Question

Focal plane of a spherical mirror is

• A. Line joining pole (P) and focus (F) of the mirror
• B. Plane perpendicular to the principal axis at focus (F)
• C. Plane perpendicular at centre of curvature (C)
• D. Plane parallel to the principal axis.

Answer 1

The Correct Option is B

To solve the problem, we need to determine the correct definition of the focal plane of a spherical mirror.

1. Understanding the Focal Plane:
The focal plane of a spherical mirror is defined as the plane that passes through the focus (F) and is perpendicular to the principal axis.

2. Evaluate the Given Options:
- Option (A): Line joining P and F – This is the principal axis, not the focal plane.
- Option (B): Plane perpendicular to the principal axis at focus (F) – This is the correct definition of the focal plane.
- Option (C): Plane perpendicular at centre of curvature – This is not the definition of the focal plane.
- Option (D): Plane parallel to the principal axis – Also incorrect.

Final Answer:
The correct answer is option (B): Plane perpendicular to the principal axis at focus (F).