Given:
The focal length of the lens, f=3.12 m
The height of the film, h=0.30 m
The height of the image, h_i=0.83 m
To find:
The magnification of the lens.
Step-by-step explanation:
The magnification of a lens is given by,

On substituting the known values,

Final answer:
The magnification of the lens is 2.77