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?

Options

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

Answer

To determine the focal length of a given convex lens by obtaining a sharp image of a distant object, we need to follow these steps in the correct order:

1. **Select a suitable distant object (C)**: The first step is to choose an object that is far away. This is important because light rays coming from a distant object can be considered parallel when they reach the lens.

2. **Hold the lens between the object and the screen with its faces parallel to the screen (D)**: Next, we need to position the lens correctly. The lens should be held between the distant object and the screen, ensuring that its faces are parallel to the screen. This alignment is crucial for proper image formation.

3. **Adjust the position of the lens to form a sharp image (B)**: After placing the lens, we need to adjust its position slightly to ensure that the image formed on the screen is sharp and clear. This may involve moving the lens closer to or further away from the screen until the image is focused.

4. **Measure the distance between the lens and screen (A)**: Finally, we measure the distance from the lens to the screen. This distance (denoted as 'v') is equal to the focal length of the lens when the object is at a considerable distance, as the rays from the distant object are parallel.

Thus, the correct sequence of steps is: **C → D → B → A**.

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