Two thin lenses with 15.0-cm focal lengths at are mounted at opposite ends of a 60.0-cm long tube.An object is located 66.0 cm from one end of the tube.How far from the opposite end is the final image?

Question

Quizplus · Accepted Answer

Using the thin lens equation, we can find the image distance for the first lens:
1/f = 1/o + 1/i1
1/15 = 1/66 + 1/i1
i1 = 22.5 cm

The image from the first lens acts as the object for the second lens:
1/f = 1/o + 1/i2
1/15 = 1/37.5 + 1/i2
i2 = 23.8 cm

Therefore, the final image is located 23.8 cm from the opposite end of the tube.

Two Thin Lenses with 15