All questions of Light for Year 4 Exam

Understanding Light and Rough Surfaces
When light strikes a rough surface, it behaves differently than when it hits a smooth surface. Here's a detailed explanation of what happens:
Reflection of Light
- When light encounters a rough surface, it doesn't reflect in a single direction.
- Instead, it scatters in multiple directions due to the uneven texture of the surface.
Why It Scatters
- A rough surface has many tiny bumps and grooves.
- Each of these imperfections reflects light at different angles.
Resulting Effect
- This scattering of light causes the surface to appear dull rather than shiny.
- It prevents the formation of a clear image, which would only occur with smooth surfaces that reflect light uniformly.
Examples of Rough Surfaces
- Examples include concrete, wood, or any unpolished material.
- These surfaces are good at diffusing light, which is why they don't create clear reflections.
Conclusion
- Therefore, when light strikes a rough surface, it is reflected in multiple directions, which is the reason option 'C' is the correct answer.
- This understanding helps in various fields, such as photography and design, where the texture of materials plays a critical role in how light interacts with them.
By knowing how light behaves on different surfaces, we can better comprehend the world around us!

Understanding Earth's Rotation
The Earth’s rotation plays a crucial role in how shadows are formed and behave throughout the day.
How Shadows Form
- Shadows are created when an object blocks light from a source, like the Sun.
- As the Earth rotates on its axis, different areas receive varying amounts of sunlight.
Movement of Shadows
- As the Sun rises in the east and sets in the west, the position of sunlight changes.
- This change causes shadows to move in the opposite direction of the Sun’s position.
Changing Length of Shadows
- At sunrise and sunset, shadows are longer because the Sun is lower in the sky.
- At noon, when the Sun is highest, shadows become shorter.
- The rotation of the Earth leads to these variations in shadow length and position.
Conclusion
- Thus, option 'B' is correct: it causes shadows to move and change length.
- Understanding this concept helps us appreciate how the Earth's rotation affects our daily experiences, like the way shadows appear around us.

Understanding Light Absorption and Reflection
When we talk about how different surfaces interact with light, it is important to understand the concepts of absorption and reflection.
Reflection vs. Absorption
- Reflection occurs when light bounces off a surface.
- Absorption happens when a surface takes in light rather than reflecting it.
Characteristics of Surfaces
1. Shiny Surfaces:
- These surfaces, such as mirrors or polished metals, reflect most of the light that hits them.
2. Rough or Uneven Surfaces:
- These surfaces scatter light in multiple directions, which causes them to absorb more light.
- Examples include concrete or unpolished wood.
3. Smooth Surfaces:
- Similar to shiny surfaces, smooth surfaces can reflect light well, especially if they are also shiny.
4. Transparent Surfaces:
- These allow light to pass through rather than absorb it. Glass is a common example.
Why Rough Surfaces Absorb Light
- Increased Surface Area: Rough surfaces have a greater surface area compared to smooth surfaces, allowing more light to be absorbed.
- Scattering Effect: The irregularities in a rough surface cause light to scatter, reducing the amount of light that can bounce back, hence increasing absorption.
In conclusion, rough or uneven surfaces (option B) are more likely to absorb light rather than reflect it, making them distinct from shiny, smooth, or transparent surfaces.