Question

What is the focal length of concave mirror that magnifies , by a factor of +3.2 , an object that is placed 30cm from the mirror?

Answer 1

23 cm

Step-by-step 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;

`(1)/(u) +(1)/(v) =(1)/(f)`

where f is the focal length and u is object distance

use values in the equation as;

`(1)/(30) +(1)/(96 ) =(1)/(f)`

`(1)/(f) =(7)/(160)`

f=160/7

f=22.86

f= 23 cm ----------nearest a cm