JEE Main · 2025 · 03 Apr 2025 · Shift 2 · Geometrical Optics

A monochromatic light of frequency

5 \times 1 0^{14} Hz

travelling through air, is incident on a medium of refractive index '2'. Wavelength of the refracted light will be :

(A)300 nm✓ Correct
(B)600 nm
(C)400 nm
(D)500 nm

Answer: (A)

Solution

Frequency is unchanged on refraction, so the vacuum wavelength is

λ = \frac{c}{f} = \frac{3 \times 1 0 ^{8}}{5 \times 1 0 ^{14}} = 600 nm

. Inside a medium the wavelength shrinks by the refractive index,

λ_{medium} = \frac{λ}{μ}

. With

μ = 2

, the refracted light has wavelength

300 nm

JEE Main · 2025 · 03 Apr 2025 · Shift 2 · Single correct option

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