The angular separation of the central maximum in the Fraunhofer diffraction pattern is measured. The slit is illuminated by the light of wavelength 6000. If the slit is illuminated by light of another wavelength, the angular separation decreases by 20%. The wavelength of light used is (a) 6400 (b) 5600 (c) 4800 (d) 4400

Answer: (c). Angular width of central maximum = (2λ)/(a), so for the same slit it is proportional to λ. A 20% decrease in angular width means λ' = 0.8λ = 0.8 × 6000. So the answer is (c) 4800.

The angular separation of the central maximum in the Fraunhofer… | MHT CET 2024 (16 May, Shift 1)

Q28MHT CET 2024 · 16 MAY · SHIFT 1Easy

Diffraction at a Single Slit

The angular separation of the central maximum in the Fraunhofer diffraction pattern is measured. The slit is illuminated by the light of wavelength $6000\text{ \AA}$ . If the slit is illuminated by light of another wavelength, the angular separation decreases by $20\%$ . The wavelength of light used is

Show answer and solution

Answer: (c)

Angular width of central maximum $= \dfrac{2\lambda}{a}$ , so for the same slit it is proportional to $\lambda$ .
A $20\%$ decrease in angular width means $\lambda' = 0.8\lambda = 0.8 \times 6000\text{ \AA}$ .
So the answer is (c) $4800\text{ \AA}$ .

Report a mistake

Diffraction at a Single Slit question from MHT CET 2024 (16 May, Shift 1)

More questions on Diffraction at a Single Slit