When wavefronts pass from denser medium to rarer medium, the width of the wavefront (a) increases. (b) may increase or decrease. (c) decreases. (d) remains unchanged.

Answer: (c). For the same length L of the interface: incident width = Lcos i, refracted width = Lcos r. Going from denser to rarer, the ray bends away from the normal: r > i. So cos r < cos i and the refracted wavefront is narrower. So the answer is (c) decreases.

When wavefronts pass from denser medium to rarer medium, the width of… | MHT CET 2024 (3 May, Shift 1)

Q13MHT CET 2024 · 3 MAY · SHIFT 1Easy

Wave Theory, Wavefronts & Doppler Effect

When wavefronts pass from denser medium to rarer medium, the width of the wavefront

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Answer: (c)

For the same length $L$ of the interface: incident width $= L\cos i$ , refracted width $= L\cos r$ .
Going from denser to rarer, the ray bends away from the normal: $r > i$ .
So $\cos r < \cos i$ and the refracted wavefront is narrower.
So the answer is (c) decreases.

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