Question.
Find the focal length of a lens of power $-2.0 \mathrm{D}$. What type of lens is this?
Find the focal length of a lens of power $-2.0 \mathrm{D}$. What type of lens is this?
solution:
Given, power, $P=-2.0$ D
Power, $P=\frac{1}{f}$
or $f=\frac{1}{P}=\frac{1}{-2}=-0.5 \mathrm{~m}=-50 \mathrm{~cm}$
The lens is a concave (or diverging) lens.
Given, power, $P=-2.0$ D
Power, $P=\frac{1}{f}$
or $f=\frac{1}{P}=\frac{1}{-2}=-0.5 \mathrm{~m}=-50 \mathrm{~cm}$
The lens is a concave (or diverging) lens.