Question

An object is placed 20.0 cm to the left of a convex lens with a focal length of +8.0 cm. Where is the image of the object?

28 cm to the left of the lens

28 cm to the right of the lens

13 cm to the left of the lens

13 cm to the right of the lens

Answer 1

v = image distance
m = magnification
Real is Positive sign convention.

Converging Lens:
1 / 20 + 1 / v = 1 / 25
v = - 100 cm.
m = - 100 / 20 = - 5.0
Virtual image 100 cm. left of the converging lens.
Magnification 5.0.

Virtual image becomes a real object 125 cm. left of the diverging lens.
1 / 125 + 1 / v = - 1 / 10
v = - 9.3 cm.
m = - 9.3 / 125
Virtual image 9.3 cm. left of the diverging lens.
Magnification = 5.0 * 9.3 / 125
= 0.370.