Task id16610

Task id16610

A collecting lens moves between the luminous object and the screen, located at a distance L = 120 cm from each other. At a certain position of the lens on the screen, a clear magnified image of the object is obtained. When the lens moves l = 90 cm, a clear reduced image of the object is obtained on the screen. Find the focal length of the lens.

Additional information:

Detailed solution. Format gif