Waves

All waves will reflect from a boundary between two mediums (two different substances). If a boundary is very reflective (a mirror) most of the wave will reflect and only some will go through the boundary. Waves can be represented by a wave ray or wave front. 

Law of reflection: When a wave reflects from a plane mirror the angle of reflection will equal  angle of incidence. 

When light reflects of a mirror there will be an image. The image in the mirror is always virtual, this means it's not in real space. To work out where the virtual image is, draw two rays reflecting the same part of the object, and continue the reflected rays into the mirror. Where they meet is where the image of the object is.  

Waves undergo a change of direction (they bend) when they are refracted at the boundary between two materials. The light ray will bend towards the normal when entering a denser material, it will bend away from the material when entering a less dense material. 

Refraction happens because there is a change of speed in the wave, in the denser medium the ray travels slower, in the less dense medium it travels faster.

Wave fronts are the best way to show this. The part of the wave front that hits the different medium first causes the wave front to turn because one side is going slower than the other side.

When the wave enters a denser medium its speed reduces. This mean its wave length shortens and its frequency remains constant.  

All waves transfer energy using oscillations (vibrations).There are two types of waves; 

• Mechanical waves = use the forces between particles to transfer energy, for example sound waves, water waves and seismic 'p' waves. 
• Electromagnetic waves = (light waves) these are oscillating electrised magnetic fields. They can travel through a vacuum.(gravitational waves).

Longitudinal Waves = Has the direction of the oscillations parallel to the direction of energy transfer. These include sound and seismic 'p' waves. 

Transverse Waves = Has the oscillations of particls which are perpendicuclar to the direction of energy transfer. These include light (electromagnetic) and water waves. 

Wave Speed Equation = 

speed of wave = frequency x wavelength

For a given medium the wave speed is constant, if the wave speed is constant then the frequency increases/decreases and wavelength will decrease/increase, ie inversely proportional. 

The wave length is the distance between the crests (or troughs) of a wave.

The amplitude of a wave is the distance between the equilitum position of the wave and the crest or trough.

The frequency of a wave is the number of wavelengths passing a point every second. So the unit is called hertz 'Hz'.