Electromagnetic Waves

• Wave properties:

  They can travel through a vacuum

  They travel at speed of light through a vacuum -(3.0*10^8)

  Have oscillating electric and magnetic fields
• Electromagnetic waves are classified by wavelength:

  
  

  Radio Waves: Wavelength 10^3

  Microwaves: Wavelength 10^-2

  Infrared: Wavelength 10^-5

  Visible light Wavelength: 700 nm-400 nm
• Electromagnetic waves are classified by wavelength:

  
  

  Ultraviolet: Wavelength 10^-7

  X-rays: Wavelength 10^-9

  Gamma Rays: Wavelength <10^-12
• The Refractive index(n) can be used to determine the angle of refraction to the medium

  n(Refractive index) = C(Speed of light)/V(Speed of light in the medium)
• Speed of light through a material will always be less than through a vacuum
• Snell's Law

  When light is incident at an angle to the boundary between 2 transparent media- the angle of refraction depends on:

  Angle of incidence of first material

  Speed of light in each material

  n1 sine1=n2 sin2

  
• Two conditions are required for TIR:

  light must be travelling from a material with a higher refractive index to a material with a lower refractive index

  Angle of incidence of the ray to the normal must be above the critical angle

  If the incidence angle = Critical angle, then light refracts along the boundary between the 2 media
• Total internal reflection occurs at a boundary between 2 transparent media- with no refraction, all of the light is reflected back to the original medium
• Total internal refraction formula:

  
  

  SinC = 1 / n (refractive index of material travelling into)
• Polarisation of waves is a property of transverse waves:

  Longitudinal waves cannot be polarised as all their oscillations are already limited to a single plane
• A wave is plane polarised if the particles oscillate in a single plane perpendicular to the direction of energy transfer
• Critical angle is the angle of incidence of which the angle of refraction will be 90 degrees