Question

For the same angle of incidence in media A, and C , the angles of refraction are 20°, 30°, and 40° respectively. In which medium will the velocity of light be maximum ? Give reason in support of your answer.

Answer 1

answer : In medium C will the velocity of light be maximum.

explanation : from Snell's law,

$\mu_isini=\mu_rsinr$

here, $\mu_i$ denotes refractive index of medium of incidence angle , i denotes incidence angle , $\mu_r$ denotes refractive index of medium of refraction angle and r denotes refraction angle.

if first medium is air then, $\mu_i=1$

then, $sini=\mu_rsinr$

$\mu_r=\frac{sini}{sinr}$

here, it is clearly shown that refractive index depends on angle of incidence and angle of refraction.

if incidence angle remains constant then, refractive index of medium depends only on angle of refraction. e.g., refractive index is inversely proportional to angle of refraction.

here, angle of refraction in medium A = 20°, in medium B = 30° and in medium C = 40°

maximum angle of refraction in medium C

so, refractive index of medium C is minimum.

we know, velocity of light is inversely proportional to refractive index of medium. e.g., $v=\frac{c}{\mu}$

where v is velocity of light in medium, c is velocity of light in vaccum and $\mu$ is refractive index of medium.

since, refractive index of medium C is minimum.so, velocity of light will be maximum in medium C.

Answer 2

the answer is 40° bcs (SINi IS DIRECTLY PROPORTIONAL TO V)