Q187 / 200 · Manipal (MET) 2012 · Physics
A ray reflected successively from two plane mirrors inclined at a certain angle undergoes a deviation of $240^{\circ}$. Then, the number of images observable is
- A3
- Correct answerB5
- C7
- D9
Solution
$\begin{aligned}
& D=360^{\circ}-2 \theta \Rightarrow 240^{\circ}=360^{\circ}-2 \theta \\
& 2 \theta=120^{\circ}, \quad \therefore \quad \theta=60^{\circ}
\end{aligned}$
Then, number of images observable
$\begin{aligned}
& N=\frac{360^{\circ}}{60^{\circ}}-1 \\
& N=6-1 \\
& N=5
\end{aligned}$
Hence, the correct answer is option: 'B'.