Two plane mirrors and face each other and are apart

MATHEMATICS · Single correct · CBSE · Mathematics · Arithmetic Progressions · Arithmetic Progressions

Problem

Two plane mirrors

\mathbf{M_1}

and

\mathbf{M_2}

face each other and are

40\,\text{cm}

apart. A short light pulse enters the space between them and strikes mirror

\mathbf{M_1}

normally. The pulse then keeps bouncing back and forth between the mirrors. How much distance will the pulse cover by the time it strikes mirror

\mathbf{M_1}

for the fifth time (counting the first strike as the first)? (a)

2.00\,\text{m}

(b)

1.60\,\text{m}

(c)

0.80\,\text{m}

(d)

3.20\,\text{m}