posted by Joe .
An object is placed 4 cm in front of a concave lens of focal length 3 cm. Using the lens equation, find where the image will form and state whether it is a real or virtual image.
Learn the lens equation and apply it.
1/do + 1/di = 1/f
do is the object distance = 4 cm
di is the image distance
f is the focal length = 3 cm
If di is positive, the image is real.