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Primary 6 PSLE Science Light Quiz
Free P6 PSLE Science Light quiz, Nemo3 Exam version, with questions, answers, and PSLE-focused practice for Singapore students.
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Primary 6 PSLE Science Quiz - Light (Answer Key)
Total Marks: 44
Section A: Multiple-Choice Questions (10 × 2 marks = 20 marks)
1. Answer: (2) Lightning [2]
Explanation: Lightning is a natural source of light produced by electrical discharge in the atmosphere. Candle flame, torchlight, and television screen are man-made (artificial) light sources.
2. Answer: (3) straight line [2]
Explanation: Light travels in straight lines. This is a fundamental property of light called rectilinear propagation. It explains why shadows are formed and why we cannot see around corners.
3. Answer: (3) opaque [2]
Explanation: An opaque object does not allow any light to pass through it. When light hits an opaque object, a dark shadow is formed because light is completely blocked. Transparent objects allow most light through (no shadow), and translucent objects allow some light through (faint shadow).
4. Answer: (3) Black velvet cloth [2]
Explanation: Black velvet cloth has a rough, dark surface that absorbs most light falling on it, reflecting very little. Plane mirrors, polished metal, and still water have smooth, shiny surfaces that reflect light well (regular reflection).
5. Answer: (1) 30° [2]
Explanation: According to the Law of Reflection, the angle of incidence equals the angle of reflection, both measured from the normal. Since the angle of incidence is 30°, the angle of reflection is also 30°.
6. Answer: (3) dispersion [2]
Explanation: Dispersion is the splitting of white light into its constituent colours (spectrum) when it passes through a prism. This happens because different colours of light travel at different speeds in glass and are refracted (bent) by different amounts.
7. Answer: (1) reflects red light and absorbs other colours [2]
Explanation: The colour of an opaque object is the colour of light it reflects. A red apple reflects red light into our eyes and absorbs the other colours (orange, yellow, green, blue, indigo, violet) in white light.
8. Answer: (4) The closer the object is to the light source, the larger the shadow. [2]
Explanation: When an object is closer to a point light source, it blocks a larger angle of light rays, casting a larger shadow on the screen. As the object moves away, the shadow becomes smaller. Shadows form on the side opposite the light source, not facing it.
9. Answer: (3) vacuum, air, and water [2]
Explanation: Light is an electromagnetic wave and does not require a medium. It can travel through vacuum (e.g., sunlight reaching Earth), air, water, glass, and other transparent media. It travels fastest in vacuum and slows down in denser media.
10. Answer: (2) light changes direction when it passes from water to air [2]
Explanation: This is refraction. Light bends when it passes from one medium to another of different optical density (water to air). The light rays from the submerged part of the pencil bend away from the normal as they exit the water, making the pencil appear bent at the surface.
Section B: Structured Questions (5 × 2 marks = 10 marks)
11. [2 marks – ½ mark each correct classification]
| Object | Classification |
|---|---|
| Sun | Light Source |
| Moon | Non-Light Source |
| Firefly | Light Source |
| Mirror | Non-Light Source |
| Lighted candle | Light Source |
| Book | Non-Light Source |
Explanation: Light sources emit their own light. The Sun (nuclear fusion), firefly (bioluminescence), and lighted candle (combustion) produce light. The Moon only reflects sunlight, a mirror reflects light, and a book reflects ambient light – none produce their own light.
12. [2 marks]
Expected diagram features (1 mark each):
- Incident ray from object to mirror, reflected ray from mirror to eye, obeying Law of Reflection (angle i = angle r)
- Virtual image drawn behind the mirror (dashed line), same distance behind mirror as object is in front, same size as object
Explanation: To see an object in a plane mirror, light from the object reflects off the mirror into the eye. The brain traces the reflected rays back in straight lines behind the mirror, forming a virtual image. The image is upright, same size, laterally inverted, and located as far behind the mirror as the object is in front.
13. [2 marks – 1 mark each difference]
Difference 1: A shadow is a dark area formed when an opaque object blocks light; a reflection is an image formed when light bounces off a smooth surface.
Difference 2: A shadow is always dark (same shape as object, no colour/detail); a reflection shows the colours and details of the object.
Other acceptable differences: Shadows form on a screen/surface; reflections appear on/in the reflecting surface. Shadows require an opaque object and a light source; reflections require a smooth, shiny surface and light.
14. [2 marks]
(a) Dispersion [1]
(b) Violet [1]
Explanation: (a) The splitting of white light into its component colours by a prism is called dispersion. (b) Violet light has the shortest wavelength and slows down the most in glass, so it is refracted (bent) the most. Red light has the longest wavelength and is deviated the least.
15. [2 marks]
Answer: The green leaf reflects green light into our eyes and absorbs the other colours (red, orange, yellow, blue, indigo, violet) present in white light from the torch.
Explanation: Under white light, an object's colour is determined by which colour(s) it reflects. A green leaf contains chlorophyll which absorbs red and blue light for photosynthesis and reflects green light.
Section C: Open-Ended Questions (14 marks)
16. [3 marks]
(a) As the distance between the torch and the object increases, the height of the shadow decreases. [1]
(b) When the torch is closer to the object, the light rays spread out more (diverge more) by the time they reach the object, so the object blocks a wider beam of light, casting a larger shadow on the screen. When the torch is further away, the light rays are more parallel, so the object blocks a narrower beam, forming a smaller shadow. [2]
Key concept: Light from a point source diverges. Closer object → larger angular size → larger shadow.
17. [3 marks]
(a) The speed of light decreases (slows down) when it enters the glass block from air. [1]
(b) Light travels slower in glass (optically denser medium) than in air (optically less dense medium). When light enters a denser medium at an angle, it bends towards the normal. [1]
(c) Lateral displacement [1]
Explanation: (a) Light slows down in optically denser media. (b) Refraction towards the normal occurs when light enters a denser medium due to change in speed. (c) The sideways shift of the emergent ray relative to the incident ray is called lateral displacement. The emergent ray is parallel to the incident ray because the two surfaces of the rectangular block are parallel.
18. [4 marks – 1 mark each cell]
| Filter colour | Colour of ball observed | Explanation |
|---|---|---|
| Red | Red | Red filter transmits red light; red ball reflects red light → red light reaches eye |
| Green | Black / Dark | Green filter transmits only green light; red ball absorbs green light → no light reflected to eye |
| Blue | Black / Dark | Blue filter transmits only blue light; red ball absorbs blue light → no light reflected to eye |
Explanation: A coloured filter only allows its own colour to pass through. A red ball reflects only red light. Under red light, it reflects red → appears red. Under green or blue light, it absorbs that light (no red light to reflect) → appears black/dark.
19. [4 marks]
(a) Ray diagram showing: [2]
- Ray from tree → top mirror (45°) → reflects down tube → bottom mirror (45°) → reflects horizontally to eye
- Angles of incidence = angles of reflection = 45° at both mirrors
- Arrows showing direction from object to eye
(b) The image is upright / same size as object / laterally inverted / virtual. (Any one) [1]
(c) The image will not be visible / the light will not reach the eye / the ray will miss the bottom mirror. [1]
Explanation: (a) Periscope works by two reflections at 45° mirrors, turning light 90° each time (total 180°). (b) Plane mirror images are upright, same size, laterally inverted, virtual. (c) If the top mirror is not at 45°, the reflected ray will not hit the bottom mirror at the correct angle to direct light to the eye.
20. [4 marks]
(a) Cardboard [1]
(b) Clear glass → Frosted glass → Tracing paper [1]
(c) Material: Frosted glass (or tracing paper). Explanation: It is translucent – it allows some light to pass through (so the room is lit) but scatters the light, hiding the bright bulb and reducing glare. [2]
Explanation: (a) Cardboard allows 0 lux – completely opaque. (b) Higher light intensity = more transparent. Clear glass (950) > Frosted glass (420) > Tracing paper (380). (c) A lampshade needs to transmit light but diffuse it. Frosted glass or tracing paper are translucent – they transmit light but scatter it, hiding the bulb. Clear glass would show the bulb; cardboard would block all light.
Marking Notes:
- For Section A: 2 marks per correct answer, 0 for incorrect.
- For Section B/C: Award marks for key concepts/keywords as indicated. Accept equivalent phrasing.
- Diagrams: Award marks for correct ray paths, arrows, labels, and image positions.
- Common mistakes: Confusing reflection/refraction, thinking Moon is a light source, thinking shadows form on the light-facing side, not knowing violet deviates most, not understanding colour filters.