Question

Q - 1. (a) Find the focal length of a lens of power -2.0
D. what type of
lens is this?
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Answer 1

Answer:

Power = 1

focal length

$- 2.0 = \frac{1}{f}$

$f = \frac{ - 1}{2.0}$

$f = - 5 \: m$

This lens has a negative focal length i.e concave lens.

Answer 2

Power of lens (P) = 1/f

P = -2D

f = -1/2 = -0.5 m

A concave lens has a negative focal length. Therefore, it is a concave lens.