Question

explain three special rays for lenses..​

Answer 1

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Three special rays for lenses are :-

i) An incident ray , parallel to principal axis, passes through (or appears to come from) , the (second) principal focus of the lens.

ii) An incident ray passing through the optical centre of the lens goes undeviated from the lens.

iii) An incident ray, passing through the first principal focus of the lens , or directed towards it , becomes parallel to the principal axis after refraction from the lens.