Question

A point source of light is placed in front of a plane mirror as shown in the fig. Determine the length of reflected path of light on the screen ($\sum$).

• A. $L$
• B. $2L$
• C. $\frac{3L}{2}$
• D. $\frac{L}{2}$

Answer 1

The correct option is C $\frac{3L}{2}$

The reflected rays will trace the green path as shown in the figure.
By similarity of triangles, we can deduce that the distance of the ray reflected from the top of the mirror will be $2L$ from the mirror.
Similarly, we can deduce that the distance of the ray reflected from the bottom of the mirror will be $\frac{L}{2}$ from the mirror.
So the length of the illuminated path will be $2L-\frac{L}{2}=\frac{3L}{2}$