Arnold K H Tan's answer to Lim Jing Yu's Secondary 4 Biology question.
Is the upright image must use the symbol(-)?
As in the diagram. Upright images are virtual and on the same side as the object, so v = -0.30 m. If its a normal case with a real image on the other side of the lens, v = positive number. This should have been taught by your Physics teacher. Very fundamental knowledge.