Question

An astronomical telescope has objective and eye-piece lenses of powers 0.5 d and 20 d respectively. What will be its magnifying power

Answer 1

for normal adjustment
m= -fo/fe
1/fo= o.5
1/fe= 20

so put the ratio for fo/fe
you will get
for/fe= 1/0.5 //1/20
=20/0.5 = 40