Question

A student uses a lens of focal length 40cm and

another -20 cm write the nature and power of lens

Answer 1

let take lens1 as focal of 40 and lens2 of focal length of- 20 cm and p1 as power of lens1 and p2 as power of lens2
positive sign of lens1 represent it is a convex lens . hence, it is real and invert
similarly lens2 is virtual and erect

p1=100/f (for cm)
p1=2.5D
p2=100/f (for cm)
p2=-5.0D

please mark this as brainliest answer

Answer 2

Power of lens (P) = 1/f
So, power of first lens = 1/0.4m (4cm)
= 2.5 Dioptre

Now, power of second lens = 1/-0.2m (2cm)
= -5 Dioptre.

First lens is a convex lens because its power is positive.
Second lens is a concave lens because its power is negative.

:D