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Find the focal length of a lens of power -2.0 D. What type of lens is this?

Refraction Lens

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Answer

Given,

P = -2.0 D

f = ?

We know,

Power of lens (P) = 1focal length\dfrac{1}{\text{focal length}}

As the given power is negative hence, we can say that the lens used is concave in nature.

Substituting the value of power in formula we get,

-2 = 1f\dfrac{1}{\text{f}}

f = - 12\dfrac{1}{\text{2}}

f = -0.5 m

Therefore, focal length is -0.5 m and it is a concave lens.

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