Question

What is principal focus for concave lens?

• A. It is a point on the principal axis of a concave lens from which a parallel beam of light rays, travelling parallel to the principal axis, appears to come after passing through the lens.
• B. It is a point on the principal axis of a concave lens from which a perpendicular beam of light rays, travelling perpendicular to the principal axis, appears to come after passing through the lens.
• C. It is a point on the principal axis of a convex lens at which a parallel beam of light rays, travelling parallel to principal axis, meet after passing through the lens.
• D. None

Answer 1

Answer: (A)

It is a point on the principal axis of a concave lens from which a parallel beam of light rays, travelling parallel to the principal axis, appears to come after passing through the lens.

Correct answer is (a)

Principal focus is a point on the principal axis of a concave lens from which a parallel beam of light rays, travelling parallel to the principal axis appears to come after passing through the concave lens.