Electromagnetic Waves and Wave Optics: Diffraction Grating — Dispersive Power MCQ

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Diffraction Grating — Dispersive PowerHardQuestion 20255

Question

Dispersive power of a diffraction grating (dθ/dλ) for order n and grating spacing d is:

A
n/(d cosθ)
Correct
B
d cosθ/n
C
n cosθ/d
D
d/(n cosθ)

Correct answer

n/(d cosθ)

Explanation

From d sinθ = nλ, differentiating: d cosθ dθ = n dλ → dθ/dλ = n/(d cosθ). Higher order n and smaller d → higher dispersive power → better wavelength separation per unit length.

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