To determine the focal length of a convex lens by obtaining a sharp image of a distant object we generally follow the following steps which are not in proper sequence. (a) Hold the lens between the object and the screen (b) Measure the distance between the lens and the screen (c) Select a well lit distant object (d) Place a screen opposite to the object on the lab table (e) Adjust the position of the lens to form a sharp image. The correct sequence of these steps is :

The experiment is based on the principle that rays of light originating from a distant object (at infinity) are parallel to each other. When these parallel rays pass through a convex lens, they converge at its principal focus. Thus, a sharp image of the distant object is formed on a screen placed at the focal plane of the lens.

• Option B (c, d, a, e, b) is correct because it outlines the correct chronological order of setting up the source, placing the screen, inserting the lens, focusing the image, and measuring the distance.
• Options A, C, and D are incorrect because they suggest adjusting the lens or measuring distances before the screen is placed or the object is selected, which is experimentally incorrect.