Question

Two mirrors at an angle $\theta$ produce 5 images of a point. The number of images produced when $\theta$ is decreased to $\theta -30$ is

• A. $9$
• B. $10$
• C. $11$
• D. $12$

Answer 1

The correct option is C $11$

Number of images=$\frac{360}{\theta }-1$

$⟹\frac{360}{\theta }-1=5\therefore \theta =60°$

If now, $\theta =30°$

then, the number of images=$\frac{360}{\theta }-1=\frac{360}{{30}^{\circ }}=12-1=11$