Question

what is the focal length of double cancave lens kept in air with two sphercial surfaces of radii r1=30 and r2=60 cm take refractive index of lens n=15​

Answer 1

Answer:

R1=-30,R2=60,and also given lens is

in air so n=1.5

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

1/f=(1.5-1)[1/(-30)-1/60]

After solving

F=-40

hope it's help u.....