Question

For the same angle of incidence in media A,B and C, the angles of refraction are 20degree
, 30degree

and 40 degree

respectively. In

which medium will the velocity of light be maximum? Give reason in support of your answer.

Answer 1

As sini/sinr = u

More the r more the sinr therefore lesser will be refractive index

As refractive index is inversely proportional to speed in medium

therefore lesser the refractive index more thr speed

Therefore 40 degree will have maximum speed

Answer 2

Answer: the one in which r = 40 degrees

Explanation:

When light enters from one medium to another, its speed changes. The speed decreases when it enters a denser medium and increases when it enters a rarer medium.

The relation between angle of incidence and angle of refraction is given by Snell's law.

$\frac{\text{sin r}}{\text{sin i}}=\frac{n_1}{n_2}$

Since, the angle of incidence is same and medium from which light is entering, we can draw a relation:

$\text{sin r}\propto\frac{1}{n_2}$

Greater the angle, less is the density of the medium and hence greater is the velocity of light.

Since, sin 40 > sin 30> sin 20

n(40)<n(30)<n(20)

v (40)  > v (30)> v (20)

Thus, velocity of light is maximum in the medium in which the angle of refraction is 40 degrees.