How can you distinguish between a real image and a virtual image?

34 With the help of labelled ray diagram only show the formation of an image in a compound microscope. 35 Two thin lenses of power +3.5 D and –2.5 D are placed in contact. Find the power and focal length of the lens combination. 37 State Snell's law 38 How image can be located which is formed by a plane mirror?