Question

Two lenses are placed 34 cm apart. An object is placed 24 cm to the left of the first lens which is a diverging lens with a focal length f1 = -7 cm. If the second lens is converging with a focal length f2 = 13 cm

(a) find the distance from the first lens to the final image?

(b) find the magnification of the final image?

Answer 1

(a)
d = 34 cm
So1 = 24 cm
f1 = -7 cm
f2 = 13 cm

Find the first image formed:
1/So1 + 1/Si1 = 1/f1
Solve for Si1

Then, you can relate the first image as the second object using the relation:
So2 = d - Si1

Then solve for the final image distance from:
1/So2 + 1/Si2 = 1/f2
Solve for Si2

To find the distance to the final image from the FIRST lens, you simply add the distance between the lens.
Si2 with respect to the first lens = d + Si2

(b)
magnification is the product of the individual magnifications.
M = M1M2

M1 = -Si1/So1
M2 = -Si2/So2

M = (-Si1/So1)*(-Si2/So2)

Answer 2

Thanks