Refraction of Light Class-8th Goyal Brothers Physics Solutions Chapter-5 (Light Energy), unit-3 (Refraction of Light). We Provide Step by Step Answers of Objective, True False, Incorrect and Correct, Fill in the blanks, Match the following , Short/Long Answer Type of Chapter-5 (Light Energy), unit-3 (Refraction of Light) Visit official Website CISCE for detail information about ICSE Board Class-8.
Refraction of Light Class-8th Goyal Brothers ICSE Physics Solution Chapter-5 Unit-3
| Board | ICSE |
| Class | 8th |
| Subject | Physics |
| Book Name | Goyal Brothers |
| Chapter-5 | Light Energy |
| Unit-3 |
Refraction of Light |
| Topic | Solution of exercise questions |
| Session | 2023-24 |
OBJECTIVE QUESTION
Refraction of Light Class-8th Goyal Brothers ICSE Physics Solution Chapter-5 Unit-3
Que: A. Fill in the blank spaces by choosing the correct words from the list given below :
List : Refractive index, refracted, normally, deviates, less
1. The phenomenon due to which a ray of light deviates from its path while travelling from one optical medium to another optical medium is called refraction.
2. The incident ray, the refracted ray and the normal lie in the same plane during refraction.
3. When a ray of light strikes the surface of separation of two optical media normally it does not suffer any refraction.
4. The ratio of velocity of light in vacuum to the velocity of light in a given media is called refractive index.
5. When a ray of light travels from an optically more denser medium to an optically less denser medium, the angle of incidence is always less than the angle of refraction.
Que: B. Statements given below are incorrect. Write the correct statements :
Question: 1. When a ray of light travels from optically denser medium to optically rarer medium, it always bends towards the normal.
Answer: When a ray of light travels from optically denser medium to optically rarer medium, it always bends away the normal.
Question: 2. A ray of light is incident perpendicularly on a glass slab. The angle of incidence is 90°.
Answer: A ray of light is incident perpendicularly on a glass slab. The angle of incidence is 0°.
Question: 3. The ratio between the velocity of light in a given optical medium to the velocity of light in vacuum is called refractive index.
Answer: The ratio between the velocity of light in a vacuum to the velocity of light in media is called refractive index.
Question: 4. When a ray of light travels from an optically less denser medium to an optically more denser medium, the angle of incidence is always less than angle of refraction.
Answer: When a ray of light travels from an optically less denser medium to an optically more denser medium, the angle of incidence is always more than angle of refraction.
Question: 5. During refraction through a glass block, with the increase in angle of incidence, the angle of refraction decreases.
Answer: During refraction through a glass block, with the increase in angle of incidence, the angle of refraction increases.
Que: C. Write ‘True’ or ‘False’ for the following statements :
| Statement | True/False |
| 1. A ray of light striking normally on another optical medium does not suffer refraction. | T |
| 2. The angle of incidence is always smaller than angle of refraction when a ray travels from air to glass. | F |
| 3. The ratio between velocity of light in vacuum to velocity of light in air is called refractive index. | T |
| 4. A ray travelling from glass to air, bends away from the normal. | T |
| 5. A pencil held obliquely in water appears bent and longer. | F |
Que: D. Tick (√) the most appropriate answer :
1. A ray of light travelling in air strikes the surface of glass at angle of 45°. The angle of refraction in the glass will be :
(a) less than 45°
(b) more than 45°
(c) zero
(d) none of these
Answer: option (a) less than 45° is correct.
2. A ray of light incident on glass slab finally emerges out of it. The ray which emerges out is called.
(a) incident ray
(b) refracted ray
(c) emergent ray
(d) none of these
Answer: option (c) emergent ray is correct.
3. A ray of light travelling obliquely from glass to air :
(a) bends towards the normal
(b) bends away from the normal
(c) does not deviate from its path
(d) none of these
Answer: option (a) bends towards the normal is correct.
4. When a coin placed in a bowl of water and seen from above, it appears :
(a) raised from its position
(b) below its position
(c) at the same position
(d) none of these
Answer: option (a) raised from its position is correct.
5. When a ray of light strikes the glass slab at 90°, it is seen that it does not deviate from its path. In such a situation :
(a) angle of incidence is zero
(b) angle of refraction is zero
(c) both (a) and (b)
(d) none of these
Answer: option (c) both (a) and (b) is correct.
Que: E. Match the statements in Column A, with those in Column B :
| Column A | Column B |
| 1. The deviation of rays of light from their path on passing from one medium to another. | (a) Incident ray |
| 2. The name of ray which travels along a different path on passing through a glass slab. | (b) Refraction of light |
| 3. The name of the ray which travels toward an optical medium of a different nature. | (c) Angle of refraction |
| 4. The ratio of speed of light in vacuum to speed of light in a given optical medium. | (d) Refracted ray |
| 5. The angle which a refracted ray makes with normal. | (e) Refractive index |
Answer:
| Column A | Column B |
| 1. The deviation of rays of light from their path on passing from one medium to another. | (a) Refraction of light |
| 2. The name of ray which travels along a different path on passing through a glass slab. | (b) Refracted ray |
| 3. The name of the ray which travels toward an optical medium of a different nature. | (c) Incident ray |
| 4. The ratio of speed of light in vacuum to speed of light in a given optical medium. | (d) Refractive index |
| 5. The angle which a refracted ray makes with normal. | (e) Angle of refraction |
STUDY QUESTION
Refraction of Light Class-8th Goyal Brothers ICSE Physics Solution Chapter-5 Unit-3
Question: 1. What do you understand by the term ‘refraction of light’?
Answer: The bending of a ray of light obliquely on a surface when it passes from one medium to another is called refraction.
Question: 2. Why is a coin placed in a bowl of water appears raised ?
Answer: This is because of refraction of light. As light passes from water to air, it bends away from the normal. The refracted rays appear to come from a point above the actual position of the coin, hence the coin appears raised.
Question: 3. Define the following with reference to refraction of light:
(a) incident ray
Answer: An incident ray is a rectilinear ray of light that strikes a surface, known as incident ray on that spot(surface). The angle between this ray and the perpendicular or normal to the surface is the angle of incidence.
(b) refracted ray
Answer: Refracted rays can be defined as the part of rays that moves after deviation in the medium after ray incident on its boundary from a another medium.
(c) normal
Answer: Imaginary straight line perpendicular to the refracting surface at the point of refraction.
(d) emergent ray
Answer: An emergent ray seems to be a refracted beam that originates from a medium or channel after refraction.
(e) angle of incidence
Answer: Angle between the incident ray and the normal.
(f) angle of refraction
Answer: Angle between the refracted ray and the normal.
Question: 4. State the laws of refraction of light. State at least three example of refraction of light.
Answer: Laws of refraction state that: The incident ray refracted ray, and the normal to the interface of two media at the point of incidence all lie on the same plane. The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant. This is also known as Snell’s law of refraction.
- Twinkling of stars in a clear sky.
- Pool of water appears to be less deep than it actually is.
- Rainbow formation in the sky.
Question: 5. How are the angle of incidence and angle of refraction related to each other when:
(a) a ray of light travels from rare to dense medium?
Answer: (a) When a light Ray travels from rarer to denser medium. It shifts toward normal and angle of refraction is smaller than that of angle of incidence.
(b) a ray of light travels from dense to rare medium?
Answer: (b) When light Ray travels from denser to rarer medium it shifts away from normal and angle of incidence is greater than that of refraction.
Question: 6. (a) What do you understand by the term refractive index?
Answer: Refractive index, also called index of refraction, measure of the bending of a ray of light when passing from one medium into another.
(b) If the velocity of light in vacuum is 3 × 108 ms¯¹ and in another medium M is 0.75 × 108 ms¯¹, what is the refractive index of M?
Answer: Given: Speed of light in medium (v2) = 0.75 × 108 m/s,
velocity of light in vacuum (v1) = 3 × 108 m/s
To find: Absolute refractive index (n)
Formula: n = v¹/v²
Calculation: From the formula,
n = 3 × 108 m/s/0.75 × 108 m/s
n = 4
The absolute refractive index of the medium is 4
— : end of Refraction of Light Class-8th Goyal Brothers ICSE Physics Solution Chapter-5 Unit-3:–-
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