electromagnetic waves and refraction

• all EM waves are transverse that transfer energy from a soruce to the absorber.
• all EM waves travel at the same speed through air or a vacuum.
• EM waves form a continuous spectrum over a range of frequencies. They are grouped into seven basic types, based on their wavelength and frequency
• there is such range of frequencies because EM waves are generated by a variety of changes in atoms and their nuclei. Changes in the nucleus of an atoms creates gamma rays, this also explains why atoms can absorb a range of frequencies

  
• different EM waves have different purposes
• when a wave crosses a boundary between materials at an angle it changes direction - refracted
• how much the wave is refracted depends on how much the wave speeds up or slows down, which usually depends on the density of the two materials. the higher the density, the slower a wave will travel through it
• if a wave crosses a boundary and slows down, it will bend towards the normal. if it crosses a material and speeds up, it bends away from the normal
• the wavelength changes when refracted, but frequency stays the same
• if the wave is travelling along the normal it will change speed but is not refracted
• the optical density of a material is a measure of how quickly light can travel through it - the higher the optical density, the slower light waves can travel through it