Energy is propagated through space in the form of electromagnetic (EM) waves, which are composed of oscillating electric and magnetic fields. EM waves do not require a substance (like air or water) to travel through, meaning that — unlike sound — they can travel through empty space. In a vacuum, all EM waves travel at the same speed: the speed of light (which is itself an EM wave). Like all waves, an EM wave is characterised by its wavelength, and the range of wavelengths we observe, from very long to very short, is what we refer to as the EM spectrum. We divide up the EM spectrum roughly according to how the waves behave when they interact with matter and each division has a name. So we have: radio waves, which have the longest wavelengths; microwaves; infrared; visible light; ultraviolet; x-rays; and finally gamma rays, which have the shortest wavelengths. Celestial objects such as stars, planets and galaxies all emit EM waves at various wavelengths and so different telescopes are designed to be sensitive to different parts of the EM spectrum. EM radiation in and around the visible part of the spectrum is often referred to broadly as ‘light’, with shorter wavelengths referred to as ‘bluer’ and longer wavelengths referred to as ‘redder’. The lowest frequency portion of the electromagnetic spectrum is designated as “radio,” generally considered to have wavelengths within 1 millimeter to 100 kilometers or frequencies within 300 GHz to 3 kHz. FM radio waves are also used for commercial radio transmission in the frequency range of 88 to 108 MHz. FM stands for frequency modulation, which produces a wave of constant amplitude but varying frequency.

thermography: Any of several techniques for the remote measurement of the temperature variations of a body, especially by creating images produced by infrared radiation. Electromagnetic spectrum. Provided by: Wikipedia. Located at: en.Wikipedia.org/wiki/Electromagnetic_spectrum. License: CC BY-SA: Attribution-ShareAlike Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency and therefore high energy. Gamma rays typically have frequencies above 10 exahertz (or >10 19 Hz), and therefore have energies above 100 keV and wavelengths less than 10 picometers (less than the diameter of an atom). However, this is not a hard and fast definition, but rather only a rule-of-thumb description for natural processes. Gamma rays from radioactive decay are defined as gamma rays no matter what their energy, so that there is no lower limit to gamma energy derived from radioactive decay. Gamma decay commonly produces energies of a few hundred keV, and almost always less than 10 MeV. The prefix “micro-” in “microwave” is not meant to suggest a wavelength in the micrometer range. It indicates that microwaves are “small” compared to waves used in typical radio broadcasting in that they have shorter wavelengths. non-ionizing radiation: Radiation that does not cause atmospheric ionization; electrically neutral radiation.

Using this poster set to supplement home learning.

Heat is energy in transient form that flows due to temperature difference. Unlike heat transmitted by thermal conduction or thermal convection, radiation can propagate through a vacuum. Boundless. Provided by: Boundless Learning. Located at: www.boundless.com//physics/definition/am-radio-waves. License: CC BY-SA: Attribution-ShareAlike

terahertz radiation. Provided by: Wiktionary. Located at: en.wiktionary.org/wiki/terahertz_radiation. License: CC BY-SA: Attribution-ShareAlikeVisible spectrum. Provided by: Wikipedia. Located at: en.Wikipedia.org/wiki/Visible_spectrum. License: CC BY-SA: Attribution-ShareAlike X-rays have shorter wavelengths (higher energy ) than UV waves and, generally, longer wavelengths (lower energy) than gamma rays. Sometimes X-rays are called Röntgen radiation, after Wilhelm Röntgen, who is usually credited as their discoverer.