Question

The bulb used in a torch light is placed at a distance $x$ from the mirror used. The value of $x$ is

• A. $f/2$
• B. $f$
• C. $f/3$
• D. $3f$

Answer 1

The correct option is B

$f$

1. When the object is placed at the focus point, the image forms at infinity, as all the light rays become parallel to the principal axis, which is useful in a torch.
2. Thus, the bulb used in a torch must be placed at the focus point of the mirror used so that its light spreads to a long distance.

Final answer - Hence, option (b) is the correct answer.