Question

Why does a large radius of curvature give a large focal point and why does a small radius give a small focal? Using Snell's law to explain.

Why do light rays that strike the edge of the lens bend more than light rays that strike the center? Using Snell's Law and the behavior of Principal Rays to explain.

Answer 1

Snells law is given by n1sin(theta 1) = n2sin(theta2).

The focal point is the point where all the rays are concentrated at a point. For , len e having large radius is possible to concentrate more rays at point . And lens having small radius can concentrate small amount of rays at point. Hence, larger radius have large focal point than the small radius of curvature.

According to the snells law, sin(0) gives zero. Henc, the ray at th center of the lens can travel straight without bending. But, when the rays travel edge of th Lense according to the law it will bend because it should concentrate at point. So, the rays will bend at the edges more than the center.