This experiment proves that light travels in a straight line.

18. (a) [2 marks]
The light path should show:

• Light from the object strikes Mirror 1 (top mirror) and reflects downward. [1 mark]
• The reflected light then strikes Mirror 2 (bottom mirror) and reflects into the eye. [1 mark]

Drawing note: The path should form a "Z" or stepped pattern with arrows indicating direction. Both reflection points must be shown with correct angles.

(b) [1 mark]
One real-life use of a periscope:

• Used in submarines to see above the water surface.
• Used in trenches during warfare to observe without exposing oneself.
• Used in some buildings/vehicles to see over obstacles.

Marking note: Any valid real-life application earns 1 mark.

19. (a) [1 mark]
The shirt will appear black (or very dark).

(b) [2 marks]
A red shirt reflects red light and absorbs all other colours. [1 mark] Under blue light, there is no red light to reflect, so the shirt absorbs the blue light and reflects almost no light, making it appear black. [1 mark]

Marking note: Award 1 mark for stating that the shirt absorbs blue light, and 1 mark for explaining that no red light is available to reflect. Simply saying "it absorbs the light" without mentioning the colour-specific reflection earns only 1 mark.

20. (a) [1 mark]
Dispersion (of light).

(b) [3 marks]

• Sunlight (white light) enters the raindrop and is refracted (bent). [1 mark]
• Different colours of light are refracted by different amounts — red light bends the least and violet bends the most. [1 mark]
• The light is also reflected inside the raindrop and refracted again as it exits, causing the colours to spread out and form a rainbow. [1 mark]

Marking note: Award 1 mark for mentioning refraction upon entry, 1 mark for explaining that different colours bend by different amounts, and 1 mark for mentioning internal reflection and/or the final separation of colours. Answers that only say "light is split into colours" without explaining the mechanism earn a maximum of 1 mark.

End of Answer Key