Physics waves

Terms: Longitudinal   Transverse   Mechanical Waves   Electromagnetic waves   Period T (time for one wave to complete)   Amplitude (height of wave)   Frequency (number of waves per second)

Longitudinal waves are compressions travelling through partacles

Transverse waves are oscillations pulsating at right angles to the direction of wave travel

A wave traveling across or through a string/air collunm will reflect at the end of the medium. This reflected wave is at 180 degrees phase shift and causes superposition with the incident wave. These can either cause constructive interfearence (anti-nodes) or destructive interfearance (nodes)

Standing waves can only make harmonies when the wavelenth and length of air collumn or string are proportional (ie 1/2 wavelength, 1 wavelength, 3/4 wavelength, 2 wavelength etc)

The angle of phase is the same as the positioning of a partacle on the wave

Interfearence in two dimensions is when diffrection through two gaps or two wavefronts interfere. They cross over causing constructive and destructive interference causing lines of nodes and anti-nodes

V = f x wavelength           wavelength = 2l    so      v = sq root ( T / mew )
  Where  T = tension  and    mew = the mass per unit length  (kg m^-1)

Light waves have magnetic fields, this oscilates at 90 degrees to oscilation of the wave

Un polarised light contains waves that oscilate in all directions at right angles to the direction of travel

A polarising filter, stops all waves in the light except the ones that are oscilating in the direction of a specific plane. This light now has only one plane of polaisation.

Plane polarisation happens naturally on earth (water surfaces for example) once reflected off of a surface the light becomes polarised to one plane. Photographers use this theory in taking photos of water features. They can avoid glare by stoping the plane polarised light from water surfaces, allowing them to see under the water.

Diffraction occurs when waves travell through a gap. The amount of spread (ie bending or curving of a wave) increases as the gap size : wavelength ratio gets smaller

Huygen's construction is the idea that on every wavefront there are points that are sources of wavelets, the point where these wavelets interfere and cross over is where the next wavefront occurs.

Lazor diffractions:
Through a single slit, creates a series of bright spots where constructive interference takes place and black spots where destructive interference takes place
Through double slits, this causes the interference in two dimensions, where, the two waves cross each other causing interference where the intensity of the bright spots decreases as you move away from the centre.

Through a diffraction grating, the grating produces bright spots or maxima at angles (wavelength) where the arriving waves are in phase
                             n x wavelenth = d x sin ( angle )
where angle is to normal     d is the speration of lines on the grating      n is order number ( 0 , 1 , 2 etc )

Electrons can be diffracted, this means they must be waves as well as partiacles. They are both, but cannot be both at the same time and when experimented with, they become what you want them to be.
You can use this principle to measure diametres and sizes of atoms using the equation: b = ( n x wavelength x L ) / S but the value for n being ( n=1= 1.22 , n=2= 2.23) where S is radius of nth dark ring and L is the distance between diffraction partacles

The de Broglie equation:  wavelength = h / p