Question

. You are given three media A, B and C of refractive index 1.5, 2.42 and 1.46. The medium in which the light will travel fastest is *



A

B

C

equal in all three media

​

Answer 1

◘ Given ◘

$\bigstar$ Refractive index of medium A = 1.5

$\bigstar$ Refractive index of medium B = 2.42

$\bigstar$ Refractive index of medium C = 1.46

◘ To Find ◘

The medium in which the light will travel fastest.

◘ Solution ◘

We know,

Refractive index (RI) is the ratio of speed of light in vacuum to the speed of light in that medium.

RI = speed of light in vacuum / speed of light in that medium

From the above relationship, we get :

• RI ∝ speed of light in vacuum

→ If speed of light in vacuum is more, then RI is more & vice-versa.

And

• RI ∝ 1/speed of light in that medium

→ If speed of light in vacuum is more, then RI is less & vice-versa.

_________________

According to the question, the lowest RI is 1.46.

From above, we know that lower the RI, higher the speed of light in the medium.

RI of C is 1.46. Therefore, light travels the fastest in medium C.

Answer 2

ANSWER :-

➵ medium c is the correct answer.

Reason :- speed of light ∝ 1/optical density

or n ∝ 1/v

Because the refractive index is inversely proportional to speed of light fans if we increase the refractive index the speed of light will be less , and if we decrease the refractive index the speed of light will be more.

REFRACTIVE INDEX :-

➵ Ratio of speed of light in air to the speed of light in given medium.

➵ It has no S.I units.

➵ The refractive index for absolute Refractive Index of a medium (say,m) , denoted by μm is defined as follows:

$\dag \boxed{ \bf \red{ \mu_{m = \frac{speed \: of \: light \: in \: vaccum \: or \: air}{speed \: of \: light \: in \: the \: given \: medium} = \frac{c}{v_{m}} }}}$

➵ vacuum has less refractive index.

➵ Diamond has higher optical density.

➵ vacuum has lowest optical density.

➵ Diamond has higher refractive index.