1.

The power of a concave lens is -2.5 dioptres. Find it focal length.Calculate the focal length of a corrective lens having power +2.5 D.

Answer»

Solution :DATA : Convex lens , `P=-2.5 D , F=?`
`P=1/ftherefore -2.5D=1/f`
`f=-1/(2.5D) = -0.4 m =-40CM`
The focal LENGTH of the lens = -40cm.


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