An electromagnetic field or EMF is produced when a charged particle is accelerated or put in motion, typically with the introduction of an electrical current. Electrical fields can occur whether the charged particles are static or in motion, but a magnetic field is only produced when the charged particles are in motion, so to produce an EMF, there must be a current present.
As matter is made up of particles, it is possible to find an EMF anywhere in the environment. In fact, EMFs are constantly present all around us, but it is not visible. However, its effects can be observed, depending on two elements: frequency and wavelength.
Frequency is defined as the number of waves generated in a second while wavelength is the measurement from one wave to the next, which depends solely on the frequency. The more waves generated in a second or higher frequency the smaller the distance between waves or shorter wavelength. The different EMF forms are defined by a specific frequency and wavelength, which also determines if they are ionizing or non-ionizing EMFs.
EM waves produce energy. They are carried along by particles referred to as quanta (singular quantum), and high frequency EM waves generate more energy than low frequency waves. When an EMF generates enough energy, it can break the chemical bonds that hold molecules together, and these are called ionizing EMFs. Radioactive materials typically produce ionizing EMFs when they are accelerated, such as gamma rays and X-rays. This is why X-ray technicians don protective clothing, to prevent injury from operating X-ray machines.
EMFs occur naturally, primarily as a result of thunderstorms, which would account for the charged feeling in the air when lightning strikes. They are also generated from man-made objects such as electrical appliances and communication equipment. Lower frequency EMFs that are not strong enough to break bonds between molecules are non-ionizing EMFs, and these include radios, microwaves, and electrical household equipment.