Two plane mirrors are inclined to each other such that a ray of light… | JEE Main 2019 (9 Jan, Shift 2)

Q42JEE Main 2019 · 9 JAN · SHIFT 2Medium

Reflection & Mirrors

Two plane mirrors are inclined to each other such that a ray of light incident on the first mirror (M1) and parallel to the second mirror (M2) is finally reflected from the second mirror (M2) parallel to the first mirror (M1). The angle between the two mirrors will be:

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Answer: (b)

Let the angle between the mirrors be $\theta$ . The incoming ray is parallel to M2, so it makes $\theta$ with M1 and leaves M1 also at $\theta$ .
In the triangle formed by the mirrors and the ray, the ray meets M2 at $180^\circ - 2\theta$ and leaves at the same angle.
Parallel to M1 means this angle equals $\theta$ : $180^\circ - 2\theta = \theta$
$\theta = 60^\circ$ , so the answer is (b).

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Reflection & Mirrors question from JEE Main 2019 (9 Jan, Shift 2)

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