In Young's double slit experiment, two slits are illuminated with a light of wavelength λ. The line joining A₁ P is perpendicular to A₁ A₂ as shown in figure. If the first minimum is detected at P, the value of slits separation 'a' will be (D = distance between source and screen) (a) λ D (b) √(λ D) (c) √((λ)/(D)) (d) √((D)/(λ)) D

Answer: (b). Path difference at P: A₂P - A₁P = √(D² + a²) - D ≈ a²/2D. First minimum: a²/2D = (λ)/(2) ⇒ a = √(λ D) So the answer is (b) √(λ D).

In Young's double slit experiment, two slits are illuminated with a… | MHT CET 2026 (16 Apr, Shift 2)

Q19MHT CET 2026 · 16 APR · SHIFT 2Medium

YDSE: Film, Medium & Two Wavelengths

In Young's double slit experiment, two slits are illuminated with a light of wavelength $\lambda$ . The line joining $A_1 P$ is perpendicular to $A_1 A_2$ as shown in figure. If the first minimum is detected at P, the value of slits separation 'a' will be

(D = distance between source and screen)

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Answer: (b)

Path difference at P: $A_2P - A_1P = \sqrt{D^2 + a^2} - D \approx \dfrac{a^2}{2D}$ .
First minimum: $\dfrac{a^2}{2D} = \dfrac{\lambda}{2} \Rightarrow a = \sqrt{\lambda D}$
So the answer is (b) $\sqrt{\lambda D}$ .

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