Question

Since a divergent lens cannot form a real image, how did you measure the focal length of the diverging lens? Explain the process in detail and in your own words.

Answer 1

A diverging lens always forms a virtual image for real object and a real image for a virtual object.

so, we place converging lens infront of object to get a real image.

now we place the diverging lens behind the converging lens.

now the real image of converging lens acts as virtual object for the diverging lens. Then the diverging lens forma a real image.

now by using the formula, 1/f = 1/u + 1/v

f ---> focal length of the diverging lens

u---> object distance(distance from the real formed by the converginglens to diverging lens)

v ---> image distance (distance between diverging lens to final real image fomred by divergin lens)