Question

Assertion: If the angle between the two plane mirrors is ${72}^{\circ }$ and the object is asymmetrically placed between the two mirrors, then $5$ images of the object will be formed.
Reason: For a given system of mirrors, the total number of images formed due to successive reflection of an asymmetrically placed object is equal to either $\frac{{360}^{\circ }}{\theta }$ or $\frac{{360}^{\circ }}{\theta }-1$ accordingly as $\frac{{360}^{\circ }}{\theta }$ is odd or even respectively.

• A. Both assertion and reason are correct and reason is the correct explanation of assertion.
• B. Both assertion and reason are correct and reason is not the correct explanation of assertion.
• C. Assertion is correct, but reason is incorrect.
• D. Both assertion and reason are incorrect.

Answer 1

The correct option is A Both assertion and reason are correct and reason is the correct explanation of assertion.


For asymmetric placement of the object between the two plane mirrors inlined at some angle $\theta$, the number of images formed will be,
$\frac{{360}^{\circ }}{\theta }-1$, when $\frac{{360}^{\circ }}{\theta }$ is even
$\frac{{360}^{\circ }}{\theta }$, when $\frac{{360}^{\circ }}{\theta }$ is odd

Here, $n=\frac{{360}^{\circ }}{\theta }=\frac{{360}^{\circ }}{{72}^{\circ }}=5$
As $n$ is odd and the object is placed asymmetrically,
$\therefore$ Number of images $=5$
Both assertion and reason are correct and reason is the correct explanation of assertion.