Question

Two glasses with refractive indices of 1.5 and 1.7 are used to make two identical double convex lens. find the ratio of their focal lengths

Answer 1

Answer..
1/fa =(1.5 - 1)(1/R1 - 1/R2) ----(1)
1/fb =(1.7 - 1)(1/R1 - 1/R2) -----(2)

On dividing (2) by (1)
we get
fa/fb = 7/5

Thanks..