Question

Why is convex lens of small focal length preferred for a magnifying glass .? ​

Answer 1

Magnifying glasses are used to get an enlarged image of a nearby object. So using one with larger focal length is not applicable as the object should be placed at larger distance. So those magnifying glasses with smaller focal length are preferred.

Answer 2

Answer:

The Convex lens with a comparatively smaller focal length is preferred in magnifying glasses because shorter focal lengths produce more clear and magnified images which are of great power.

Explanation:

What is Focal Length?

In a lens, the focal length is described as the distance between the focus of the lens and the centre of the lens. Any object placed between focus and the centre of the lens will have a magnified image of it.

If a lens is really curvy and has a small focal length, this means the power of image it produces would be great as Power ∝ $\frac{1}{focal \\ length}$. Hence the image produced would be clear and therefore, small focal length is preferred.