A ray Of light makes an angle of 10° with the horizontal and strikes a plane mirror which is inclined at an angle to the horizontal. The angle r for which reflected ray becomes vertical is what

Angle between the reflected and incident ray = 80 (Final ray is vertical and incidence is 10 wrt horizontal) Angle of incidence = angle of reflected ray = 40 Angle of reflected ray with mirror = 90 – 40 = 50 So, angle with horizontal = 90 – 50 = 40