NEET2009PhysicsRay OpticsActual

A convex lens of refractive index 3 2 has a power of 2.5 D in air. If it is placed in a liquid of refractive index 2 , then the new power of the lens is

Options

A-1.25 D
B-1.5 D
C1.25 D
D1.5 D

Correct answer

A. -1.25 D

Step-by-step solution

Focal length of a convex lens having power 2.5 D ,= 1 2.5 ~m Also focal length of a lens in a medium of refractive index is given by 1 f =( -1) ( 1 R₁ - 1 R₂ ) Dividing the two, 2.5 0.5 -0.25 1 f^ = -5 25 0.25 =-1.25 D

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