A thin equi-convex lens having radius of curvature 10cm is placed as shown in figure . Calculate the focal length of the lens, if parallel rays are incident as shown

A thin equi-convex lens having radius of curvature 10cm is placed as s

1.	A thin equi-convex lens having radius of curvature 10cm is placed as shown in figure . Calculate the focal length of the lens, if parallel rays are incident as shown
Answer» Solution :Refraction at 1st SURFACE `u=infty, mu_1=5/4 mu_2=5/3` `mu_2/v-mu_1/u=(mu_2-mu_1)/R_1 implies 5/(3v)=(5/3-5/4)/10 implies v=40cm` Refraction at SECOND surface `mu_1=5/3,mu_2=3/2 mu=+40 v=? R=-10` `3/(2v)-5/(3 times 40)=(3/2-5/3)/(-10)` After solving we get `V=180/7 cm` So FOCAL LENGTH `=180/7 cm`