Primary 4 Science Light Quiz

Primary 4 Science Quiz - Light

Answer Key

Total Marks: 40

Section A: Multiple Choice Questions (10 marks)

1. (C) straight

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

2. (C) The Sun

• The Sun produces its own light and is a natural source of light.
• A torch and light bulb are man-made sources. The Moon does not produce its own light; it reflects sunlight.
• [1 mark] for correct answer.

3. (B) shadow

• When an opaque object blocks light, a shadow is formed on the opposite side of the light source.
• [1 mark] for correct answer.

4. (B) near to

• When the object is closer to the light source, it blocks more of the spreading light rays, producing a larger and darker shadow. The darkest shadow occurs when the object is nearest to the light source because the greatest concentration of light is blocked.
• [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. (B) bigger

• When the object moves closer to the light source, the light rays spread out more behind the object, making the shadow larger.
• [1 mark] for correct answer.

7. (C) opaque

• Opaque objects do not allow light to pass through them. Transparent objects allow all light through; translucent objects allow some light through.
• [1 mark] for correct answer.

8. (B) reflection

• A mirror reflects light, producing an image of the object in front of it. This is called a reflection.
• [1 mark] for correct answer.

9. (C) A shiny spoon

• A shiny spoon reflects light but does not produce its own light, so it is not a source of light. Fireflies, candles, and oil lamps all produce their own light.
• [1 mark] for correct answer.

10. (C) allows some light to pass through

• A translucent object allows some (but not all) light to pass through. Examples include frosted glass and tissue paper.
• [1 mark] for correct answer.

Section B: Short Answer Questions (20 marks)

11. [2 marks]

• (a) Light travels in a straight line. [1]
• (b) Light cannot pass through opaque objects. [1]
• Acceptable alternatives for (b): Light can be reflected / Light enables us to see objects / Light travels very fast.
• Award 1 mark each for any two correct properties of light.

12. [3 marks]

• Shape of shadow: Rectangular / book-shaped (same outline as the book). [1]
• Explanation: Light travels in straight lines from the torch. The book is opaque and blocks the light. The area behind the book where light cannot reach forms a shadow that has the same shape as the book. [1]
• Marking note: The drawing should show a dark rectangular shape on the screen. Award [1] for a reasonable shadow shape drawn on the screen area.

13. [3 marks]

• Clear plastic sheet: Transparent [1]
• Frosted glass: Translucent [1]
• Wooden door: Opaque [1]
• Award 1 mark each for correct classification.

14. [3 marks]

• (a) 12 noon [1]
• (b) At 12 noon, the Sun is higher in the sky (closer to directly overhead). When the Sun is higher, the light rays hit the stick at a steeper angle, so the shadow cast is shorter. At 9 a.m., the Sun is lower in the sky, so the shadow is longer. [1]
• Marking note: Award [1] for mentioning that the Sun's position in the sky affects shadow length, and [1] for the correct comparison.

15. [2 marks]

• We see objects when light reflects off them and enters our eyes. In a completely dark room, there is no light. Without light, there is no light reflecting off the objects, so our eyes cannot detect them. Therefore, we cannot see the objects. [2]
• Marking note: Award [1] for mentioning that there is no light in a dark room. Award [1] for linking this to the inability to see (no light reflects into our eyes).

16. [3 marks]

• (a) The shadow becomes shorter when the Sun is higher in the sky. [1]
• (b) Early morning or late evening / sunrise or sunset. [1]
• Marking note: Accept "early morning" or "late evening" or equivalent. Award [1] for correct time of day.

Section C: Structured / Application Questions (10 marks)

17. [3 marks]

• (a) The shadow became bigger / larger. [1]
• (b) Light travels in straight lines from the torch. When the torch is moved closer to the figure, the light rays spread out more behind the figure before reaching the screen. This means a larger area of the screen is blocked from light, so the shadow increases in size. [2]
• Marking note: Award [1] for stating that light travels in straight lines. Award [1] for explaining that moving the torch closer causes the shadow to become larger.

18. [3 marks]

• (a) Aluminium foil is opaque because no light was detected on the screen. This means it blocked all the light from the torch. [1]
• (b) Tissue paper (or thin cloth) is translucent because only dim / slightly dim light was detected on the screen, meaning some light passed through but not all. [1]
• Marking note: Accept either tissue paper or thin cloth as the translucent material. Award [1] for correct identification with a valid explanation.
• (c) Example: A lampshade is made of translucent material. It allows some light to pass through to light up the room but reduces the glare from the bulb, making the light softer and more comfortable for the eyes. [1]
• Marking note: Accept any reasonable real-life use (e.g., bathroom windows, curtains, shades). Award [1] for a suitable use with a correct explanation.

19. [3 marks]

• (a) Light from the lamp travels in straight lines towards the wall. Amir's body is opaque and blocks the light. The area on the wall behind Amir where light cannot reach forms a shadow. [2]
• Marking note: Award [1] for mentioning that light is blocked by Amir. Award [1] for stating that the shadow forms where light cannot reach the wall.
• (b) The shadow on the wall became bigger / larger. [1]
• Explanation: As Amir moves closer to the lamp, he blocks more of the spreading light rays, so the shadow projected onto the wall behind him becomes larger.

20. [2 marks]

• Light from the Sun travels in straight lines. During a solar eclipse, the Moon moves between the Earth and the Sun. The Moon is opaque and blocks the light from the Sun. People on Earth who are in the area where the Moon's shadow falls cannot see the Sun clearly because the light from the Sun is blocked by the Moon. [2]
• Marking note: Award [1] for stating that the Moon blocks the Sun's light. Award [1] for linking this to the formation of a shadow on Earth (people cannot see the Sun). Answers should demonstrate understanding that light travels in straight lines and the Moon casts a shadow on Earth.

End of Answer Key