Question

If the refractive index of glass with respect to air is 3/2 then the refractive
index of air with respect to glass is
(a) 4/8
(b) 3
(c) 1/3
(d) 12/18​

Answer 1

Required Answer:-

Refraction occurs because of differences of speeds of light in two media. Refractive index is defined as the ratio of speeds of light in two media when they are compared.

According to law of reversibility, the refractive index of two fixed media when compared are reciprocal to each other. That can be written as$,$

$\LARGE{ \because{ \boxed{ \sf{_a \mu \:_ g = \frac{1}{_g \mu \: _a} }}}}$

So,

Refractive index of glass wrt to air = 3/2. Then, refractive index of air with respect to glass will be 2/3.

The correct option will be Option (D) because 12/18 is the equivalent fraction of 2/3. Hence, we are done.

Answer 2

Answer:

Given :-

• Refractive index of glass with air is 3/2

To Find :-

Refractive index respect to glass

Solution :-

According to the law of reversibility

$\huge \boxed{ \sf \: a \mu g = \frac{1}{a \mu g} }$

Here,

$\sf \: \dfrac{3}{2} = \dfrac{ \dfrac{1}{3} }{2}$

$\sf \: \dfrac{1}{a \mu \: g} = \dfrac{1}{3} \times 2$

$\sf \: \dfrac{1}{ a \mu \: g} = \dfrac{2}{3}$

Now,

⅔ is not given in option

Let's find a fraction equivalent to ⅔

⅔ = 2 × 6/3 × 6 = 12/18

Hence :-

Option D