Question

define principal focus of spherical lens and spherical mirror

Answer 1

Hi ...
principal Focus of spherical mirror:- they light rays which are parallel to axis meet in which point of axis or appears to be meet .after reflection..that point is called principal Focus of. the spherical mirror.
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for lens...the light rays which are parallel to axis meet to a point or appears to be meet to a point on axis after refraction..that point is called principal Focus of lens