Two point light sources are 24cm apart. At what distance from one source must a convex lens of focal length 9cm be kept in between them so that the images of both the sources are formed at the same place?

Explanation

The problem involves placing a convex lens of focal length 9cm between two point light sources that are 24cm apart such that the images of both sources are formed at the same place. To achieve this, you need to place the lens in such a way that the lens equation 1/f = 1/u + 1/v is satisfied for both sources, where u is the object distance and v is the image distance. For the images to coincide, the distance from the lens to each source must be adjusted such that the images fall at the same point. Calculating using the lens formula, the correct placement is 12cm from one source, making the distances from the lens to the sources 12cm and 12cm, respectively. This placement allows for the correct focal alignment. The other options do not satisfy the lens equation for both sources to have images at the same location.