Question

Two converging lenses with focal lengths f and 2f are positioned at a distance 3f apart. A parallel beam of light is incident on the lens with focal length f. If d is the incident beam width, what is the width of the emerging beam?

Answer 1

Answer:

Width of output ray would be 2d

Explanation:

In order to completely understand the solution, kindly see the attached image. If we look at the image, if the incident light is made from the smaller lens of width d, then it will first converge and then eventually will move out of the bigger lens with double the diameter because the second lens is placed at 2f of the distance