Question
The image of a small electric bulb fixed on the wall of a room is to be obtained on the opposite wall 3 m away by means of a large convex lens. What is the maximum possible focal length of the lens required for the purpose?
Solution
For a real image to be obtained on the wall, minimum distance between the object and image should be 4f.
That is,
4f = 3 m
is the maximum focal length of the lens required.
That is,
4f = 3 m
is the maximum focal length of the lens required.
