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# Class 10 FRANK Solutions Physics Chapter 2.1 - Refraction and Total Internal Reflection of Light

Revise Frank Solutions for ICSE Class 10 Physics Chapter 2.1 Refraction and Total Internal Reflection of Light to strengthen your Physics knowledge. Our textbook solutions cover accurate answers to understand Snell’s law, refraction, refractive index etc. Through our Frank Solutions, TopperLearning’s experts guide you in plotting accurate graphs such as the graph of the angle of incidence versus the angle of reflection.

In addition, relearn the principle of reversibility of light and the concept of angle of deviation with our ICSE Class 10 Physics textbook solutions. For Physics exam preparation, you can access our video lessons, online practice tests and mock exam papers.

## Refraction and Total Internal Reflection of Light Exercise 88

### Solution 1

Refraction is the bending of light at the surface of separation, which takes when it passes from one optical medium to another optical medium with different optical densities.

### Solution 3

Yes, reflection also takes place with the refraction.

### Solution 4

When a ray of light passes from one medium to another, its direction (except for normal incidence) changes because of change in speed of light. Thus, refraction occurs because light travels with different speed in different media.

### Solution 5

The ray of light which is incident normally on the surface separating the two media passes undeviated. Such ray suffers no bending, thus, angle of refraction and angle of deviation is 0o.

### Solution 6

The phenomenon is total internal reflection

### Solution 7

Refractive index being the ratio of similar quantities has no units.

### Solution 11

Red colour of white light has least refractive index.

### Solution 12

Violet colour of white light has highest refractive index.

### Solution 13

According to the principle of reversibility, the path of a light ray is reversible.
For e.g. if light travels from air to water along a certain path, then if the path is reversed while travelling from water to air, it will follow exactly the same path.

### Solution 15

The absolute refractive index of a medium is defined as the ratio of the speed of e-m radiation in free space to the speed of radiation in that medium.

### Solution 16

When light travels from one medium (air) to another medium (glass), it bends towards the normal. The extent of bending of light depends upon the speed of light (v2) in the second medium, compared to the speed of light (v1) in the first medium. The refractive index of the second medium w.r.t. the first medium (n21) is given by
n21 = Speed of light (v1) in first medium / speed of light (v2) in second medium
The refractive index of glass is typically around 1.5, meaning that light in glass travels at
c / 1.5 = 200,000 km/s. A low value of refractive index also indicates a large critical angle at the glass-air interface.

### Solution 17

No, dispersion is not same as deviation.

### Solution 18

Angle of deviation may be defined as the angle between original path of incident ray and the path of refracted ray.

### Solution 19

The value of angle of deviation produced by a prism depends upon:
(i) The angle of incidence
(ii) The material of prism
(iii) The angle of prism
(iv) The colour of wavelength of light used.

(c) Diamond

(a) 0o

### Solution 22

Ray B is the correct refracted ray because a ray of light travelling from air (rarer medium) to water (denser medium) will bend towards the normal.

### Solution 23

The correct path is that of ray 'B'.

## Refraction and Total Internal Reflection of Light Exercise 89

### Solution 25

Factors affecting the critical angle are:
(i) The colour (or wavelength) of light.
(ii) The temperature (on changing the temperature of medium, its refractive index changes).

### Solution 26

The critical angle for a pair of media is:
(i) more than 45o for red light.
(ii) less than 45o for blue light.

### Solution 27

(a) towards the normal.
(b) away from the normal.
(c) 2/3.

### Solution 28

Critical angle is the angle of incidence in the denser medium for which the angle of refraction in the rarer medium is 90o.
Total internal reflection: When a ray of light travelling from an optically denser medium to an optically rare medium is incident at an angle greater than the critical angle for the pair of media in contact, the ray is totally reflected back into the denser medium. This phenomenon is referred as total internal reflection.
The two necessary conditions for total internal reflection to take place are:
1.    The light ray must proceed from denser to rarer medium.
2. Angle of incidence in denser medium should be greater than the critical angle for the pair of media in contact.
Relation between critical angle and r.i.: The critical angle can thus be calculated by taking the inverse-sine ratio of speed of light in denser medium and the speed of light in rarer.

### Solution 29

The critical angle for diamond is 24o; this indicates that diamond has high refractive index of 2.42. This low value of critical angle facilitates total internal reflection of each light ray entering the diamond at its multiple surfaces.

### Solution 30

Refraction is the bending of light at the surface of separation, which takes when it passes from one optical medium to another optical medium with different optical densities.
Ray diagram showing refraction of light through a glass slab:

### Solution 31

Two advantages of using total reflecting prism as a reflector in place of a plane mirror are:
(i) When total internal reflection occurs, the entire light (100%) is reflected back into the denser medium, whereas in ordinary reflection from plane mirror, some light is refracted or absorbed (i.e. reflection is partial).
(ii) Total reflecting prism gives a much brighter image than that obtained by using the plane mirror.