A converging light beam incidents on diverging lens. After passing through lens, rays intersect at 15 cm behind the lens. If lens is kept away, then these rays intersect at 5 cm. Focal length of lens is ..

A converging light beam incidents on diverging lens. After passing thr

1.	A converging light beam incidents on diverging lens. After passing through lens, rays intersect at 15 cm behind the lens. If lens is kept away, then these rays intersect at 5 cm. Focal length of lens is ..
Answer» `-10 cm` 20 cm `-30` cm 5 cm Solution : ACCORDING to lens equation, `1/v-1/u=1/f` u=-10 cm , v=15 cm ,f=(?) `(1)/(15)-(1)/(10)=1/f` `thereforef=-(150)/(3)` `thereforef=-30` cm

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A converging light beam incidents on diverging lens. After passing through lens, rays intersect at 15 cm behind the lens. If lens is kept away, then these rays intersect at 5 cm. Focal length of lens is ..

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