Question

Write its SI unit. A student uses a lens of focal length 40cm and another of -20 cm. Write the nature and power of each lens. ​

Answer 1

Here goes the answer.........

Answer 2

The si unit of power is dioptres

power=1/focal length(in metres)

=100/focal(in cms)

=100/40

=2.5D

the nature of this lens is converging ie convex lens

100/-20

-5D

the nature of this lens is diverging ie concave lens