COMEDK · Physics · 26. Wave Optics

A screen is placed \(2 \mathrm{~m}\) away from a narrow slit. It the first minimum lies 5 mm from either side of the central maxima, when plane waves of wavelength \(5 \times 10^{-7} \mathrm{~m}\) are used, the slit width is

A \(4.8 \times 10^{-4} \mathrm{~m}\)
B \(2 \times 10^{-4} \mathrm{~m}\)
C \(5 \times 10^{-4} \mathrm{~m}\)
D \(24 \times 10^{-4} \mathrm{~m}\)

Verified Solution

Answer & Solution

Correct Answer

(B) \(2 \times 10^{-4} \mathrm{~m}\)

Step-by-step Solution

Detailed explanation

Given, distance between source and screen, \(D=2 \mathrm{~m}\) Distance of first minimum from the central maximum, \(y=5 \mathrm{~mm}=5 \times 10^{-3} \mathrm{~m}\) Wavelength, \(\lambda=5 \times 10^{-7} \mathrm{~m}\) We know that, \[ y_{n}=\frac{n \lambda D}{d} \] For first…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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