Given that,
Radius of mirror = 20 cm
Size of image = 3 times of size of object
We need to calculate the distance of the screen from the mirror
Using formula of magnification
[tex]m=-\dfrac{h'}{h}=\dfrac{v}{u}[/tex]
[tex]-\dfrac{h'}{h}=\dfrac{v}{u}[/tex]
Where, h' = size of image
h = size of object
v = image distance from mirror
u = object distance from mirror
Put the value into the formula
[tex]-\dfrac{3h}{h}=\dfrac{-v}{u}[/tex]
[tex]\dfrac{3}{1}=\dfrac{v}{u}[/tex]
[tex]v=3u[/tex]
The distance of image will three times of object distance.
Hence, The distance of the screen from the mirror is 3u.
