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Question:

Which of the following lenses would you prefer to use while reading small letters found in a dictionary?

A convex lens of focal length 5 cm

A concave lens of focal length 5 cm

A concave lens of focal length 50 cm

A convex lens of focal length 50 cm

Solution:

A convex lens is also used as a simple microscope. The object is kept between the focal length and mirror so that a virtual, erect and magnified image is formed. Smaller focal length has more power and is suitable for larger magnification. Hence, convex lens of focal length 5 cm is preferred.