# The Electromagnetic Spectrum: the family of

At GCSE level, from memory you should be able to list the parts in order of energy (relate how that relates to frequency and wavelength) and know how they are produced, detected and their dangers and uses - a rough idea of their approximate wavelength is also useful at GCSE level (but essential at A level!).

The range of values for wavelength is so vast that you need to know your S.I. prefixes to do calculations using the wave equation relating to the EM Spectrum.

 Electromagnetic radiations are disturbances in an electric field. They travel as waves and move energy from one place to another. They can all travel through a vacuum and do so at the same speed. The waves cover a continuous range of wavelengths called the electromagnetic spectrum. The uses and hazards of the radiations in different parts of the electromagnetic spectrum depend on their wavelength and frequency.

The Electromagnetic Spectrum is a continuous band of electromagnetic radiation.

It is not made up of particles of matter - but rather of photons (a concept not met until A level - but the idea is that light is made up of photons which are little quanta (or packets) of energy)).

Electromagnetic radiation is composed of rays of pure energy.All electromagnetic rays have similarities in that they all travel at the same speed in a vacuum - 3.0 x 108 m/s and are all made up of photons.

Electromagnetic waves differ in their wavelength, frequency, energy and method of production, but their speed in a vaccuum is always the same.

 The parts of the electromagnetic spectrum are arranged in the table below in order of decreasing photon energy, decreasing frequency or increasing wavelength. Each part is named according to its origin and frequency/wavelength range. Light energy is the most familiar part of the spectrum and it is often referred to as the 'family of light'. Some parts of the e.m. spectrum can be directly detected by humans, others cannot.

See the table below:

indicates that the rays are harmful because they are of high enough energy to be ionizing radiation.