Question

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

Answer 1

nature is concave lens

by power formula..

power =1/f

= 1 /0.4

2.5 D

for second lens.. focal lenght

= -20cm

=-0.2m

1/f =1/0.2 =5D