Question

if a convex lens of focal length 80 cm and a concave lens of focal length 50 centimetre are combined together what will be the resulting power

Answer 1

p= 1/f in meter
threrefore p1 = 100/80 and p2 = -100/50 = -2(since focal length of concave lens is negative)
p1= 10/8 = 5/4
now resulting power = p1+p2 = 5/4+(-2) = 1.25-2=.75 diopter