Chapter 30, Problem 19A

Here Percy is in front of a diverging lens. Virtual images are seen by viewing from the right side of the lens. For object positions A, B, and C, rank the sizes of the virtual images from largest to smallest.

To determine

To rank: The image distance if object is moved away from the concave lens.

Explanation of Solution

Introduction:

A convex lens is also called diverging lens as it diverges all the beam of light incident on it to a single point called focus.

As a concave lens diverges the beam of light incident on it, if the object is placed farther from the lens, the image also moves farther from it. For example let’s consider two cases 1) when the object is at infinity, the image formed by the lens is at its focus 2) when the object is beyond focus, the image is formed between optical centre and focus.

These two examples clearly make it easy to understand that as the object is shifted towards the concave lens, it image shifts more towards the lens and is also formed magnified. In the same way, as the object is shifted away from the lens, its image also moves away from the lens and is smaller in size.

Conclusion:

Hence, based on the above facts, the image formed would be larger when the object is placed at A, then at B and largest at C.