Reflection from a smooth, flat surface is called specular reflection. This is the type of reflection that happens with a flat mirror. The image in a mirror is:
In a virtual image, the rays appear to diverge from behind the mirror, so the image appears to come from behind the mirror.
If a surface is rough, diffuse reflection happens. Instead of forming an image, the reflected light is scattered in all directions. This may cause a distorted image of the object, as occurs with rippling water, or no image at all. Each individual reflection still obeys the law of reflection, but the different parts of the rough surface reflect at different angles.
Refraction is the change in direction of a wave at a boundary.
It is important to be able to draw ray diagrams to show the refraction of light at a boundary.
When light is refracted as it enters a prism, each colour is refracted by a different amount. Because each colour has a different wavelength, the speed of each colour is different. This means that the light leaving a prism is separated into its spectrum colours. This a process called dispersion.