Question

4. Obtain the formula for the focal length of a lens in terms of object distance (u) and magnification (m)

Answer 1

I hope this is your very helpful answer

Answer 2

Concept Introduction:

A expression containing mathematical symbols to solve numerical problems is known as Formula. All scientific equations are made by combining many formulas by the scientists.

Given:

We have been given a question in which we need to obtain a formula for the focal length of a lens in terms of object distance (u) and magnification (m).

To Find:

We have to find the proper solution to obtain the formula.

Solution:

According to the problem,

For a lens, 1/f = 1/v – 1/u

And, magnification, m = v/u

or,  v = mu

So,  1/f = 1/mu – 1/u

or,  1/f = (1/u)(1/m – 1)

or,  1/f = (1/u)(1 – m)/m

or,  f = mu/(1 – m)

Final Answer:

f = mu/(1 – m)

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