File Name: electromagnetic spectrum and typical applications .zip
Electromagnetic waves have a vast range of practical everyday applications that includes such diverse uses as communication by cell phone and radio broadcasting, WiFi, cooking, vision, medical imaging, and treating cancer.
In this module, we discuss how electromagnetic waves are classified into categories such as radio, infrared, ultraviolet, and so on. We also summarize some of the main applications for each range. The different categories of electromagnetic waves differ in their wavelength range, or equivalently, in their corresponding frequency ranges.
Their properties change smoothly from one frequency range to the next, with different applications in each range. The term radio waves refers to electromagnetic radiation with wavelengths greater than about 0. Radio waves are commonly used for audio communications i. Radio waves typically result from an alternating current in the wires of a broadcast antenna. They cover a very broad wavelength range and are divided into many subranges, including microwaves, electromagnetic waves used for AM and FM radio, cellular telephones, and TV signals.
The accelerating charge in the ac currents of electrical power lines produce electromagnetic waves in this range. ELF waves are able to penetrate sea water, which strongly absorbs electromagnetic waves of higher frequency, and therefore are useful for submarine communications.
In order to use an electromagnetic wave to transmit information, the amplitude, frequency, or phase of the wave is modulated , or varied in a controlled way that encodes the intended information into the wave. In AM radio transmission, the amplitude of the wave is modulated to mimic the vibrations of the sound being conveyed.
The electromagnetic wave produces a current in a receiving antenna, and the radio or television processes the signal to produce the sound and any image. The higher the frequency of the radio wave used to carry the data, the greater the detailed variation of the wave that can be carried by modulating it over each time unit, and the more data that can be transmitted per unit of time.
Cell phone conversations, and television voice and video images are commonly transmitted as digital data, by converting the signal into a sequence of binary ones and zeros. This allows clearer data transmission when the signal is weak, and allows using computer algorithms to compress the digital data to transmit more data in each frequency range. Computer data as well is transmitted as a sequence of binary ones and zeros, each one or zero constituting one bit of data.
Microwaves are the highest-frequency electromagnetic waves that can be produced by currents in macroscopic circuits and devices. Along with other ranges of electromagnetic waves, they are part of the radiation that any object above absolute zero emits and absorbs because of thermal agitation , that is, from the thermal motion of its atoms and molecules.
Most satellite-transmitted information is carried on microwaves. Radar is a common application of microwaves. By detecting and timing microwave echoes, radar systems can determine the distance to objects as diverse as clouds, aircraft, or even the surface of Venus.
Microwaves of 2. This creates two separated centers of equal and opposite charges, giving the molecule a dipole moment. The oscillating electric field of the microwaves inside the oven exerts a torque that tends to align each molecule first in one direction and then in the other, with the motion of each molecule coupled to others around it.
This pumps energy into the continual thermal motion of the water to heat the food. The plate under the food contains no water, and remains relatively unheated. The microwaves in a microwave oven reflect off the walls of the oven, so that the superposition of waves produces standing waves, similar to the standing waves of a vibrating guitar or violin string Normal Modes of a Standing Sound Wave. A rotating fan acts as a stirrer by reflecting the microwaves in different directions, and food turntables, help spread out the hot spots.
Consider the waves along one direction in the oven, being reflected at the opposite wall from where they are generated. The antinodes, where maximum intensity occurs, are half the wavelength apart, with separation. The distance between the hot spots in a microwave oven are determined by the wavelength of the microwaves. A cell phone has a radio receiver and a weak radio transmitter, both of which can quickly tune to hundreds of specifically assigned microwave frequencies.
The low intensity of the transmitted signal gives it an intentionally limited range. A ground-based system links the phone to only to the broadcast tower assigned to the specific small area, or cell, and smoothly transitions its connection to the next cell when the signal reception there is the stronger one. This enables a cell phone to be used while changing location. Microwaves also provide the WiFi that enables owners of cell phones, laptop computers, and similar devices to connect wirelessly to the Internet at home and at coffee shops and airports.
A wireless WiFi router is a device that exchanges data over the Internet through the cable or another connection, and uses microwaves to exchange the data wirelessly with devices such as cell phones and computers.
The term WiFi itself refers to the standards followed in modulating and analyzing the microwaves so that wireless routers and devices from different manufacturers work compatibly with one another.
The computer data in each direction consist of sequences of binary zeros and ones, each corresponding to a binary bit. The microwaves are in the range of 2. Other wireless technologies also use microwaves to provide everyday communications between devices. Bluetooth developed alongside WiFi as a standard for radio communication in the 2. Microwaves find use also in radio tagging, using RFID radio frequency identification technology.
The device responds to a microwave signal by emitting a signal of its own with encoded information, allowing stores to quickly ring up items at their cash registers, drivers to charge tolls to their account without stopping, and lost pets to be reunited with their owners.
NFC near field communication works similarly, except it is much shorter range. Its mechanism of interaction is the induced magnetic field at microwave frequencies between two coils. Cell phones that have NFC capability and the right software can supply information for purchases using the cell phone instead of a physical credit card.
The very short range of the data transfer is a desired security feature in this case. Infrared radiation is generally produced by thermal motion, and the vibration and rotation of atoms and molecules. Electronic transitions in atoms and molecules can also produce infrared radiation. About half of the solar energy arriving at Earth is in the infrared region, with most of the rest in the visible part of the spectrum.
The range of infrared frequencies extends up to the lower limit of visible light, just below red. Reconnaissance satellites can detect buildings, vehicles, and even individual humans by their infrared emissions, whose power radiation is proportional to the fourth power of the absolute temperature. More mundanely, we use infrared lamps, including those called quartz heaters , to preferentially warm us because we absorb infrared better than our surroundings.
If you try to use a TV remote without the infrared emitter being in direct line of sight with the infrared detector, you may find the television not responding.
Some remotes use Bluetooth instead and reduce this annoyance. Visible light is the narrow segment of the electromagnetic spectrum between about nm and about nm to which the normal human eye responds. Visible light is produced by vibrations and rotations of atoms and molecules, as well as by electronic transitions within atoms and molecules.
The receivers or detectors of light largely utilize electronic transitions. Blackbody radiation from the Sun peaks in the visible part of the spectrum but is more intense in the red than in the violet, making the sun yellowish in appearance. Living things - plants and animals - have evolved to utilize and respond to parts of the electromagnetic spectrum in which they are embedded. We enjoy the beauty of nature through visible light. Plants are more selective. Photosynthesis uses parts of the visible spectrum to make sugars.
The highest-frequency ultraviolet overlaps with the lowest-frequency X-rays. The wavelengths of ultraviolet extend from nm down to about 10 nm at its highest frequencies.
Ultraviolet is produced by atomic and molecular motions and electronic transitions. Sunburn is caused by large exposures to UV-B and UV-C, and repeated exposure can increase the likelihood of skin cancer. The tanning response is a defense mechanism in which the body produces pigments in inert skin layers to reduce exposure of the living cells below.
As examined in a later chapter, the shorter the wavelength of light, the greater the energy change of an atom or molecule that absorbs the light in an electronic transition. This makes short-wavelength ultraviolet light damaging to living cells. It also explains why ultraviolet radiation is better able than visible light to cause some materials to glow, or fluoresce.
Besides the adverse effects of ultraviolet radiation, there are also benefits of exposure in nature and uses in technology. Vitamin D production in the skin results from exposure to UV-B radiation, generally from sunlight. Several studies suggest vitamin D deficiency is associated with the development of a range of cancers prostate, breast, colon , as well as osteoporosis.
Low-intensity ultraviolet has applications such as providing the energy to cause certain dyes to fluoresce and emit visible light, for example, in printed money to display hidden watermarks as counterfeit protection.
They have shorter wavelengths, and higher frequencies, than ultraviolet, so that the energy they transfer at an atomic level is greater.
As a result, X-rays have adverse effects on living cells similar to those of ultraviolet radiation, but they are more penetrating. Cancer and genetic defects can be induced by X-rays. Because of their effect on rapidly dividing cells, X-rays can also be used to treat and even cure cancer. The widest use of X-rays is for imaging objects that are opaque to visible light, such as the human body or aircraft parts.
In humans, the risk of cell damage is weighed carefully against the benefit of the diagnostic information obtained.
Soon after nuclear radioactivity was first detected in , it was found that at least three distinct types of radiation were being emitted, and these were designated as alpha, beta, and gamma rays.
Gamma rays have characteristics identical to X-rays of the same frequency—they differ only in source. They have many of the same uses as X-rays, including cancer therapy. Gamma radiation from radioactive materials is used in nuclear medicine.
Use this simulation to explore how light interacts with molecules in our atmosphere. How do the electromagnetic waves for the different kinds of electromagnetic radiation differ? They fall into different ranges of wavelength, and therefore also different corresponding ranges of frequency. Samuel J. Learning Objectives By the end of this section, you will be able to: Explain how electromagnetic waves are divided into different ranges, depending on wavelength and corresponding frequency Describe how electromagnetic waves in different categories are produced Describe some of the many practical everyday applications of electromagnetic waves.
Radio Waves The term radio waves refers to electromagnetic radiation with wavelengths greater than about 0. Microwaves Microwaves are the highest-frequency electromagnetic waves that can be produced by currents in macroscopic circuits and devices. Interactions between the molecules distributes the energy being pumped into them. Strategy Consider the waves along one direction in the oven, being reflected at the opposite wall from where they are generated.
Visible Light Visible light is the narrow segment of the electromagnetic spectrum between about nm and about nm to which the normal human eye responds. A small part of the electromagnetic spectrum that includes its visible components.
In this module we examine how electromagnetic waves are classified into categories such as radio, infrared, ultraviolet, and so on, so that we can understand some of their similarities as well as some of their differences. We will also find that there are many connections with previously discussed topics, such as wavelength and resonance. A brief overview of the production and utilization of electromagnetic waves is found in Table There are many types of waves, such as water waves and even earthquakes. Among the many shared attributes of waves are propagation speed, frequency, and wavelength.
PDF | On Jan 1, , Joanne Zwinkels published Light, Electromagnetic Spectrum | Find, read Electromagnetic spectrum is deﬁned as the shows the SPD of a typical tungsten lamp, a Applications of Electromagnetic.
Light waves across the electromagnetic spectrum behave in similar ways. When a light wave encounters an object, they are either transmitted, reflected, absorbed, refracted, polarized, diffracted, or scattered depending on the composition of the object and the wavelength of the light. Specialized instruments onboard NASA spacecraft and airplanes collect data on how electromagnetic waves behave when they interact with matter.
In physics , radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. Radiation is often categorized as either ionizing or non-ionizing depending on the energy of the radiated particles. Ionizing radiation carries more than 10 eV , which is enough to ionize atoms and molecules and break chemical bonds.
The behaviour of an electromagnetic wave in a substance depends on its frequency or wavelength. The differing behaviours of different groups in the electromagnetic spectrum make them suitable for a range of uses. Radio waves are used for communication such as television and radio.
Electromagnetic waves have a vast range of practical everyday applications that includes such diverse uses as communication by cell phone and radio broadcasting, WiFi, cooking, vision, medical imaging, and treating cancer. In this module, we discuss how electromagnetic waves are classified into categories such as radio, infrared, ultraviolet, and so on. We also summarize some of the main applications for each range. The different categories of electromagnetic waves differ in their wavelength range, or equivalently, in their corresponding frequency ranges. Their properties change smoothly from one frequency range to the next, with different applications in each range.
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