Question

Paragraph : Two plane mirrors kept at an angle ${90}^{\circ }$, as shown in the figure. It is obvious that $M_1$ will form an image of point object O, and $M_2$ will form an image of it. But in practical scenario, a third image is also seen.


The third image formed is :

• A. The image of $I_1$, in $M_2$.
  
• B. The image of $I_2$, in $M_1$.
• C. The image of $I_1$, in $M_1$.
• D. The image of $I_2$, in $M_2$.

Answer 1

Answer: (A), (B)

The image of $I_2$, in $M_1$.

Now as we have seen that $I_1$ served as an object for $M_2$, or in other words : "light rays coming from $I_1$, fall on $M_2$", these rays will get reflected from $M_2$ and the extrapolation of these reflected rays will give us "the image of $I_1$, in $M_2$"

we can also say that, $I_2$ served as an object for $M_1$, or in other words : "light rays coming from $I_2$, fall on $M_1$", these rays will get reflected from $M_1$ and the extrapolation of these reflected rays will give us "the image of $I_2$, in $M_1$".
It must be the same point where we have $I_3$.
There are two reasons for it :
1.We don’t have a fourth image
2.Symmetry