Question

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 a practical scenario, a third image is also seen. Answer the following questions based on this situation :

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 correct options are
A

The image of $I_1$, in $M_2$

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