Which of the following lenses would you prefer to use while reading small letters found in a dictionary?
(a) A convex lens of focal length 50 cm.
(b) A concave lens of focal length 50 cm.
(c) A convex lens of focal length 5 cm.
(d) A concave lens of focal length 5 cm.

AcademicPhysicsNCERTClass 10

The correct answer is $(c)$. A convex lens of focal length 5 cm.

Explanation:

Letters found in the dictionary are too small to read. For magnification, a lens can be used as a lens that will help to read small letters found in the dictionary.

Choosing the right lens:

A convex lens will be preferred for reading small letters found in the dictionary as compared to a concave lens.

A convex lens of a focal length of 5 cm will be preferred because a convex lens of a shorter focal length gives more magnification which makes it easy to read small letters found in the dictionary. When an object is placed between the radius of curvature of a convex lens and its focal length, its magnified image is obtained.

Therefore, a convex lens of the focal length of $5\ cm$ will be preferable for reading small letters in a dictionary. 

A concave lens can't be used for reading too small letters found in a dictionary as it gives a diminished image.

So, option $(c)$ is correct. 

raja
Updated on 10-Oct-2022 13:20:02

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