Question

A student uses a lens of focal length 40 cm and another of -20 cm write the nature and power of each lens
​

Answer 1

Hey buddy.....here's your answer

Focal length of lens 1=40cm

The lens is convex lens.So,the nature of the image is real and inverted.

Power 1=P1=1/f1=1/40=0.025D

Focal length of lens 2= -20cm

The lens is concave lens.So,the nature of the image is virtual and erect.

Power 2=P2=1/f2=1/-20= -0.05D

I hope this will be helpful