Difference between Focus and principle Focus

1.	Difference between Focus and principle Focus
Answer» Principal focus is a point on the principal axis where the rays which are incident parallel to the principal axis meet after reflection.\xa0Principal focus is a point on focal plane and is located on the principal axis.Focus is a point where rays parallel to each other meet. It is not necessary for the rays to be parallel to the principal axis.These are infinite foci, all lying in a plane called focal plane. Very good question u put up https://youtu.be/1xKSSckSA0Q

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