Question

Figure shows two plane mirrors and an object $\text{O}$ placed between them. What will be distance of the first three images from the mirror $M_2$?

• A. $2\text{cm}$, $12\text{cm}$, $18\text{cm}$
• B. $2\text{cm}$, $8\text{cm}$, $12\text{cm}$
• C. $2\text{cm}$, $18\text{cm}$, $22\text{cm}$
• D. $2\text{cm}$, $24\text{cm}$, $38\text{cm}$

Answer 1

The correct option is C $2\text{cm}$, $18\text{cm}$, $22\text{cm}$


Here, in the figure first three images formed in $M_2$ are $I_2$, $I_{12}$ and $I_{21/2}$.

Object distance for image, $I_2$ is $2\text{cm}$,
So, the image formed at distance $2\text{cm}$ left from $M_2$.

Now, $I_1$ is the object for the image $I_{12}$, which is at distance $(8+8+2=18\text{cm})$ right from $M_2$.

So, the image distance would be $18\text{cm}$ left from $M_2$.

Similarly,
$I_{21}$ is the object for the image $I_{21/2}$ which is at distance $(12+8+2=22\text{cm})$ from $M_2$.
So, the image distance would be $22\text{cm}$ from $M_2$.

Hence, option (c) is the correct option.

Why this Question: To understand the number of images formed by parallel plane mirrors.