A 39.5-cm-focal-length converging lens is 28.0 cm behind a diverging lens. Parallel light strikes the diverging lens. After passing through the converging lens, the light is again parallel.

What is the focal length of the diverging lens?

Focal length = 11.5 cm

Explanation:

The rays diverge at the focus of the converging lens because the source of the parallel rays should be at the focus of the converging lens for parallel rays that will strike the diverging lens to originate from it.

Therefore, the focal length of the diverging lens, f = 39.5 - 28

f = 11.5 cm