8RB Group D 23-Sep-2018 Shift 1 Solved Paper

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Question : 12 of 100

Marks: +1, -0

The power of a lens is -2.5 D. The type of lens and its focal length are respectively:

Convex, -0.40 m
Concave, -0.40 m
Concave, 0.40 m
Convex, 0.40 m

Solution:

Power of a lens

(P)=-2.5 D

{P}=1 /

focal length

({f})

So,

{f}=1 / {P}

i.e.

1 /-2.5=-2 / 5

or

-0.40 {m}

Type of lens is Concave.

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