The magnification of a lens may be defined as the ratio of the size (height) of the image to the size (height) of the object. The magnification of a lens is represented by the letter ‘m’. Thus,
m = 
or
m = 
Where, h2 = size of image
h1 = size of object
The magnification (m) of lens can also be calculated in terms of image distance (v) and object distance (u), if we do not know the size (height) of object and image. Thus,
m = 
m = 
Where, v = image distance
u = object distance
Please note that the magnification formula is applicable both in convex lenses and concave lenses. And the magnification m is positive when the image formed is virtual and erect. On the other hand, the magnification m is negative when the image formed is real and inverted.
Test Your Understanding and Answer These Questions:
- What do you meant by magnification of a lens?