Question

A converging lens with a focal length of 40 cm and a diverging lens with a focal length of -68 cm are 188 cm apart. A 3.1-cm-tall object is 60 cm in front of the converging lens.

Calculate the distance between image and diverging lens.

Calculate the image height.

Answer 1

  f1 = 40 cm
f2 = -68 cm
x = 188 cm
ho =3.1 cm
do1 = 60 cm

for the converging lens :
di1 = ( do1 * f)/( do1 - f)
= (60 * 40)/( 60 - 40) = 120 cm
for the diverging lens :
do = x - di1 = 188 - 120 = 68cm

di2 = ( do2 * f)/( do2 - f)
= (68 * (-68))/( 68 - (-68)) = -34 cm ( front of the diverging lens)

M = di1/do1 * di2/do2
h''/1 = (120/60) * (34/68)
h'' =1.0 cm