When two thin lenses of focal lengths fi and f, are kept coaxially and in contact, prove that their cobined focal length "f" is given by :
`(1)/(f)=(1)/(f_(1))+(1)/(f_(2))`

Explanation

To prove that the combined focal length \( f \) of two thin lenses in contact with focal lengths \( f_1 \) and \( f_2 \) is given by the formula:

\[ \frac{1}{f} = \frac{1}{f_1} + \frac{1}{f_2} \]

we will follow these steps:

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