Question

Define linear magnification. Does it have any units? Write down a formula for the magnification produced by a concave mirror in terms of image distance and object distance.

Answer 1

Linear magnification is defined as the ratio of the height of the image to the height of the object. It is taken to be positive for an image to be virtual and erect and negative when the image is real and inverted.
Magnification produced by a concave mirror is:
Magnification = height of image / height of object.
It is a pure ratio and does not have any units.