derive the relation between 1st principal focal length and 2nd principal focal length
Answers
Answer:
First principal focus: It is a point on the principal axis of the lens such that the rays of light starting from that point in case of a convex lens becomes parallel after refraction and in case of a concave lens a parallel beam of light appear to meet at that point after refraction.
Second principal focus: It is a point on the principal axis of the lens such that rays of light parallel to the principal axis meet at this point after refraction in the case of a convex lens and in the case of a concave lens the rays of light coming towards this focus becomes parallel after refraction.
Answer:
The distance from the pole to the focal point is called the focal length (f). The focal length of a spherical mirror is then approximately half its radius of curvature. It is important to note up front that this is an approximately true relationship.