Q. It is necessary to illuminate the bottom of a well by reflected solar beam when the light is incident at an angle of $\alpha = 40{^\circ}\ $to the vertical. At what angle $\beta\ $to the horizontal should a plane mirror be placed?
A) $70{^\circ}$
B) $20{^\circ}$
C) $50{^\circ}$
D) $40{^\circ}$
Explanation
(a) Clearly, $i + r = i + i = 140{^\circ}$
Or $i = 70{^\circ}$
[image:9_image76.emf]
Clearly, plane mirror makes as angle of $20{^\circ}$ with vertical and $70{^\circ}$ with horizontal
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.