Question

find the focal length and double convex lens has two surfaces equal radii R and refractive index n = 15

Answer 1

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

n=1.5

R1=R2=R

1/f=(1.5-1)(1/R+1/R)

1/f=(0.5)(1+1/R)

1/f=1/2(2/R)

1/f=1/R

f=R