. 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

Best Answer

Correct option is: (A)

Explanation:

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 lens.

Final Answer:

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.

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