Question

The image of a stationary person is formed by a plane mirror moving at ${60}^{\circ }$ to its normal. The speed of the image as seen by the person himself is

• A. Less than the speed of the mirror.
• B. More than the speed of the mirror.
  
• C. Equal to the speed of the mirror.
  
• D. Either $\left(A\right)$ or $\left(C\right)$ depending on the position of the person.
  

Answer 1

The correct option is C Equal to the speed of the mirror.


As we know that speed of mirror parallel to the mirror will not contribute to image speed.

Along perpendicular to the mirror,
Speed of image, $V_i=2V_m-V_o$

Here, speed of object, $V_o=0$

So, $V_i=2\times \frac{V}{2}=V$

Therefore, the speed of the image as seen by the person himself is equal to the speed of the mirror.