. Describe in brief how would you determine the approximate focal length of a convex lens


Describe in brief how would you determine the approximate focal length of a convex lens.

 

Best Answer

The approximate focal length of a convex lens can be determined by using the principle that a beam of parallel rays incident from a distant object is converged in the focal plane of the lens.

In an open space, against a white wall, a 0 cm end metre scale is placed horizontally touching the wall.

convex lens

By moving the convex lens to and fro along the length of the metre rule, focus the object on wall. The image formed on the wall is almost at the focus of the lens and from the image, the distance of the lens is read directly by the metre scale. This gives the approximate focal length of the lens.

 

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