Which of the following is not correct with respect to all the spherical mirrors.

1. The pole lies on the principal axis.

2. Focal length is half of the radius of curvature.

3. Both virtual and real images can be formed by them.

4. Light rays moving towards or passing through the center of curvature retraces their path after reflection.

The correct option is A

The pole lies on the principal axis.

Correct option is A: The pole lies on the principal axis.

Explanation of correct option:

1. Option A: The pole in the spherical mirror lies on the surface of the mirror. Hence, the statement is wrong and option is correct according to question.

Explanation of incorrect option:

1. Option B: Focal length is half of the radius of curvature $R=2f$
2. Option C:Both virtual and real images can be formed by a concave mirror which is a type of spherical mirror.
3. Option D:In spherical mirror light rays moving towards or passing through the center of curvature retraces their path after reflection.

Final Answer: Option A