字幕列表 影片播放 列印英文字幕 In this nugget we will learn about the electromagnetic spectrum. The spectrum of electromagnetic radiation is extremely wide. It ranges from the wavelengths of long-wave radio transmissions (up to 2000 metres), via short-wave AM and FM radio (wavelengths from 100 meter to a few meters), microwave, radar transmission waves and transmission from similar objects. The wavelength of heat or radiation lies at wavelengths of less than one thousandth of a millimeter. Finally, we have radiation with a wavelength between 780 and 380 nanometers (millionth of a millimeter, or 10 to the power minus 9 meters), which is the visible part of the electromagnetic spectrum and therefore referred to as light. Different wavelengths in the visible part of the spectrum result in different colour impressions as wavelength decreases. At lower wavelengths we have the ultraviolet region. The longer wavelengths in this UV range are part of the radiation we receive from the sun and are considered beneficial (UVA). They result in tanning of the skin. Shorter-wave ultraviolet radiation (UVB), on the other hand, is potentially dangerous to the skin and eyes, although we need it in small quantities because UVB produces vitamin D. The shortest ultraviolet radiations (UVC) are used as disinfectants since they kill bacteria. Still shorter wavelengths bring us first to X-rays, which penetrate the body, and then to the highly-dangerous gamma-rays, emitted as a result of nuclear decomposition. Finally we come to the Cosmic rays, which result from collisions between extremely-fast-moving particles travelling from the outposts of the universe. Cosmic rays have wavelengths down to 10 to the power minus 18 meters. In this nugget, we described the spectrum of the electromagnetic radiation. A spectrum is a range of wavelengths which consists of frequencies that can vary from the invisible radio and gamma waves to the visible light spectrum. Thank you.