An object 4 cm in size, is placed at 20 cm in front of a concave mirror of focal length 10 cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image?
1
20 cm from the mirror
2
10 cm from the mirror
3
\(\dfrac{20}{3}\) cm from the mirror
4
\(\dfrac{10}{3}\) cm from the mirror