1.

Which of the following statement is true ?

Answer»

<P>A convex lens has 4 D POWER having a FOCAL LENGTH + 0.25 m
A convex lens has -4 D power having a focal length -0.25 m
A concave lens has 4 D power having a focal length + 0.25 m
A concave lens has -4 D power having a focal length + 0.25 m

Solution :Focal length of a convex lens is +ve (0.25 m) and so it power `P = (1)/(f) = + (1)/(0.25) = +4` D


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