Q. A boy 1.5 m tall with his eye level at 1.38 m stands before a mirror fixed on a wall. The minimum length of mirror required to view the complete image of boy is
A) 0.75 m
B) 0.06 m
C) 0.69 m
D) 0.12 m
Explanation
(a) From the figure, it is clear that eye is at 1.38 m from the foot. Rays from foot can enter eye after reflection at $M_{2}$, whose height from ground
[image:9_image126.emf]
Again, eye is at 1.5 – 1.38 = 0.12 m from heat. Rays from head can enter eye after reflection at $M_{1}$, whose height above eye is
$\frac{0.12}{2} = 0.06\ m$
$\therefore$ Minimum length of mirror
= 0.69 + 0.06 = 0.75 m
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.