Question

A lens has a power of -0.25D. What is focal length and type of the lens? *

1)f = -25 m, Concave lens
2)f = -4 m, Concave mirror
3)f = -25 m, Convex lens
4)f = -4 m, Concave lens

Answer 1

Answer:

2)f = -4 m, Concave mirror

Explanation:

We know that power of lens is P=

f

1

P=-25D

So −25=

f

1

f=−.04m=−4cm

The power of this lens has minus sign, so it is a concave lens.

Answer 2

Answer:

2.)

is correct answer

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