Question

Write 3 characteristics of the image formed by a convex lens of focal length 20 cm for the object at a distance of 30 cm.
Explain the concept you have used.

Answer 1

given lens is convex lens
so,
focal length ( f ) = 20 cm
object distance ( u ) = -30 cm

use lens formula ,
1/ v - 1/u = 1/ f
1/ v - 1/(-30) = 1/(20)
1/v = -1/30 +1/20
= 1/60
v = 60 cm

1) image form right side of pole of convex lens .

2) image 's nature is real and inverted

3) magnification = v/u
= (60)/(-20) =-3
magnification =3 it means height of image is 3 times height of object . and negative sign show that image will be inverted .

Answer 2

given:-
focal length (f) = 20 cm
object distance (u) = 30 cm

let the image distance be v cm

FORMULA:-

1/v + 1/u = 1/f

1/v + 1/30 = 1/20
1/v = 1/20 - 1/30
1/v = (3 - 2)/60
1/v = 1/60
v= 60

focal length = 20 cm
center of curvature = 2(20) cm = 40 cm

the image distance(60) > center of curvature(40)

therefore the image is formed beyond center of curvature

characteristics:-
1)Image is enlarged.
2)the image is real
3)the image is inverted.