Light rays from the sun after reflection at a plane mirror pass through a hole in a wall. After some time due to the shift in the position of the sun, the angle of incidence of sunlight increased by $10^{0}$ . By what angle should the mirror be rotated such that the reflected rays continue to pass through the hole in the wall?

20^{0}

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15^{0}

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5^{0}

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10^{0}

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Solution

The correct option is C $5^{0}$
It is to be noted that when a mirror is rotated by an angle $θ$ then reflected ray gets deviated by an angle $2 θ$ .
Hence there is an increase of $10^{0}$ in both sides , hence by rotating the mirror by $5^{0}$ we can make the reflected light ray pass through the hole in the wall.

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Question 6

Two mirrors A and B are placed at right angles to each other as shown in the figure.

A ray of light incident on mirror A at an angle of $25^{\circ}$ falls on mirror B after reflection. The angle of reflection for the ray reflected from mirror B would be
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(d) $100^{\circ}$

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The correct option is C 50It is to be noted that when a mirror is rotated by an angle θ then reflected ray gets deviated by an angle 2θ.Hence there is an increase of 100 in both sides , hence by rotating the mirror by 50 we can make the reflected light ray pass through the hole in the wall.