Wave Optics

JEE Main level, single correct, medium

127 of 191

Question 127 of 191

Which of the following are true for a single slit diffraction?
A. Width of central maxima increases with increase in wavelength keeping slit width constant.

B. Width of central maxima increases with decrease in wavelength keeping slit width constant.

C. Width of central maxima increases with decrease in slit width at constant wavelength.

D. Width of central maxima increases with increase in slit width at constant wavelength.

E. Brightness of central maxima increases for decrease in wavelength at constant slit width.

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Answer: (A) A, C, E only

For single slit diffraction, linear width of central maximum is W=2λDaW = \frac{2\lambda D}{a}.
A: Width increases with wavelength (keeping
aa constant) - TRUE since W∝λW \propto \lambda.
B: Width increases with decreasing wavelength - FALSE, opposite of A.

C: Width increases with decreasing slit width (keeping
λ\lambda constant) - TRUE since W∝1aW \propto \frac{1}{a}.
D: Width increases with increasing slit width - FALSE, opposite of C.

E: Brightness increases with decreasing wavelength at constant slit width - TRUE since less wavelength means less diffraction spreading and more concentrated intensity.

Statements A, C, and E are true.

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