JEE Main · 2023 · 15 Apr 2023 · Shift 1 · Wave Optics

A single slit of width

a

is illuminated by a monochromatic light of wavelength 600 nm. The value of 'a' for which first minimum appears at

θ = 3 0^{\circ}

on the screen will be :

(A) $0.6 μ m$
(B) $1.2 μ m$ ✓ Correct
(C) $1.8 μ m$
(D) $3 μ m$

Answer: (B)

Solution

The first minimum in single-slit diffraction satisfies

a sin θ = λ

. With

θ = 3 0^{\circ}

and

λ = 600 nm

a = \frac{λ}{sin 3 0 ^{\circ}} = \frac{600 \times 1 0 ^{- 9}}{0.5} = 1.2 \times 1 0^{- 6} m

, so the slit width is

1.2 μ m

JEE Main · 2023 · 15 Apr 2023 · Shift 1 · Single correct option

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