Question

A 4 cm tall object is placed perpendicular to the principle axis of a convex lens of focal lenght 20 cm if the distance of the object from the lens is 30 cm find the position nature and size of the image also find its magnification​

Answer 1

Answer:Height of the object(h)=4cm

Focal length(f)=+20cm

Object distance(u)= -30cm

1/v - 1/u = 1/f

1/v = 1/u + 1/f

1/v = 1/-30 + 1/20

1/v = -2+3/60

1/v = 1/60

Or v = +60cm

Hence image is real and inverted in nature and formed at a distance of 30cm on the other side of the optical centre.

Now magnification

Magnification(m) = h'/h = v/u

Or h' = h(v/u)

h'= 4×12/30=24/15

h' = -1.6

So the image is enlarged.

Explanation: