Wave Motion

• Mechanical waves: Need a substance for their transmission , e.g sound waves

  Electrimagnetic waves; Do not need a substance for their transmission, e.g light waves through a vacuum
• Types of progressive waves:

  Transverse waves- Where the wave particles vibrate perpendicular to the direction of energy transfer

  longitudinal waves- where the wave particles vibrate parallel to the direction of energy transfer
• Wave properties:

  Displacement: the distance from equilibrium position in a particular direction

  Wavelength: the minimum distance between 2 points on a wave moving in phase

  Amplitude: maximum displacement from equilibrium position
• Wave properties:

  Period: Time taken for one complete oscillation to pass a fixed point

  Frequency: The number of complete oscillations passing a fixed point per second

  wave speed- the distance travelled by a wave per unit time
• Period of a wave is the reciprocal of the frequency

  Period = 1/frequency
• The Wave Equation:

  Wave Speed = Frequency * Wavelength
• Law of Reflection:

  States that whenever waves are reflected the angle of incidence = angle of reflection

  When they are reflected, their wavelength and frequency do not change
• Refraction of Waves:

  If a wave is going into a medium with a higher refractive index it will refract towards the normal

  If a wave is going into a medium with a lower refractive index the light will refract away from the normal

  As a result of this Wavelength also changes depending on speed

  There will always be a partial reflection

  
• Diffraction is the spreading out of waves when they pass through a gap or a obstacle

  we can view this by varying distance and wavelength of waves
• Diffraction effect is greatest when similar to wavelength
• A plane polarised wave is one where the particle oscillations are only in one plane, this is only unique to transverse waves

  Longitudinal waves cannot be polarised as the direction of energy transfer is already in one plane..
• Refraction occurs when a wave changes its direction and its speed when passing from one medium to another
• Intensity of a progressive wave at a point, is the rate at which energy is transferred(power), per unit area perpendicular to the direction of energy transfer
• The total radiant power(p) at distance(r) from a point source is spread out over the area of the sphere through which it passes

  Intensity = Power/area Intensity = Power/4pi r^2
• Intensity(I) has a inverse square relationship with distance(r)

  
• Phase difference is the difference in the displacements of two particles along a wave

  Phase difference = x/wavelength *360