To determine the image distance, we use the formula relating the focal length, image distance and the distance of the object from the lens. It is expressed as:
1/f = 1/d1 + 1/d2
where f is the focal length, d1 is the distance from the lens and d2 is the image distance.
1/1.5 = 1/2.0 + 1/d2
d2 = 6 cm