They do not cause damage if absorbed by the human body, and they can be reflected to change their direction. These properties make them ideal for communications.
Radio waves can be produced by oscillations in electrical circuits. When radio waves are absorbed by a conductor , they create an alternating current. This electrical current has the same frequency as the radio waves. The conductor could be, for example, an aerial on a radio. Information is coded into the wave before transmission, which can then be decoded when the wave is received. Television and radio systems use this principle to broadcast information.
Infrared: Night vision goggles pick up the infrared light emitted by our skin and objects with heat. In space, infrared light helps us map the dust between stars. Visible: Our eyes detect visible light. Fireflies, light bulbs, and stars all emit visible light. Ultraviolet: Ultraviolet radiation is emitted by the Sun and are the reason skin tans and burns.
X-ray: A dentist uses X-rays to image your teeth, and airport security uses them to see through your bag. Hot gases in the Universe also emit X-rays. Gamma ray: Doctors use gamma-ray imaging to see inside your body. The biggest gamma-ray generator of all is the Universe. Are radio waves completely different physical objects than gamma-rays?
They are produced in different processes and are detected in different ways, but they are not fundamentally different. Radio waves, gamma-rays, visible light, and all the other parts of the electromagnetic spectrum are electromagnetic radiation. Electromagnetic radiation can be described in terms of a stream of mass-less particles, called photons , each traveling in a wave-like pattern at the speed of light.
Each photon contains a certain amount of energy. The different types of radiation are defined by the the amount of energy found in the photons. Frequency is normally measured in hertz Hz , equivalent to one cycle per second, and various multiples of hertz. Therefore, the two are inversely related to each other. The shorter the wavelength, the higher the frequency. The longer the wavelength, the lower the frequency. Understanding the characteristics of electromagnetic radiation in terms of their wavelength and frequency is crucial to understanding the information to be extracted from remote sensing data.
Next we will be examining the way in which we categorize electromagnetic radiation for just that purpose. Hospitals use imaging technology, including CAT scans, magnetic resonance imaging 3-D imaging of soft tissue , and x-rays for examining our bodies. These are all examples of non-intrusive remote sensing methods. High-pitched sounds have short wavelengths and high frequencies.
Low sounds are the opposite. Scientists say that the Earth itself vibrates at a very low frequency, making a sound far below the human hearing range. Sunlight is also a form of EM energy, but visible light is only a small portion of the EM spectrum, which contains a broad range of electromagnetic wavelengths. Electricity and magnetism were once thought to be separate forces. However, in , Scottish physicist James Clerk Maxwell developed a unified theory of electromagnetism.
The study of electromagnetism deals with how electrically charged particles interact with each other and with magnetic fields. Maxwell also developed a set of formulas, called Maxwell's equations, to describe these phenomena. EM radiation is created when an atomic particle, such as an electron, is accelerated by an electric field, causing it to move.
The movement produces oscillating electric and magnetic fields, which travel at right angles to each other in a bundle of light energy called a photon. Photons travel in harmonic waves at the fastest speed possible in the universe: , miles per second ,, meters per second in a vacuum, also known as the speed of light.
The waves have certain characteristics, given as frequency, wavelength or energy. A wavelength is the distance between two consecutive peaks of a wave.
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