a) Find the focal length of this lens?
b) Find optical power of the lens?
Using lensmaker’s equation
Following the sign convention for spherical refracting surfaces, we have
Convex: R1 = + 8 cm
Concave: R2 = - 8 cm
Using these values for radii and n = 1.5 for the index of refraction, we can find focal length for this lens
f = 8 cm
Focal length of the lens is 8 cm.
The optical power P of a lens is defined as the inverse of its focal length.
P = 12.5 d
Optical power of the lens is 12.5 d.