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### To Find The Focal Length Of A Concave Lens Using A Convex Lens

To find the focal length of a concave lens using a convex lens.

We use the lens formula in this experiment to calculate the focal length of the concave lens:

From sign convention, the f obtained from the above formula will be negative as v > u and u – v is negative.

To determine the rough focal length of the convex lens

The rough focal length of a convex lens = ……….

The actual length of the knitting needle, x = ………

Observed distance between the concave lens and image = ……..

Needle when knitting needle is placed between them, y = ……..

Index correction for u as well as v, x – y = ……..

(Mean,f=frac{f_{1}+f_{2}+f_{3}}{3})

The focal length of the given concave lens = …….. cm

Ans: Spherical lens is defined as a lens that is part of a sphere and has a surface that is spherical.

Q2. What type of lens is present in human eye?

Ans: Convex lens is present in human eye.

Q3. What are the factors affecting the power of lens?

Ans: Following are the factors affecting the power of lens:

Q4. What is the focal length of a lens?

Ans: The focal length of a lens is defined as the distance between the optical centre and the principal focus of the lens.

Ans: Lenses are used in spectacles, microscopes, in optical instruments, and in telescopes.