JEE Main · 2026 · 22 Jan 2026 · Shift 2 · Geometrical Optics

The wavelength of light, while it is passing through water is 540 nm. The refractive index of water is

\frac{4}{3}

. The wavelength of the same light when it is passing through a transparent medium having refractive index of

\frac{3}{2}

____

nm.

Answer: (C)

Solution

Frequency is unchanged as light crosses from one medium to another, so the product

μ λ

is constant:

μ_{1} λ_{1} = μ_{2} λ_{2}

. With

μ_{1} = \frac{4}{3}

(water),

λ_{1} = 540 nm

and

μ_{2} = \frac{3}{2}

λ_{2} = \frac{μ _{1} λ _{1}}{μ _{2}} = \frac{( 4/3 ) ( 540 )}{3/2} = 480 nm .

The wavelength in the new medium is

480 nm

JEE Main · 2026 · 22 Jan 2026 · Shift 2 · Single correct option