At what distance from a simple microscope must an object be placed so that the image 5 times the size of the object is produced 20cm from the lens?

A. 2cm
B. 3.3cm
C. 4cm
D. 5cm
E. 15cm

Correct Answer:

Option C – 4cm

Explanation

M=v/u = 5 ⇒v=5u=20,

let u be x; v= 5x

if v= 20 then 5x = 20

therefore x =20/5 = 4u = 4cm