Question

an object is kept at 40 cm away from the convex of focal length 20 cm what is the nature of the image

Answer 1

Object distance(u) = -40 cm

Focal length(f) = +20 cm

Image distance(v) = ? ,  Magnification(m) = ?

By using lens formula,

1/f = 1/v - 1/u

⇒ 1/v = 1/f + 1/u

= 1/20 + 1/(-40)   = 1/40

⇒ 1/v = 1/40

v = +40 cm

Now, m = v/u

= 40/ (-40) = -1

Hence,the image formed is real, inverted and same size as the object.