Question

Describe the nature of image formed when an object is placed at a distance of 30 cm from a convex lens of focal length 15 cm.

Answer 1

Given:
u = -30 cm 
(Since the object is placed on the left side of lens)
Focal length f = +15 cm
According to lens formula: 

`1/v-1/u=1/f`  

or `1/v=1/f+1/u`  

=`1/15+(-1/30)` 

or v=30 cm 

Thus, the image is formed at a distance of 30 cm from the convex lens. The plus sign for image distance shows that the image is formed on the right side of the convex lens. Only real and inverted image is formed on the right side of a convex lens; therefore, the image is real and inverted.