Question

Two converging lenses are placed together with the focal lengths 15 cm and 30 cm respectively. Calculate the total power. ​

Answer 1

Explanation:

F1 = 15cm, f2 = 30cm

Focal length of combination,

1/f=1/f1+1/f2

1/f= 1/15+1/30

1/f= (15+30)/(15*30)

f = 450/45

f= 10cm

4.0

Answer 2

Answer:

Explanation:

COMBINED FOCAL LENGTH F OF TWO LENSES OF FOCAL LENGTHS f 1 AND f 2 is given by

1/F = 1/f 1 + 1/f 2

F = f 1 *f 2 /f 1+ f 2

if f 1= 15 cm  and f 2 = 30 cm then we get F 10 cm

hence power = 100 /10 = 10 D