Question

what is meant by power of lens define its SI unit you have two lenses A and B of focal lengths positive 10 centimetre negative 10 centimetre respectively state the nature and power of each lens .which of the two lenses will form virtual and magnified image of an object placed 8 cm from the lens?draw a ray diagram to justify your answer​

Answer 1

Power of lenses

converge or diverge the rays In lens

or another definition in ncert textbook.

Reciprocal of its focal length.

Lens A

+10 =f

so, Convex lens ,real and inverted, Enlarged.

p=1/f

p=100/10cm

=10 Dioptre

Lens B

-10 =f

so Concave lens,

virtual and erect

Diminished.

P=-100/10

P=-10 D

next question,

Case 1 , convex case 2

f=10 u=-8 jkkk

by lens formula, kkkkk

1/f=1/v-1/u kkkj

1/v=1/f+1/u

1/v=1/10+1/(-8)

1/v=4-5/40

v=-40

So the image is Negative ,

it is virtual, magnified when kept the object between Pole and f1.