Answer:
4.8 m
Explanation:
The screen should be placed at at the distance at which the image formed by the lens appears, and this distance can be found by using the lens equation:
[tex]\frac{1}{f}=\frac{1}{p}+\frac{1}{q}[/tex]
where
f=30 cm is the focal length (I assume it is a convex lens, so the focal length has positive sign)
p=32 cm is the distance of the object from the lens
q is the distance of the image from the lens
Re-arranging the equation and replacing the numbers, we can find the value of q:
[tex]\frac{1}{q}=\frac{1}{f}-\frac{1}{p}=\frac{1}{30}-\frac{1}{32}=0.0021 cm^{-1}[/tex]
[tex]q=\frac{1}{0.0021 cm^{-1}}=480 cm[/tex]
so, the screen should be put at 4.8 m from the lens.
