Electromagnetic spectrum

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The electromagnetic spectrum (EM spectrum) comprises the different types of radiation and their corresponding frequencies, wavelengths and energy values. The spectrum ranges from radio waves which have the longest wavelength, lowest frequency and highest energy level through to microwaves, infrared, visible light, ultraviolet, x-rays, gamma rays which have shorter wavelengths, higher frequencies and higher energy levels respectively.

Radio waves are used for the transmittance of information in everyday items such as mobile phones, televisions and radio broadcasts. Microwaves are used to heat substances either on a small scale like in a microwave oven or on an industrial scale. Infrared is utilised mainly in thermal imaging cameras. Visible light is the only region on the EM spectrum which can be seen by the human eye[1] and is also the section that can be utilised by plants during photosynthesis as it has a wavelength range of 400-700 nm. Ultraviolet is very useful in forensics and is also responsible for sunburn, though many of the most harmful wavelengths are repelled by the ozone layer. X-rays have a largely medical use as different materials in the human body have different attenuation coefficients of x- rays and therefore a high contrast between bone and muscle for example can be seen. Gamma rays are highly ionising but are mainly used in diagnostic medicine, the primary example currently being Positron Emission Tomography (PET) scans. 

  1. D Sadava, DM Hillis, HC Heller, M Berenbaum. Life: The Science of Biology. 10th Edition. 2014. Sinauer


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