Formula of focal length in convex lens is

f = \frac{u + v}{u - v}

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f = \frac{u \times v}{u - v}

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f = \frac{u - v}{u + v}

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f = \frac{u + v}{u + v}

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Solution

The correct option is B $f = \frac{u \times v}{u - v}$
$\begin{matrix} Focal length of lens, from lens formula : \begin{matrix} \frac{1}{f} = \frac{1}{v} - \frac{1}{u} \frac{1}{f} = \frac{u - v}{v \times u} f = \frac{v \times u}{u - v} \end{matrix} \end{matrix}$

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Formula of focal length in convex lens is

The correct option is B f=u×vu−v Focal length of lens, from lens formula : 1f=1v−1u1f=u−vv×uf=v×uu−v

The correct option is B $f = \frac{u \times v}{u - v}$
$\begin{matrix} Focal length of lens, from lens formula : \begin{matrix} \frac{1}{f} = \frac{1}{v} - \frac{1}{u} \frac{1}{f} = \frac{u - v}{v \times u} f = \frac{v \times u}{u - v} \end{matrix} \end{matrix}$