Imp Questions For All Chapters – General Science Class 8
Short Questions
1. What is reflection of light?
- Reflection is the bouncing back of light rays from a surface.
2. What are the two types of reflection?
- Regular reflection and irregular reflection.
3. What is regular reflection?
- When light reflects from a smooth surface and the rays remain parallel, forming a clear image.
4. What is irregular reflection?
- When light reflects from a rough surface, and the rays scatter in different directions.
5. What is an incident ray?
- The ray of light falling on a mirror or surface.
6. What is a reflected ray?
- The ray that bounces back after hitting a surface.
7. What is the normal line?
- A line drawn perpendicular to a surface at the point where light hits it.
8. What is the angle of incidence?
- The angle between the incident ray and the normal.
9. What is the angle of reflection?
- The angle between the reflected ray and the normal.
10. What is the first law of reflection?
- The angle of incidence = angle of reflection.
11. What is the second law of reflection?
- The incident ray, normal, and reflected ray all lie in the same plane.
12. What happens when light falls on a mirror?
- It gets reflected, following the laws of reflection.
13. Why do we see objects?
- We see objects when light reflects from them into our eyes.
14. Why can’t we see objects in a dark room?
- Because no light is available to reflect into our eyes.
15. What is a periscope?
- A device that uses two mirrors to see objects not in direct sight.
16. Which instrument works on multiple reflections?
- Kaleidoscope, which creates beautiful patterns using multiple reflections.
17. Why does a rough surface not give a clear reflection?
- Because it causes irregular reflection, scattering light in different directions.
18. What is the angle of incidence if the angle of reflection is 40°?
- 40°, because angle of incidence = angle of reflection.
19. What is the minimum number of mirrors in a periscope?
- Two mirrors, placed at 45° angles.
20. What is the function of a plane mirror?
- It forms an upright, same-size, and virtual image of an object.
Long Questions
1. What are the two types of reflection?
Reflection is of two types: Regular reflection, which occurs on a smooth surface and gives a clear image, and Irregular reflection, which happens on a rough surface and scatters light.
2. What are the laws of reflection?
The first law of reflection states that the angle of incidence is equal to the angle of reflection. The second law says that the incident ray, reflected ray, and normal lie in the same plane.
3. Why does a plane mirror form a clear image, but a rough surface does not?
A plane mirror gives a regular reflection, keeping light rays parallel, which forms a clear image. A rough surface causes irregular reflection, scattering light and making the image unclear.
4. How does a periscope work?
A periscope uses two plane mirrors placed at 45° angles to reflect light twice, allowing people to see over walls or inside submarines.
5. Why does a kaleidoscope form beautiful patterns?
A kaleidoscope has three mirrors arranged in a triangle, which create multiple reflections of colored objects, forming beautiful patterns.
6. Why can’t we see objects in a dark room?
We see objects because light reflects from them into our eyes. In a dark room, there is no light, so nothing reflects into our eyes, making objects invisible.
7. Why do we use mirrors in solar cookers?
Plane mirrors reflect sunlight and focus it on food to increase heat. This helps cook food using solar energy, making the process eco-friendly and efficient.
8. How can we prove that light follows the laws of reflection?
By shining a light ray on a plane mirror, we can measure the angle of incidence and reflection. The angles will be equal, proving the first law of reflection.
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