Question

Radii of curvature of the faces of a double convex lens are 10 and 15.if focal length of lens is 12,find ri

Answer 1

Hey !!

Seems like your question is incomplete !!

Question : The Radii of curvature of the faces of a double convex lens are 10 and 15.if focal length of lens is 12, find the refractive index of the material of the lens.

Answer :- Given,

                   R₁ = 10 cm , R₂ = -15 cm , f = 12 cm        

 Lens Maker formula is

                     1/f = (n-1) (1/R₁ - 1/R₂)          

               1/12 = (n-1) (1/10 + 1/15)            

                  1/12 = (n-1) × 5/30          

                n-1 = 30/5 × 1/12

                = 0.5

      Refractive Index, n = 1 + 0.5 = 1.5        

Good luck !!