Frequency of Electromagnetic Waves

The frequency of an electromagnetic wave is a measurement of the number of wave oscillations passing a given point in a given period of time.

Violet has the highest frequency of visible light.

Lower frequency = Longer wavelengths.

Shorter wavelengths = Higher frequency.

The frequency of a given electromagnetic wave can be calculated by dividing the speed of light in a vacuum (300,000,000 m/s) by its wavelength measured in metres.

The hertz (symbol: Hz) is a unit used to measure the frequency of electromagnetic waves. It represents the number of wave-cycles per second.

• One hertz is defined as one cycle per second.
• Hertz measure the number of oscillations of the perpendicular electric and magnetic fields in electromagnetic radiation per second.
• Frequency conversions:

• 1 Hertz (Hz) = 1 cycle per second
• 1 Kilohertz (kHz) = 1,000 (thousand) cycles per second
• 1 Megahertz (MHz) = 1,000,000 (million) cycles per second
• 1 Gigahertz (GHz) = 1,000,000,000 (billion) cycles per second
• 1 Terahertz (THz) = 1,000,000,000,000 (trillion )cycles per second

Wavelength is the distance from any point on a wave to the corresponding point on the next wave. This measurement is taken along the middle line of the wave.

• While wavelength can be measured from any point on a wave, it is often simplest to measure from the peak of one wave to the peak of the next, or from the bottom of one trough to the bottom of the next, ensuring the measurement covers a whole wave cycle.
• The wavelength of an electromagnetic wave is usually given in metres.
• The wavelength of visible light is typically measured in nanometres, with 1,000,000,000 nanometres making up a metre.
• Each type of electromagnetic radiation – such as radio waves, visible light, and gamma waves – corresponds to a specific range of wavelengths on the electromagnetic spectrum.

A wave-cycle is the complete up-and-down motion of a wave, from one crest (peak) to the next crest, or from one trough (dip) to the next trough. Visualize a wave cycle as a series of points plotted along the path of a wave from one crest to the subsequent crest.

• All electromagnetic waves have common characteristics like crests, troughs,, wavelength, frequency, amplitude, and propagation direction.
• As a wave vibrates, a wave-cycle can be seen as a sequence of individual vibrations, measured from one peak to the next, one trough to the next, or from the start of one wave cycle to the start of the next.
• A wave-cycle refers to the path from one point on a wave during a single oscillation to the same point on completion of that oscillation.
• Wavelength meanwhile, is a measurement of the same phenomenon but in a straight line along the axis of the wave.

Electromagnetic radiation is a type of energy more commonly simply called light. Detached from its source, it is transported by electromagnetic waves (or their quanta, photons) and propagates through space at the speed of light.

• Electromagnetic radiation (EM radiation or EMR) includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays.
• Man-made technologies that produce electromagnetic radiation include radio and TV transmitters, radar, MRI scanners, microwave ovens, computer screens, mobile phones, all types of lights and lamps, electric blankets, electric bar heaters, lasers and x-ray machines.
• At the quantum scale of electromagnetism, electromagnetic radiation is described in terms of photons rather than waves. Photons are elementary particles responsible for all electromagnetic phenomena.
• The term quantum refers to the smallest quantity into which something can be divided. A quantum of a thing is indivisible into smaller units so they have no sub-structure.  A photon is a quantum of electromagnetic radiation.
• A single photon with a wavelength corresponding with gamma rays might carry 100,000 times the energy of a single photon of visible light.

An oscillation is a periodic motion that repeats itself in a regular cycle.

• Oscillation is a characteristic of waves, including electromagnetic waves.
• Examples of oscillation include the side-to-side swing of a pendulum and the up-and-down motion of a spring with a weight attached.
• Electromagnetic waves oscillate due to the transmission of energy by their electric and magnetic fields.
• An oscillating movement is typically around a point of equilibrium and the motion repeats itself around an equilibrium position.

 

 

The frequency of electromagnetic radiation (light) refers to the number of wave-cycles of an electromagnetic wave that pass a given point in a given amount of time.

• Frequency is measured in Hertz (Hz) and signifies the number of wave-cycles per second. Sub-units of Hertz enable measurements involving a higher count of wave-cycles within a single second.
• The frequency of electromagnetic radiation spans a broad range, from radio waves with low frequencies to gamma rays with high frequencies.
• The wavelength and frequency of light are closely linked. Specifically, as the wavelength becomes shorter, the frequency increases correspondingly.
• It is important not to confuse the frequency of a wave with the speed at which the wave travels or the distance it covers.
• The energy carried by a light wave intensifies as its oscillations increase in number and its wavelength shortens.