The electromagnetic spectrum, or EM spectrum, is the name given to the collection of all electromagnetic radiation in the universe. This is a type of energy that pervades the cosmos in the form of electric and magnetic waves, allowing for the transfer of energy and information. Discovered more than a century ago, the electromagnetic spectrum is the basis on which our universe operates. It is one of the most important principles that governs everything around us.
It is also an invaluable tool, used by astronomers to probe the deepest reaches of the cosmos far beyond what our eyes alone can witness.
The information carried on the electromagnetic spectrum provides almost all of our knowledge of how everything as we know it works. The EM spectrum is a range of frequencies that corresponds to all different forms of electromagnetic radiation in the universe.
It begins at the highest frequencies, where the waves are most stretched out low frequency to very tightly packed waves high frequency. These frequencies correspond to different levels of radiation, which is the transmission of energy through the universe in the form of waves and particles. Lower frequency radiation has much longer wavelengths, meaning the distance between the waves of radiation is long, up to many kilometers. When an electrical charge changes its energy condition it leads to moving waves.
These are waves of different frequency and wavelength dependent on the origin. Waves with a long wavelength spread well beyond their surroundings. Radio waves are used to transmit wireless signals to TVs, radios and mobile phones through the air. Microwaves are less widespread and are used where the transmitter and the receiver are closer to each other.
In this spectrum you will, for example, find radar and microwave ovens. 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.
Radio waves have photons with low energies, microwave photons have a little more energy than radio waves, infrared photons have still more, then visible, ultraviolet, X-rays, and, the most energetic of all, gamma-rays.
Electromagnetic radiation can be expressed in terms of energy, wavelength, or frequency. Frequency is measured in cycles per second, or Hertz. Wavelength is measured in meters. Energy is measured in electron volts. Each of these three quantities for describing EM radiation are related to each other in a precise mathematical way.
But why have three ways of describing things, each with a different set of physical units? Comparison of wavelength, frequency and energy for the electromagnetic spectrum.
The short answer is that scientists don't like to use numbers any bigger or smaller than they have to. It is much easier to say or write "two kilometers" than "two thousand meters.
Astronomers who study radio waves tend to use wavelengths or frequencies. Most of the radio part of the EM spectrum falls in the range from about 1 cm to 1 km, which is 30 gigahertz GHz to kilohertz kHz in frequencies. The radio is a very broad part of the EM spectrum. A wavelength is the distance between two consecutive peaks of a wave. This distance is given in meters m or fractions thereof.
Frequency is the number of waves that form in a given length of time. It is usually measured as the number of wave cycles per second, or hertz Hz. A short wavelength means that the frequency will be higher because one cycle can pass in a shorter amount of time, according to the University of Wisconsin. Similarly, a longer wavelength has a lower frequency because each cycle takes longer to complete. EM radiation spans an enormous range of wavelengths and frequencies.
This range is known as the electromagnetic spectrum. The EM spectrum is generally divided into seven regions, in order of decreasing wavelength and increasing energy and frequency.
The common designations are: radio waves, microwaves, infrared IR , visible light, ultraviolet UV , X-rays and gamma rays.
0コメント