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Primary 4 Science Light Quiz
Free P4 Science Light quiz, Ox Exam version, with questions, answers, and syllabus-aligned practice for Singapore students.
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Primary 4 Science Quiz - Light: Answer Key
Answer 1.
C — the Moon. Teaching note: A source of light gives out (makes) its own light. The Sun, a firefly and a burning candle all make their own light. The Moon does not make light; it only reflects sunlight, so it is not a source of light. Common mistake: Thinking the Moon glows like a lamp at night. [2 marks]
Answer 2.
B. Method: Ask "Where did the light that reached Mei's eyes come from?"
- The lamp is the source; its light shines on the book.
- The book bounces (reflects) the light into Mei's eyes, so she sees it. Why others are wrong: A — a book is not a light source. C — eyes receive light; they do not send light out. D — if the book absorbed all the light, no light would reach her eyes and she would see nothing. [2 marks]
Answer 3.
C — straight lines. This is a key property of light. It explains why shadows have clear outlines and why light cannot bend around an object to reach behind it. [2 marks]
Answer 4.
D — a mirror. To form a shadow, three things are needed: a source of light, an object to block the light, and a surface (screen/wall) for the shadow to fall on. A mirror is not needed at all. [2 marks]
Answer 5.
B — it becomes bigger. Reasoning: Light spreads out from the torch. When the torch is closer to the robot, the robot blocks more of the spreading light, so its shadow on the screen grows larger. The screen did not move, so the change is caused only by the torch moving closer. [2 marks]
Answer 6.
(a) Any one natural source: the Sun (also accept: firefly, stars, lightning). (b) Any one man-made source: torch (also accept: lamp, candle, television screen). Marking: 1 mark each. The examples must truly give out their own light. Common mistake: Writing "Moon" as a source — the Moon only reflects light. [2 marks]
Answer 7.
(i) straight; (ii) shadow. Explanation: Light travels in straight lines. When an object blocks the light completely, no light reaches that part of the surface behind it, so a dark shadow is formed there. [2 marks]
Answer 8.
The Moon reflects light from the Sun into Ravi's eyes, so he is able to see it. Marking breakdown:
- 1 mark: states the Moon reflects sunlight (light from the Sun).
- 1 mark: states the reflected light enters/reaches Ravi's eyes. Common mistake: Saying the Moon gives out its own light — this contradicts the question. [2 marks]
Answer 9.
With the lights off and curtains closed, no light can enter the room, so no light can reflect off the pencil into Wei Ming's eyes. We can only see objects when light from them enters our eyes, so in total darkness nothing can be seen. [2 marks]
Answer 10.
Region X is a shadow. Explanation: The torch gives out light that travels in straight lines. The wooden block blocks the light, so light cannot reach the part of the screen directly behind the block. That dark region, X, is the shadow. Marking breakdown:
- 1 mark: names X as a shadow.
- 1 mark: explains the block stops/blocks the straight-line light from reaching the screen. Expected visual support: torch on the left, straight parallel rays, block stopping the rays, dark rectangle X on the screen behind the block. [2 marks]
Answer 11.
(a) lit matchstick — gives out its own light (a flame is a source of light). (b) mirror — reflects light (a mirror sends light back but makes none of its own). Marking: 1 mark each. [2 marks]
Answer 12.
The shadow is square. Explanation: The card faces the screen flat, and light travels in straight lines, so the shadow keeps the same outline as the card. The shadow shape follows the shape of the object. Common mistake: Saying the shadow is round or larger — with the card flat and facing the screen, the outline stays square. [2 marks]
Answer 13.
She must keep the distance between the toy and the screen the same (also accept: use the same torch/brightness, or the same toy). Reasoning: For a fair test, only one variable — the torch-toy distance — may change. All other conditions must stay the same so any change in shadow size is due only to the changed variable. [2 marks]
Answer 14.
The shadow becomes smaller. Explanation: As the light source moves further from the object, the object blocks less of the spreading light, so the shadow formed on the screen shrinks. This is the opposite of Question 5. [2 marks]
Answer 15.
The shadow is formed on the west side (the side away from the Sun). Explanation: The Sun is in the east, and its light travels in straight lines towards the tree. The tree blocks the light, so the shadow forms on the opposite side of the tree — the west. Marking breakdown:
- 1 mark: correct side (west/opposite the Sun).
- 1 mark: explanation using light travelling in straight lines and being blocked by the tree. [2 marks]
Answer 16.
(a) Circle (round) — the shadow matches the circular card in Set-up B. [1 mark]
(b) Conclusion: **The
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Primary 4 Science Quiz - Light: Answer Key
Answer 1.
C — the Moon. Teaching note: A source of light gives out (makes) its own light. The Sun, a firefly and a burning candle all make their own light. The Moon does not make light; it only reflects sunlight, so it is not a source of light. Common mistake: Thinking the Moon glows like a lamp at night. [2 marks]
Answer 2.
B. Method: Ask "Where did the light that reached Mei's eyes come from?"
- The lamp is the source; its light shines on the book.
- The book bounces (reflects) the light into Mei's eyes, so she sees it. Why others are wrong: A — a book is not a light source. C — eyes receive light; they do not send light out. D — if the book absorbed all the light, no light would reach her eyes and she would see nothing. [2 marks]
Answer 3.
C — straight lines. This is a key property of light. It explains why shadows have clear outlines and why light cannot bend around an object to reach behind it. [2 marks]
Answer 4.
D — a mirror. To form a shadow, three things are needed: a source of light, an object to block the light, and a surface (screen/wall) for the shadow to fall on. A mirror is not needed at all. [2 marks]
Answer 5.
B — it becomes bigger. Reasoning: Light spreads out from the torch. When the torch is closer to the robot, the robot blocks more of the spreading light, so its shadow on the screen grows larger. The screen did not move, so the change is caused only by the torch moving closer. [2 marks]
Answer 6.
(a) Any one natural source: the Sun (also accept: firefly, stars, lightning). (b) Any one man-made source: torch (also accept: lamp, candle, television screen). Marking: 1 mark each. The examples must truly give out their own light. Common mistake: Writing "Moon" as a source — the Moon only reflects light. [2 marks]
Answer 7.
(i) straight; (ii) shadow. Explanation: Light travels in straight lines. When an object blocks the light completely, no light reaches that part of the surface behind it, so a dark shadow is formed there. [2 marks]
Answer 8.
The Moon reflects light from the Sun into Ravi's eyes, so he is able to see it. Marking breakdown:
- 1 mark: states the Moon reflects sunlight (light from the Sun).
- 1 mark: states the reflected light enters/reaches Ravi's eyes. Common mistake: Saying the Moon gives out its own light — this contradicts the question. [2 marks]
Answer 9.
With the lights off and curtains closed, no light can enter the room, so no light can reflect off the pencil into Wei Ming's eyes. We can only see objects when light from them enters our eyes, so in total darkness nothing can be seen. [2 marks]
Answer 10.
Region X is a shadow. Explanation: The torch gives out light that travels in straight lines. The wooden block blocks the light, so light cannot reach the part of the screen directly behind the block. That dark region, X, is the shadow. Marking breakdown:
- 1 mark: names X as a shadow.
- 1 mark: explains the block stops/blocks the straight-line light from reaching the screen. Expected visual support: torch on the left, straight parallel rays, block stopping the rays, dark rectangle X on the screen behind the block. [2 marks]
Answer 11.
(a) lit matchstick — gives out its own light (a flame is a source of light). (b) mirror — reflects light (a mirror sends light back but makes none of its own). Marking: 1 mark each. [2 marks]
Answer 12.
The shadow is square. Explanation: The card faces the screen flat, and light travels in straight lines, so the shadow keeps the same outline as the card. The shadow shape follows the shape of the object. Common mistake: Saying the shadow is round or larger — with the card flat and facing the screen, the outline stays square. [2 marks]
Answer 13.
She must keep the distance between the toy and the screen the same (also accept: use the same torch/brightness, or the same toy). Reasoning: For a fair test, only one variable — the torch-toy distance — may change. All other conditions must stay the same so any change in shadow size is due only to the changed variable. [2 marks]
Answer 14.
The shadow becomes smaller. Explanation: As the light source moves further from the object, the object blocks less of the spreading light, so the shadow formed on the screen shrinks. This is the opposite of Question 5. [2 marks]
Answer 15.
The shadow is formed on the west side (the side away from the Sun). Explanation: The Sun is in the east, and its light travels in straight lines towards the tree. The tree blocks the light, so the shadow forms on the opposite side of the tree — the west. Marking breakdown:
- 1 mark: correct side (west/opposite the Sun).
- 1 mark: explanation using light travelling in straight lines and being blocked by the tree. [2 marks]
Answer 16.
(a) Circle (round) — the shadow matches the circular card in Set-up B. [1 mark]
(b) Conclusion: The shape of the shadow follows the shape of the object that blocks the light. Reasoning: All three set-ups kept the distances and torch the same; only the card shape changed. Each set-up produced a shadow shaped like its card (star, circle, triangle), so the card's shape determines the shadow's shape. Marking breakdown:
- 1 mark: states shadow shape matches/follows object shape.
- 1 mark: links this to the fair comparison across the three set-ups. [2 marks] [Total: 3 marks]
Answer 17.
(a) As the torch is moved further from the box, the size of the shadow becomes smaller. [1 mark]
(b) Prediction: the shadow will be very small (smaller than at 20 cm). Reason: The table shows a clear pattern — each time the distance increases by 5 cm, the shadow gets smaller. Following this pattern, at 25 cm the shadow should continue to shrink. Marking breakdown:
- 1 mark: correct prediction following the pattern.
- 1 mark: reason based on the trend in the results. [2 marks] [Total: 3 marks]
Answer 18.
Siti is correct. Explanation: Our eyes do not give out light — they can only receive light that enters them. We see objects when light shines on them and reflects off them into our eyes. In a dark storeroom there is no light source, so no light can reflect off the chairs into Ben's eyes, and the chairs cannot be seen. Marking breakdown:
- 1 mark: identifies Siti as correct.
- 1 mark: states eyes do not give out light / we see by reflected light entering our eyes.
- 1 mark: applies this to the dark storeroom — no light means nothing can be seen. [3 marks]
Answer 19.
Amir can carry out a fair test like this:
- Change: the distance between the object and the screen (move the screen to different positions, or move the object).
- Keep the same: the same torch, the same distance between the torch and the object, and the same object.
- Measure: the size of the shadow formed on the screen each time. Reasoning: Only one variable may change at a time; everything else must stay the same so any change in shadow size is caused only by the changed distance. Marking breakdown:
- 1 mark: correct variable to change.
- 1 mark: correct variables to keep the same.
- 1 mark: correct thing to measure (shadow size). [3 marks]
Answer 20.
(a) The lamp gives out light that travels in straight lines towards the puppet. The puppet blocks the light, so light cannot reach the part of the screen directly behind it. That dark area on the screen is the puppet's shadow. Marking breakdown:
- 1 mark: light travels in straight lines from the lamp and is blocked by the puppet.
- 1 mark: no light reaches that part of the screen, forming the dark shadow. [2 marks]
(b) The shadow becomes bigger. Reason: With the puppet closer to the lamp, it blocks more of the spreading light, so its shadow on the screen grows larger. [1 mark] [Total: 3 marks]
— End of Answer Key —