Answer the following with reference to the concept of linear magnification produced by a thin lens.
(a) Define linear magnification and write its mathematical expression in terms of object and image heights.
(b) Using the Cartesian sign convention, explain how the sign of magnification indicates whether the image is erect or inverted.
(c) A converging lens forms an erect image 1.5 times the size of the object when the object is placed 15cm from the lens. Without performing any numerical calculation, state whether the image is real or virtual and justify your answer on the basis of your explanation in part (b).