The source of light is a light bulb from a ray box. If a beam of light of one colour is shone through a prism, the direction of the beam is changed by the prism. This is because the two faces of the prism through which the light passes are not parallel. If white light is used the prism splits up the light into a series of colours. This shows that white light is actually made up of many other colours - a fact first shown by Newton in 1666. The spread of colour is called a spectrum. The dispersion of white light into a spectrum occurs because the different colours are refracted by different amounts by the glass of the prism. Violet light is refracted most by a prism and red light is refracted least. The colours of the spectrum are red, orange, yellow, green, blue, indigo and violet.
The source of light is a light bulb from a ray box. If you shine a beam of light through the air, it will travel in a straight line. Rays of light usually travel in straight lines until they hit something.
If a ray of light hits the surface of a sheet of glass, some light will be reflected by the surface of the glass. However, much of the light will pass through the glass, because glass is transparent. When a ray passes from air into glass the direction in which the light ray is travelling changes. The light ray appears to bend as it as it passes through the surface of the glass.
This 'bending of a ray of light' when it passes from one substance into another substance is called refraction.
Glass is thicker and heavier than air. If the light slows down when it passes from the less dense air into the denser glass, this slowing down of the ray of light also causes the ray of light to change direction. It is the change in the speed of the light that causes refraction.
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