1.

The image of a small electric bulb fixed on the wall of a room is to be obtained on the opposite wall 3m away by means of a large convex lens. What is the maximum possible focal length of the lens required for the purpose?

Answer»

SOLUTION :For fixed distance s between object and screen, the lens EQUATION does not give a real solution for u or v if f is GREATER than s/4. THEREFORE, fmax = 0.75 m.
Therefore, `f_("max")=0.75m`.


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