Page 170 - Science Class 08

E. Write the correct term for.
1. a material through which light can pass : _____________________

2. a medium in which light travels faster : _____________________
3. a medium in which light travels slower : _____________________
4. the perpendicular drawn at the point of incidence : _____________________

5. the ra o between the veloci es of light in two mediums : _____________________
6. the degree of thickness of a medium for light : _____________________
7. deflec on of light-rays from their straight path : _____________________
8. the angle at which a ray strikes a new medium : _____________________

9. the angle at which a ray deflects inside a new medium : _____________________
10. the angle at which a ray emerges form a new medium : _____________________
11. the distance between two corresponding

points on adjoining waves : _____________________
12. patch of seven visible colours in which white light splits : _____________________
F. Short answer ques ons.
1. What is refrac on of light? Why does it take place and what does it depend upon?

2. What is meant by refrac ve index? Explain with examples.
3. How do rays of light refract through a glass slab? Give a clear diagram and explain it well.
4. How do rays of light disperse and when? What is the reason behind the forma on of a
rainbow?
5. How will you prove that white light is composed of seven visible colours?

6. Explain the refrac on of light through a prism giving a clear diagram.
G. Long answer ques ons.
1. Speed of light is slower in water than in air. Explain.
2. A pencil placed in a tumbler with water in it appears bent. Explain.

3. A rainbow is o en formed in the sky during the rainy season. Explain.
4. Why a light-ray falling perpendicular on a medium does not refract?
5. Why white light splits into its components colours a er passing through a prism?

Project
Project ActivityActivityActivity
Project
Project Activity
Explain the refrac on of a light-ray that strikes a glass slab in a slan ng manner, i.e. at an angle
other than a right angle.

HO
HO
HOTSTSTS
HOTS
If all objects around us were to reflect light in a regular way, what problems might we face?

170 Science-8