Question

The steps followed in determining the focal length of a given convex lens by obtaining a sharp image of a distant object are listed below but they are not in correct order.]
(A) Measure the distance between the lens and screen
(B) Adjust the position of the lens to form a sharp image
(C) Select a suitable distant object
(D) Hold the lens between the object and the screen with its faces parallel to the screen.
What should be the correct sequence of steps ?

• A. C, A, D, B
• B. C, D, B, A
• C. C, A, B, D
• D. A, B, C, D

Answer 1

The correct option is B C, D, B, A

The correct sequence is below :

(C) Select a suitable distant object, distant object will be considered at infinity.

(D) Hold the lens between object and screen with its faces parallel to the screen, so that rays from object can be converged by lens on screen.

(B) Adjust the position of lens to form a sharp image on screen.

(A) Measure the distance between lens and screen, it will be the focal length of convex lens because image of an object at infinity is always formed on focus.