Primary 6 PSLE Science Light Quiz

Primary 6 PSLE Science Quiz - Light

Answer Key

Section A: Multiple Choice Questions

1. (c) straight [2]
Reasoning: Light travels in a straight line. This is a fundamental property of light and is the reason shadows are formed.

2. (c) A glowing candle flame [2]
Reasoning: A luminous object is one that produces its own light. The Moon and a mirror only reflect light. A wooden table does not produce light. The candle flame produces light through combustion.

3. (c) reflected [2]
Reasoning: When light strikes a smooth, shiny surface (such as a mirror), it bounces off — this is called reflection. The surface does not absorb most of the light, nor does it transmit it.

4. (b) light travels in straight lines and cannot pass through the opaque object [2]
Reasoning: Because light travels in straight lines, it cannot bend around an opaque object. The region behind the object where light cannot reach forms the shadow.

5. (b) refraction of light [2]
Reasoning: Refraction is the bending of light as it passes from one medium (air) to another (water) at an angle. This change in speed causes the pencil to appear bent at the water surface.

6. (d) Red [2]
Reasoning: In the visible spectrum (ROYGBIV), red has the longest wavelength (~700 nm) and violet has the shortest (~400 nm).

7. (d) seven [2]
Reasoning: White light is composed of seven colours: Red, Orange, Yellow, Green, Blue, Indigo, and Violet. This can be demonstrated using a prism.

8. (d) inverted and diminished [2]
Reasoning: 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, producing an inverted image. The image is also typically smaller (diminished) than the object.

9. (c) blurrier and brighter [2]
Reasoning: A larger pinhole allows more light rays (from different points on the object) to reach the same point on the screen, causing the image to become blurred. However, more light passes through, so the image is brighter.

10. (c) Clear glass [2]
Reasoning: Clear glass is a transparent material that allows most light to pass through. A brick wall and wooden board are opaque. Tissue paper is translucent — it allows some light through but scatters it.

Section B: Short-Answer Questions

11. Any two of the following, 1 mark each [2]:

• Light travels in a straight line.
• Light can be reflected.
• Light can be refracted.
• Light travels at high speed (approximately 3 × 10⁸ m/s in air/vacuum).
• White light is made up of seven colours.
• Light can be absorbed by objects.

Marking note: Accept any two valid properties. Do not award marks for vague answers like "light is bright" without further qualification.

12.
(a) [1] The normal is the line perpendicular (at 90°) to the mirror surface at the point where the light ray hits. The incident ray is the incoming ray approaching the mirror. The reflected ray is the ray bouncing off the mirror.
Marking note: Award 1 mark if all three are correctly identified/indicated on the diagram.

(b) 35° [1]
Reasoning: According to the law of reflection, the angle of incidence equals the angle of reflection. Since the angle of incidence is 35°, the angle of reflection is also 35°.

13. [2]
When the object is placed closer to the light source, the light rays from the source spread out more (diverge more) before reaching the object. This means the object blocks a wider cone of light behind it, resulting in a larger shadow. Conversely, when the object is farther from the light source, the rays are more parallel, and the shadow is smaller.

Marking note: Award 2 marks for a clear explanation linking the closeness to the light source with the spreading/divergence of light rays and the resulting larger shadow. Award 1 mark for a partially correct answer (e.g., only stating "light spreads out more" without linking to shadow size).

14.
(a) Dispersion [1]
Reasoning: Dispersion is the splitting of white light into its constituent colours.

(b) Red, Orange, Yellow, Green, Blue, Indigo, Violet [1]
Marking note: Award 1 mark only if all seven colours are listed in the correct order, starting from the outermost (red). Accept the acronym ROYGBIV.

15. [3] — 1 mark each:

Reasoning:

• Transparent materials allow most light to pass through (clear plastic).
• Translucent materials allow some light through but scatter it (tissue paper).
• Opaque materials do not allow light to pass through (brick wall).

16.
(a) Towards the normal [1]
Reasoning: When light travels from a less optically dense medium (air) into a more optically dense medium (glass), it slows down and bends towards the normal.

(b) Light slows down when it enters glass (a denser medium), causing it to bend towards the normal. [1]
Marking note: The answer must mention that glass is denser / light slows down in glass. Simply repeating "towards the normal" is not sufficient for part (b).

17.
(a) The three holes must be in a straight line (aligned). [1]
Reasoning: For light from the candle to pass through all three holes and reach the screen, the holes must be arranged in a straight line.

(b) This experiment demonstrates that light travels in a straight line. [1]
Reasoning: If light could travel in curved paths, the holes would not need to be aligned for the candle to be visible on the screen.

Section C: Structured / Application Questions

18.
(a) [2] The light ray should travel from the object downward at an angle, strike Mirror 1, reflect downward through the tube, strike Mirror 2, and reflect into the eye. The direction arrows should show the correct path.
Marking note: Award 2 marks for a correctly drawn ray path with direction arrows. Award 1 mark for a partially correct path (e.g., correct general direction but missing arrows or one incorrect reflection).

(b) Each mirror should be placed at 45° to the vertical. [1]
Reasoning: At 45°, the angle of incidence equals the angle of reflection, allowing light to be redirected by 90° at each mirror, making the periscope functional.

(c) Any one of the following [1]:

• Used in submarines to see above the water surface.
• Used in armoured vehicles to observe from behind cover.
• Used in crowded events to see over people's heads.

19.
(a) [2] As the distance between the torch and the block increases, the length of the shadow decreases. The relationship is inversely related — the farther the torch is from the block, the shorter the shadow becomes.

Marking note: Award 2 marks for stating the inverse relationship clearly with reference to the data. Award 1 mark for stating only one aspect (e.g., "shadow gets shorter") without mentioning the trend clearly.

(b) [2] Predicted length: approximately 8–9 cm.
Reasoning: From the data, as the distance increases by 10 cm, the shadow length decreases, but the rate of decrease is slowing down (from 28→16 = −12, 16→12 = −4, 12→10 = −2). Following this pattern, the next decrease would be smaller, so the shadow at 50 cm would be approximately 8–9 cm.

Marking note: Accept any answer between 7 cm and 10 cm with a valid reason. Award 1 mark for the prediction and 1 mark for the reasoning.

(c) [1] Any one of the following:

• The height/size of the wooden block.
• The angle at which the torch is held.
• The brightness of the torch.
• The distance between the block and the screen.
• The surface on which the shadow is projected.

Marking note: The variable must be one that could affect the length of the shadow if changed. Do not accept "the distance between torch and block" as that is the independent variable being tested.

20.
(a) Spectrum [1]
Reasoning: The band of colours produced when white light passes through a prism is called a spectrum.

(b) [2] White light is made up of seven different colours, each with a different wavelength. When white light enters the prism, each colour travels at a slightly different speed in the glass and is refracted (bent) by a different amount. This causes the colours to separate and spread out into a spectrum.

Marking note: Award 2 marks for mentioning that white light has multiple colours AND that each colour is refracted by a different amount. Award 1 mark for mentioning only one of these points.

(c) [2] Different colours of light have different wavelengths. Red light has the longest wavelength and is refracted the least, while violet light has the shortest wavelength and is refracted the most. Since each colour bends by a different amount in the prism, they separate to form the spectrum.

Marking note: Award 2 marks for correctly linking wavelength to the degree of bending/refraction. Award 1 mark for mentioning that different colours have different wavelengths without linking to refraction, or for stating that red bends least and violet bends most without explanation.

Mark Summary

This quiz was generated as syllabus-aligned practice content. It is not derived from past-year examination papers but is designed to reflect the style and difficulty of PSLE Science questions on the topic of Light.