When an object is kept at a distance 20 cm in front of a concave mirror, a real image is formed at the centre of curvature of the mirror. Magnification produced by the mirror is ___________.

Correct option is B

The correct answer is (B) -1.

Explanation:

The magnification (M) of a mirror is given by:

​$$M=\frac{-v}{u}$$​​

Where:

• v = Image distance,
• u = Object distance.

Given:

• Object distance, u=−20 cm (negative because the object is in front of the mirror),
• Image distance, v=−20 cm (negative because a real image is formed at the center of curvature).

Now calculate magnification:

​$$M=\frac{-v}{u} = \frac{-(-20)}{-20} = -1$$​​

Interpretation:

• Magnification M=−1 indicates the image is real, inverted, and of the same size as the object.