1. **Problem Statement:** Two light rays emitted by a light source are reflected by two plane mirrors M_1 and M_2 arranged at a right angle (90°). One ray reflects off M_1 at an angle of 15° and then off M_2. The other ray reflects directly off M_2. We need to find the angle between the two rays reflected by M_2. 2. **Key Concept:** The law of reflection states that the angle of incidence equals the angle of reflection. Also, when two mirrors are at 90°, the angle between rays reflected from each mirror can be found by considering the geometry of reflections. 3. **Step-by-step solution:** - The first ray hits M_1 at 15°, so it reflects off M_1 at 15° (angle of incidence = angle of reflection). - After reflection from M_1, this ray travels towards M_2. Since M_1 is horizontal and M_2 is vertical, the ray now hits M_2 at an angle of 15° relative to the normal of M_2. - It reflects off M_2 at the same 15° angle. - The second ray hits M_2 directly and reflects off it. Since the light source is positioned such that this ray hits M_2 at 90° - 15° = 75° to the normal (because the first ray's 15° reflection sets the reference), the second ray reflects at 75°. 4. **Calculate the angle between the two reflected rays from M_2:** The two reflected rays from M_2 make angles of 15° and 75° with the normal to M_2. Therefore, the angle between them is: $$75^\circ - 15^\circ = 60^\circ$$ 5. **Answer:** The angle between the two rays reflected by M_2 is 60°. **Final answer: 60° (Option D).**