Question

a double concave lens with the refractive index (n)=1.5 is kept in the air its two spherical surfaces have radii R1=20cm and R2= 60cm . find the focal length of the lens.write the characteristics of the lens

Answer 1

we can apply lens maker formula..
1/f = (n-1)(1/R1 - 1/R2)
1/f = (1.5-1)(1/20-1/60)
1/f = (0.5)(2/60)
1/f = (0.5)(1/30)
f= 60cm
hope it helped u...