Question

what is the focal length of double concave lens kept in air with two spherical surface of radio R1=30cm and R2=60cm.Take refractive index of lens as n=1.5.​

Answer 1

Answer:

lens maker formula

1/f=(nl/nm-1)(1/r1-1/r2)

1/f=(0.5)(1/60-1/30)

1/f=1/2(-1/60)

f=-120