1.

A convex lens if in contact with concave lens. The magnitude of the ratio of their focal length is `(2)/(3)`. Their equivalent focal length is 30 cm. What are their individual focal lengths?A. `-75,50`B. `-10,15`C. `75,50`D. `-15,10`

Answer» Correct Answer - D
`(f_(1))/(f_(2))=(2)/(3)` ....(i)
`(1)/(f_(1))-(1)/(f_(2))=(1)/(30)` ....(ii)
Solving equations `(i)` and `(ii)`
`f_(2)=-15cm` `(` Concave`) `
`f_(1)=10 cm` `(` Convex `)`


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