Question

The magnification produced by a concave mirror of focal length 10 cm is positive, if the value of object distance is:

• A. more than 10 cm
• B. more than 20 cm
• C. less than 10 cm
• D. none of these

Hint:

For concave mirrors, virtual and erect images are formed when the object is placed within the focal length.

Answer 1

The Correct Option is C

The magnification of a mirror is given by:
\[ m = \frac{-v}{u} \] For concave mirrors, magnification is positive when the image is virtual and erect. This happens when the object is placed between the focus and the pole of the mirror, i.e., when \( u<10 \) cm.
Thus, the correct answer is \( \mathbf{(C) \text{less than 10 cm}} \).