**Term** |
**Definition** |

Amplitude (A) |
the distance from the middle of the wave to the top (or the bottom) measured in metres. Maximum displacement from the mean position! |

amplitude, (A) |
maximum disturbance of the particles in a wave. (or distance from middle to top of wave) (m) |

Angle of incidence |
the angle between an incident ray and the normal (a line perpendicular to the reflecting surface at the point of incidence) (°) |

Angle of reflection |
the angle between a reflected ray and the normal (°) |

Angle of refraction |
the angle between the light ray in the more optically dense material and the normal. (°) |

Critical angle |
The critical angle is the angle of incidence above which total internal reflection occurs. (°) |

Diffraction |
occurs when wave meet a barrier, the waves bend around an obstacle. Long waves diffract more thank short waves. |

Energy and waves |
Waves transmit energy. The greater the amplitude the more energy is transferred. |

Frequency, (f) |
the number of waves per second. Frequency is measured in hertz (Hz). |

Frequency, (f) |
number of waves produced or passing a point per second. (Hertz or Hz) |

Law of reflection |
The angle of incidence = the angle of reflection |

Longitudinal wave |
In a longitudinal wave the particles move along the line of the direction of travel of energy. |

Normal |
a line at 90° to the surface at the point of incidence, (from which all angles are measured.) |

Period. (T) |
Time for one wave to pass a point or time for one wave to be produced. (s) |

Principle of reversibility of light |
The principle of reversibility of light states that a ray of light which travels along any particular path from some point A to another point B travels by the same path when going from B to A. |

Reflection |
when a wave “bounces off” a surface we say it is reflected. (Particles can also reflect) |

Refraction |
when light waves travel from one material to another the waves slow down and there is a reduction in wavelength in the optical thicker material. Unless the waves enter along the normal there is also a change of direction. |

Speed, (v) |
rate of covering a distance. Number of metres travelled per second. (ms^{-1}) The speed of the waves is represented by the formula |

Total Internal Reflection |
When a wave hits a boundary at an angle larger than the critial angle the wave is entirely reflected if the material on the other side of the boundary is less optically dense. |

Transverse wave |
In a transverse wave the particles move at 90 degrees to the direction of the flow of energy. |

Wave |
a way of transferring energy. |

Wave speed |
the speed at which the wave travels |

Wavelength |
the distance between the same point on successive waves. |

Wavelength, (λ) |
the distance between two successive points on a wave. (metre or m) |

Wavelength, (λ) |
The wavelength of a wave is the horizontal distance between two adjacent troughs or crests or any two corresponding points on the wave |