Question

A diverging lens with a focal length of -13 cm is placed 12 cm to the right of a converging lens with a focal length of 19 cm . An object is placed 31 cm to the left of the converging lens.

A.Where will the image be if the diverging lens is 39 cm from the converging lens?

Express your answer using two significant figures. di = ? cm from the diverging lens

Answer 1

here,

for the first lens ,

the object distance , d01 = 31 cm

focal length , f1 = - 13 cm

let the image distance be di1

using the lens formula

1/f1 = 1/di1 + 1/do1

- 1/13 = 1/di1 + 1/31

di1 = - 9.16 cm

for the seccond lens

the object distance , d02 = 39 - (-di1) = 48.16 cm

focal length , f2 = 19 cm

let the image distance be di2

using the lens formula

1/f2 = 1/di2 + 1/do2

1/19 = 1/di1 + 1/48.16

di2 = 31.4 cm

the final image distance is 31.4 cm

the distance from diverging lens = 31.4 + 31 cm = 62.4 cm