Microwave & Radio waves - senshido.info
The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic Radiation of visible light wavelengths and lower are called nonionizing radiation as Radio frequency; Microwaves; Terahertz radiation; Infrared radiation These relations are illustrated by the following equations. ship between energy and frequency is given by the equation, E = hν, where h of increasing energy, these include radio waves, television waves, microwaves. This broad range of wavelengths is known as the electromagnetic Microwaves have frequencies ranging from about 1 billion cycles per.
The video and text below describes some of the characteristics and uses of Radio waves and Microwaves. Radio Waves Radio waves are the lowest-energy, lowest-frequency and longest-wavelength electromagnetic waves. They are produced when an alternating current flows in an aerial and they spread out and travel through the atmosphere. They are not strongly absorbed by the atmosphere.
Another aerial is used as a detector and the waves produce an alternating current in it, with a frequency that matches that of the radio waves. Anyone with a receiver can tune it to this frequency to pick up the radio waves so they are suitable for broadcasting for example, radio and TV programmes to large numbers of people. An advantage is that this method of communicating does not require wires to transmit information. A disadvantage is that radio stations using similar transmission frequencies sometimes interfere.
A common mistake is to think that we can hear radio waves. We cannot hear any electromagnetic radiation.
Radio waves & microwaves
The radiation is used to carry a signal that is converted into a sound wave by the receiver. Medium wavelength radio waves are reflected from the ionosphere, a layer of charged particles in the upper atmosphere, so they can be used for long distance communication. Digital radio has better-quality reception as it uses digital signals and so does not have problems of noise and interference.
Microwaves Microwaves are sometimes considered to be very short radio waves highfrequency and high-energy radio waves. Some important properties of microwaves are: They are reflected by metal surfaces. They heat materials if they can make atoms or molecules in the material vibrate.
The amount of heating depends on the intensity of the microwave radiation, and the time that the material is exposed to the radiation. They pass through glass and plastics. They pass through the atmosphere. They pass through the ionosphere without being reflected. They are absorbed by water molecules, how well depends on the frequency energy of the microwaves. Transmission is affected by wave effects such as reflection, refraction, diffraction and interference. Microwaves and water molecules A microwave frequency energy can be selected which is strongly absorbed by water molecules, causing them to vibrate, and increasing their kinetic energy.
This effect can be used to heat materials containing water, for example food. If the most strongly absorbed frequency energy is used in a microwave oven it only cooks the outside of the food because it is all absorbed before it penetrates the food.
They are also used for remote controland for industrial heating. The use of the radio spectrum is strictly regulated by governments, coordinated by a body called the International Telecommunications Union ITU which allocates frequencies to different users for different uses. Microwaves Plot of Earth's atmospheric transmittance or opacity to various wavelengths of electromagnetic radiation. Microwaves are radio waves of short wavelengthfrom about 10 centimeters to one millimeter, in the SHF and EHF frequency bands.
Although they are emitted and absorbed by short antennas, they are also absorbed by polar moleculescoupling to vibrational and rotational modes, resulting in bulk heating. Unlike higher frequency waves such as infrared and light which are absorbed mainly at surfaces, microwaves can penetrate into materials and deposit their energy below the surface.
This effect is used to heat food in microwave ovensand for industrial heating and medical diathermy. Microwaves are the main wavelengths used in radarand are used for satellite communicationand wireless networking technologies such as Wi-Fialthough this is at intensity levels unable to cause thermal heating.
The copper cables transmission lines which are used to carry lower frequency radio waves to antennas have excessive power losses at microwave frequencies, and metal pipes called waveguides are used to carry them. Although at the low end of the band the atmosphere is mainly transparent, at the upper end of the band absorption of microwaves by atmospheric gasses limits practical propagation distances to a few kilometers. Terahertz radiation Main article: Terahertz radiation Terahertz radiation is a region of the spectrum between far infrared and microwaves.
Until recently, the range was rarely studied and few sources existed for microwave energy at the high end of the band sub-millimeter waves or so-called terahertz wavesbut applications such as imaging and communications are now appearing.
Electromagnetic spectrum - Wikipedia
Scientists are also looking to apply terahertz technology in the armed forces, where high-frequency waves might be directed at enemy troops to incapacitate their electronic equipment.
Infrared radiation Main article: It can be divided into three parts: The lower part of this range may also be called microwaves or terahertz waves. This radiation is typically absorbed by so-called rotational modes in gas-phase molecules, by molecular motions in liquids, and by phonons in solids. The water in Earth's atmosphere absorbs so strongly in this range that it renders the atmosphere in effect opaque.
However, there are certain wavelength ranges "windows" within the opaque range that allow partial transmission, and can be used for astronomy. Mid-infrared, from 30 to THz 10—2. Hot objects black-body radiators can radiate strongly in this range, and human skin at normal body temperature radiates strongly at the lower end of this region. This radiation is absorbed by molecular vibrations, where the different atoms in a molecule vibrate around their equilibrium positions.
This range is sometimes called the fingerprint region, since the mid-infrared absorption spectrum of a compound is very specific for that compound. Physical processes that are relevant for this range are similar to those for visible light.
The highest frequencies in this region can be detected directly by some types of photographic film, and by many types of solid state image sensors for infrared photography and videography.
Visible radiation light Main article: Visible spectrum Above infrared in frequency comes visible light. The Sun emits its peak power in the visible region, although integrating the entire emission power spectrum through all wavelengths shows that the Sun emits slightly more infrared than visible light. Visible light and near-infrared light is typically absorbed and emitted by electrons in molecules and atoms that move from one energy level to another.How To Calculate The Energy of a Photon Given Frequency & Wavelength in nm Chemistry
This action allows the chemical mechanisms that underlie human vision and plant photosynthesis. The light that excites the human visual system is a very small portion of the electromagnetic spectrum. A rainbow shows the optical visible part of the electromagnetic spectrum; infrared if it could be seen would be located just beyond the red side of the rainbow with ultraviolet appearing just beyond the violet end.
White light is a combination of lights of different wavelengths in the visible spectrum. If radiation having a frequency in the visible region of the EM spectrum reflects off an object, say, a bowl of fruit, and then strikes the eyes, this results in visual perception of the scene.
The brain's visual system processes the multitude of reflected frequencies into different shades and hues, and through this insufficiently-understood psychophysical phenomenon, most people perceive a bowl of fruit.
At most wavelengths, however, the information carried by electromagnetic radiation is not directly detected by human senses. Natural sources produce EM radiation across the spectrum, and technology can also manipulate a broad range of wavelengths.