In a Fraunhofer diffraction at a single slit of width 'd' and incident light of wavelength 5500, the first minimum is observed at an angle 30°. The first secondary maxima is observed at an angle θ, equal to (a) sin ⁻¹(1/4) (b) sin ⁻¹(3/4) (c) sin ⁻¹(√(3)/2) (d) sin ⁻¹(1/√(2))

Answer: (b). First minimum: dsin 30° = λ ⇒ d = 2λ. First secondary maximum: dsin θ = (3λ)/(2) ⇒ sin θ = 3/4. So the answer is (b) sin ⁻¹(3/4).

In a Fraunhofer diffraction at a single slit of width 'd' and… | MHT CET 2022 (11 Aug, Shift 2)

Q54MHT CET 2022 · 11 AUG · SHIFT 2Easy

Diffraction at a Single Slit

In a Fraunhofer diffraction at a single slit of width 'd' and incident light of wavelength $5500\text{ \AA}$ , the first minimum is observed at an angle $30^\circ$ . The first secondary maxima is observed at an angle $\theta$ , equal to

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Answer: (b)

First minimum: $d\sin 30^\circ = \lambda \Rightarrow d = 2\lambda$ .
First secondary maximum: $d\sin\theta = \dfrac{3\lambda}{2} \Rightarrow \sin\theta = \dfrac{3}{4}$ .
So the answer is (b) $\sin^{-1}\left(\frac{3}{4}\right)$ .

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