. Define the term principal foci of a concave lens and show them with the help of proper diagrams


Define the term principal foci of a concave lens and show them with the help of proper diagrams.

 

Best Answer

A light ray can pass through a lens from either side. Hence, a lens has two principal foci.

For a concave lens, the first focal point is a point F1 on the principal axis of a lens such that the incident rays of light appearing to meet at it, after refraction from the lens become parallel to the principal axis of the lens.

concave lens

For a concave lens, the second focal point is a point F2 on the principal axis of the lens such that the rays of light incident parallel to the principal axis, after refraction from the lens, appear to be diverging from this point.

concave lens

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