Question

what do you mean by principal focous​

Answer 1

Answer:

principal focus

The first principal focus of a lens is the position of the object on the principal axis of the lens, for which the image is formed at infinity. ... The distance of the first principal axis from the centre of the lens is known as the first principle focal length.

Answer 2

Answer:

Focus is the point where light rays originating from a point on the object converge. The principal focus is defined as the point where a beam parallel to the principal axis appears to diverge converges from a point on the principal axis after passing through the lens.

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