Answer:
23 cm
Explanation:
The formula for magnification is;
Magnification = image distance / object distance
use values as;
3.2 = v / 30 where v is image distance
v =30*3.2
v=96 cm
The relationship of the focal length with image distance and object distance is expressed as;
[tex]\frac{1}{u} +\frac{1}{v} =\frac{1}{f}[/tex]
where f is the focal length and u is object distance
use values in the equation as;
[tex]\frac{1}{30} +\frac{1}{96 } =\frac{1}{f}[/tex]
[tex]\frac{1}{f} =\frac{7}{160}[/tex]
f=160/7
f=22.86
f= 23 cm ----------nearest a cm
