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Agnit Chatterjee

A convex lens of focal length f is placed somewhere in between an object and a screen. The distance between the object and the screen is x. If the numerical value of the magnification produced by the lens is m, the focal length of the lens will be

a) (mx)/[(m+1)^2] b) (mx)/[(m-1)^2]

c)[(m+1)^2]x/m d)[(m-1)^2]x/m

Krishna Gopal Singh

That means u = -x/(1+m) and v = mx/(1+m)

Now use lens formula to solve for focal length of lens

Agnit Chatterjee

Sir, how are you getting u = -x/(1+m) and v = mx/(1+m). Pls explain!!

ashwani kumar

As distance b/w object and screen is x it means disstance b/w object and image is x.

Use these two equations and solve
v + u =x
v/u =m
Now find u and v in terms of x and m , then solve by using lens formula.

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