Refraction of waves
Different materials have different densities. Light waves may change direction at the boundary between two transparent materials. Process by which a wave changes speed and sometimes direction upon entering a denser or less dense medium, eg a light ray changes direction when refracted by a lens. is the change in direction of a wave at such a boundary.
It is important to be able to draw Diagram that represents the direction and angle of travel of light. to show the refraction of a wave at a boundary.
Refraction can cause optical illusions as the light waves appear to come from a different position to their actual source.
Explaining refraction - Higher
The A measure of compactness and the ratio of mass to volume. It is usually measured in kilograms per metre cubed (kg/m3) or grams per centimetre cubed (g/cm3). of a material affects the speed that a wave will be A wave is passed across or through a material (medium), eg light waves are transmitted through air, glass and water. through it. In general, the denser the transparent material, the more slowly light travels through it.
Glass is denser than air, so a light ray passing from air into glass slows down. If the ray meets the boundary at an angle to the An imaginary but useful line at right angles to the boundary between air/glass. All angles are measured to this line., it bends towards the normal.
The reverse is also true. A light ray speeds up as it passes from glass into air, and bends away from the normal by the same angle.
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Wave speed, frequency and wavelength in refraction
For a given The number of waves produced each second. The unit of frequency is hertz (Hz). of light, the The length of a single wave, measured from one wave peak to the next. is A relationship between two variables, eg in a gas. As temperature increases, the pressure would also increase proportionally. (If the temperature doubled, the pressure would double). to the wave speed:
wave speed = frequency Ă wavelength
So if a wave slows down, its wavelength will decrease. The effect of this can be shown using wave front diagrams like the one below. The diagram shows that as a wave travels into a denser medium, such as water, it slows down and the wavelength decreases. Although the wave slows down, its frequency remains the same, due to the fact that its wavelength is shorter.
In this diagram, the right hand side of the incoming wave slows down before the left hand side does. This causes the wave to change direction.