Question

An object is placed at a distance 24 cm in front of a convex lens of focal length 8 cm.

(i) What is the nature of the image so formed?
(ii) Calculate the distance of the image from the lens.
(iii) Calculate the magnification of the image.

Answer 1

(i) As for convex lens, if |u| > | f | then real and inverted image is formed and as |u| > 2| f | then it is diminished.

(ii) `1/v - 1/u = 1 /f`

`1/v = 1/u + 1 /f`

`1/v = (f+u)/(uf)`

`⇒ v =(uf)/(f+u)`

= `((-24)(8))/((8)+(-24))`

= `(-24xx8)/(-16)`

= `(-192)/-16`

= 12 cm

(iii) m = `v/u = 12/-24 = -0.5`

The negative sign signifies an inverted image.