Electromagnetic wave

Electromagnetic waves are composed of oscillating magnetic and electric fields. So all forms of light within the electromagnetic spectrum can be thought of as vibrations produced as a result of the interaction between an electric field and a magnetic field.

  • Electromagnetic waves carry electromagnetic radiant energy.
  • The energy carried by electromagnetic waves is often simply called radiant energy or light.
  • We can feel electromagnetic waves release their energy when sunlight warms our skin.
  • The amount of energy they carry is related to their frequency and their amplitude. The higher the frequency, the more energy, and the higher the amplitude, the more energy.
  • The three principal properties of an electromagnetic wave are:
    • Velocity (v): The measure of how fast and in what direction a wave propagates in a given medium.
    • Wavelength (λ): The distance over which the shape of a wave repeats. Wavelength is measured in meters or its sub-units.
    • Frequency (f): Frequency is measured in cycles per second. The unit of frequency is Hertz or its sub-units.
  • Each of these three quantities for describing EM radiation are related to one another in a precise mathematical way.
  • The position of an electromagnetic wave in the electromagnetic spectrum can be characterized by either its frequency of oscillation or wavelength.
  • The electromagnetic spectrum includes, in order of increasing frequency and decreasing wavelength: radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.
About the properties of photons
  • A photon is a single indivisible bundle (particle or wave) of energy within an electromagnetic field.
  • A photon is an elementary particle and represents a quantum (plural =quanta) of light – the smallest quantity into which light can be divided.
  • Whilst the field of optics often explains light in terms of waves, this description doesn’t always fit the evidence.
  • Light sometimes exhibits wave-like behaviour, at others, it behaves like both waves and particles or just as particles.

Other properties of photons include:

  • They have zero mass and rest energy. They only exist as moving particles.
  • They are elementary particles despite lacking rest mass.
  • They have no electric charge.
  • They are stable.
  • They carry energy and momentum which are dependent on the frequency.
  • They can have interactions with other particles such as electrons.
  • They can be destroyed or created by many natural processes, for instance when radiation is absorbed or emitted.
  • When in empty space, they travel at the speed of light.

An electromagnetic wave carries electromagnetic radiation.

  • An electromagnetic wave is formed as electromagnetic radiation propagates from a light source, travels through space and encounters different materials.
  • Electromagnetic waves can be imagined as synchronised oscillations of electric and magnetic fields that propagate at the speed of light in a vacuum.
  • Electromagnetic waves are similar to other types of waves in so far as they can be measured in terms of wavelength, frequency and amplitude.
  • We can feel electromagnetic waves release their energy when sunlight warms our skin.
  • Remember that electromagnetic radiation can be described either as an oscillating wave or as a stream of particles, called photons, which also travel in a wave-like pattern.
  • The notion of waves is often used to describe phenomena such as refraction or reflection whilst the particle analogy is used when dealing with phenomena such as diffraction and interference.