Question

A converging bundle of rays is intercepted by a biconcave lens. The radii of curvature of both surfaces are 20cm and the refractive index of the material of the lens is 1.5. If the rays originially converged to a point 10cm in front of the lens, where will they now converge after passing through the lens?

Answer 1

Here, `mu=1.5, R_(1)=-20cm,` and `R_(2)=+20cm`.
Substituting in equation, we get `f=-20cm`
Now, `u=+10cm , f=-20cm`
Substituting in eqution, we get
`(1)/(v)=(1)/(-20)+(1)/(10)` or `v=+20cm`
Thus, the rays now converge to a point 20cm in front of the lens.