Physics 014 Electromagnetic Waves Maxwells Rainbow o o

Physics 014 Electromagnetic Waves

Maxwell’s Rainbow o o Using Maxwell’s Equation’s we find that light is just made of alternating electric and magnetic fields There is a huge spectrum of electromagnetic waves

Maxwell’s Equations

Maxwell’s Rainbow

Traveling EM Waves o o Electromagnetic waves are a type of radiation We will consider waves with wavelengths approximately 1 m

Traveling EM Waves o How is the wave created?

Traveling EM Waves o o o The LC oscillator has an angular frequency ω This will correspond to the frequency of the EM wave The dipole antenna produces a varying E field

Traveling EM Waves

Traveling EM Waves o We can write the fields as Wave number Amplitude Angular frequency

Traveling EM Waves o All electromagnetic waves, including visible light, have the same speed c in vacuum

Poynting Vector o Energy transport per unit area in a wave is described by the Poynting vector S

Poynting Vector o What is most useful is the intensity I of the wave

Reflection and Refraction o o Although light spreads as it travels from a source, it can often be represented as traveling in a straight line This is called the geometrical optics approximation

Reflection and Refraction

Reflection and Refraction o Law of reflection o Law of refraction

Reflection and Refraction o o The constants n 1 and n 2 are called the index of refraction It is the ratio of c (speed of light in vaccum) to the speed of light in the material

Reflection and Refraction o o In certain cases all the light is reflected. This is called total internal reflection

Reflection and Refraction