Primary 4 Science
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Topics Covered in This Revision Paper
- Sources of light — luminous vs non-luminous objects; natural vs man-made sources
- How we see objects — light reflected from objects into our eyes
- Properties of light — travels in straight lines, can be blocked or reflected
- Transmission of light — transparent, translucent, and opaque materials
- Shadows — formation, darkness, size, shape, length during the day
- Reflection of light — mirrors, smooth vs rough surfaces
Multiple Choice Questions
[2 marks each · 20 marks]Structured Questions
[50 marks]Sources of Light and How We See Objects
| Object | Gives out its own light? |
|---|---|
| A — The Sun | Yes |
| B — A lit torch | Yes |
| C — The Moon | No |
| D — A mirror | No |
Transmission of Light Through Materials
Sarah placed four different materials between a torch and a screen, one at a time. She observed what happened to the light.
| Material | Type | Observation |
|---|---|---|
| P — Clear glass | Transparent | Bright shadow / almost no shadow |
| Q — Frosted plastic | Translucent | Faint, lighter shadow |
| R — Cardboard | Opaque | Dark, clear shadow |
| S — Thin tissue paper | Translucent | Faint, lighter shadow |
Shadows — Formation, Size, and Shape
(i) The ball is moved closer to the torch? [1]
(ii) The ball is moved closer to the screen? [1]
Shadow Length During the Day
A tree stands in an open field. The position of the Sun changes throughout the day.
| Morning (7 am) | Noon (12 pm) | Evening (5 pm) |
|---|---|---|
Reflection of Light and Mirrors
Amy shone a torch at different surfaces and observed what happened to the light.
| Surface | Type | Observation |
|---|---|---|
| X — Plane mirror | Smooth, shiny | Light is reflected clearly in one direction. |
| Y — White paper | Rough, matte | Light is scattered in many directions. |
Answer Key
Section A — Multiple Choice
Section B — Structured Questions
(a) Luminous objects: The Sun (A), a lit torch (B). Non-luminous objects: The Moon (C), a mirror (D).
(b) The Moon does not give out its own light. We see it because sunlight is reflected off the surface of the Moon into our eyes.
(c) Light from us (reflected from a light source) hits the mirror and is reflected back to our eyes, forming an image.
(d) Natural source: The Sun / firefly. Man-made source: torch / light bulb / candle / glow stick.
(a) Clear glass (P) allows the most light to pass through.
(b) Cardboard is opaque, so it blocks all light from passing through. Frosted plastic is translucent, so it allows some light to pass through. Therefore, the shadow formed by cardboard is darker because no light reaches behind it, while the shadow formed by frosted plastic is lighter because some light still passes through.
(c) Transparent: windows / glass bottles (to let light in). Opaque: walls / roofs / umbrellas (to block light).
(a) Three things needed: (1) A light source that gives off light. (2) An opaque or translucent object that blocks some or all of the light travelling in straight lines. (3) A surface/screen on which the shadow is formed.
(b)(i) The shadow becomes bigger.
(ii) The shadow becomes smaller.
(c) The shape of the shadow changes. This is because the shadow takes the shape of the side of the object that faces the light source. When the car is turned, a different side faces the torch, so the shadow changes shape.
(a) The shadow is shortest at noon because the Sun is directly overhead, so the tree blocks light in a small area directly beneath it.
(b) The shadow is longest in the morning (7 am) and evening (5 pm) because the Sun is near the horizon and its rays hit the tree at a low angle, causing the shadow to stretch out further across the ground.
(c) In the morning, the shadow points West (opposite to where the Sun rises in the East).
(d) In the evening, the shadow points East (opposite to where the Sun sets in the West).
(a) Light is reflected in one direction (regular reflection).
(b) A plane mirror has a smooth, shiny surface that reflects light clearly in one direction, forming a clear image. White paper has a rough surface that scatters light in many directions, so no clear image is formed.
(c) Bathroom mirror / looking glass / rear-view mirror on vehicles / periscope / dressing table mirror.
(d) Light from above the water hits the top mirror and is reflected down the tube. It then hits the bottom mirror and is reflected again into the person's eyes, allowing them to see above the water while staying underwater.