Electromagnetic sensors are used for measuring the electron concentrations in the earths upper atmosphere and now planetary atmospheres as well, the wavestate of the sea, the moisture content of the lower atmosphere, the moisture in soils and vegetation, the size distributions of. This is the threedimensional wave equation in vector form. Pdf electromagnetic waves and antennas by sophocles j. Electromagnetic waves unlike the waves we met last semester, such as sound waves or waves on a string, no medium is required it is not atoms moving around, but instead the electric and magnetic. Generation of electromagnetic waves with arbitrary orbital angular momentum modes article pdf available in scientific reports 4. The doctoral thesis summarizes the study of the propagation of electromagnetic waves in periodic structures, namely in metamaterials, whereas three forms of a. The lorentz model equation we should have used would have been derived using. Characteristics of electromagnetic waves in vacuum. Possible effects of electromagnetic fields emf on human health. Electromagnetic waves have constant velocity in vacuum and it is nearly equal to which is denoted by. The vector r denotes the location in space where the. Isbn 9789533073040, pdf isbn 97895351607, published 20110621. The electromagnetic wave is one of the four fundamental forces described in the standard model. Define divergence of a vector field n its significance 6.
Tata mcgrawhill education, oct 1, 2005 electromagnetic waves 580 pages. Some solutions to maxwells equations are electromagnetic waves. Substitute amperes law for a charge and currentfree region. Propagation of waves rit center for imaging science. The earths atmosphere, as medium introduces losses and impairments to the signal, which is generally not encountered in vacuum. An introduction to the theory of electromagnetic waves.
The visible electromagnetic spectrum goal the goal is to introduce the visible electromagnetic spectrum to students through use of materials readily available to most high school science classes. Applications of electromagnetic waves communications mobile phones. Each wavelength in the light produces a different color sensation in our eyes, from red to green to violet. Theory of electromagnetic wave propagation free space propagation of electromagnetic waves is often called radiofrequency rf propagation or simply radio propagation. This was the first prediction of radio waves, xrays, etc. Electromagnetic waves can be used in a variety of ways. Engineering electromagnetics and waves is designed for upperdivision college and university engineering students, for those who wish to learn the subject through selfstudy, and for practicing engineers who need an uptodate reference text. Hewson an introduction to the theory of electromagnetic waves longman group ltd. Possible effects of electromagnetic fields emf on human health 6 1. What is the wavelength of a microwave that has a frequency of 4. Maxwell was able to predict that electromagnetic waves can exist at any frequency, not just at the frequencies of visible light. We use them to communicate, cook, and for medical purposes.
Pdf propagation of electromagnetic waves in periodic. All electromagnetic waves travel at the same speed 300,000,000 metres per second, which is the speed of light. If a traveling wave is emitted by a planar source, then the points of constant phase form a plane surface parallel to the. Electromagnetic waves are created by oscillating electric and magnetic fields. Chapter maxwells equations and electromagnetic waves. Doppler lidars and radars, on the other hand, measure the change in c r r 1 0 0 r r 2 c r 2 2e t2 21 fundamental properties of electromagnetic waves 25 c02. Lei when an electromagnetic wave travels from one medium to another its speed changes either increases or. Current interest in these areas is driven by the growth in wireless and fiberoptic communications, information technology, and materials science. Possible effects of electromagnetic fields emf on human. The radio in your car receives the radio waves, decodes the information, and uses a speaker to change it back into a sound wave, bringing sweet music to your ears. Pearson engineering electromagnetics and waves, 2e umran. The human eye can only detect only a small portion of this spectrum called visible light. He was educated at the edinburgh academy and the university of edinburgh.
From maxwells equation to the wave equation consider a region of empty space in which there is no charge density and no current density, i. The very tiny portion of this spectrum that is visible to the human eye is the red thru violet light that we are able to see. The fields e and b and are perpendicular to the direction of propagation v em. Of course, this conclusion does not surprise anyone today, but imagine what a revelation it was in maxwells time. Doppler lidars and radars, on the other hand, measure the change in c r r 1 0 0 r r 2 c r 2 2e t2 21 fundamental properties of electromagnetic. Electromagnetic waves are transverse in nature as they propagate by varying the electric and magnetic fields such that the two fields are perpendicular to each other. He did often recount how his experience with understanding radiation theory from his solution of. The wavelength and frequency of electromagnetic waves vary from very long wavelengths to extremely short. Electromagnetic fields and waves dover books on physics. Laser or optical tweezers is an exciting new technique that allows manipulation of microscopic structures or of.
Electromagnetic waves summary the physics hypertextbook. Define curl of a vector field n its significance 7. The next four chapters discuss various aspects of optics, the science of light. Define gradient of a scalar field and its significance 5. The very tiny portion of this spectrum that is visible to the human eye is the red thru violet light that. Relationship of electric field and electric potential. He did often recount how his experience with understanding radiation theory from his. The topical organization of the text starts with an initial exposure to transmission lines and. The entire electromagnetic waves spectrum starts with radio waves at the lower frequencies and is named gamma and cosmic waves at the upper. Electromagnetic energy travels in waves and spans a broad spectrum from very long radio waves to very short gamma rays. Electromagnetic waves james clerk maxwell james clerk maxwell 18311879 was born in edinburgh, scotland, in the same year faraday discovered electromagnetic induction.
Electromagnetic waves properties of electromagnetic waves. Classical electromagnetic waves in free space before we can quantize the electromagnetic eld, we must develop some understanding of the classical electromagnetic eld. The electromagnetic spectrum introductionvisible light 1 instructors guide to lab no. Electromagnetic waves example problems what is the frequency green light that has a wavelength of 5. Unlike faraday, maxwell came from a welloff family. To see how a changing electric field gives rise to a magnetic field, let us consider the process of charging of a capacitor and apply amperes circuital law given by chapter 4 b. The total energy density for an electromagnetic wave is the sum of the two energy densities. Engineering electromagnetics and waves 2nd edition. The colors are present in the sunlight, in the sense that sunlight is a mixture of different.
Maxwells equations contain the wave equation for electromagnetic waves. The two components making up an electromagnetic wave are the. Kshetrimayum 3192014 polarization lossless medium good conductor fig. We deal with both normal and nonnormal angles of incidence. Rojansky argues that most students require a patient, careful discussion of fundamentals before undertaking advanced studies. The electromagnetic spectrum t e harrington middle school. A radio detects a different portion of the spectrum, and an xray machine uses yet another portion. Electromagnetics and applications mit opencourseware. The topical organization of the text starts with an initial exposure to transmission lines and transients on highspeed distributed. Electromagnetic radiation is greatest when charges accelerate at right angles to the line of sight. Ch 34 2, 6, 8, 12, 16, 17, 20, 25, 28, 35, 45, 47 since maxwells equations summarize everything we know about electricity and magnetism, they should lead us to an understanding of the properties of electromagnetic waves.
This means that although they appear to be very different, in fact theyre all made of the same kind of vibrations but at different. Electromagnetic waves would be capable of exerting forces on charges great distances from their source, and they might thus be detectable. Figure 255 electromagnetic waves and the line of sight. Zero radiation is observed when the charges accelerate along the line of sight. An electromagnetic wave is any disturbance in the electric and magnetic fields that propagates all electromagnetic waves propagate at the speed of light in a vacuum electromagnetic waves can have any wavelength or frequency. This type of information is recorded by polarimeters and polarimetric radars. Introduction to the electromagnetic spectrum science. All electromagnetic waves must travel in a vacuum with the same speed, a speed that we now call the speed of light. The electromagnetic spectrum introduction visible light 1 instructors guide to lab no. E and b are perpendicular to each other in a manner such that e. But the emerging problems of quantum electrodynamics caught his attention, and he never returned to classical electrodynamics while at harvard. Here we first introduce electromagnetic waves and some of their properties including their structure, energy, and momentum. This follows from the relativity fact that energy is equivalent. Introduction and types a wave is a transfer of energy through a medium from one point to another.
Pearson engineering electromagnetics and waves, 2e. Introduction classical electromagnetic waves in free space. Meaning of maxwells equations solution of maxwells equations introduction to electromagnetic theory electromagnetic radiation. These observations apply to electromagnetic waves of all frequencies. Maxwell calculated that electromagnetic waves would propagate at a speed given by the equation c 1 24. Engineering electromagnetics and waves provides engineering students with a solid grasp of electromagnetic fundamentals and electromagnetic waves by emphasizing physical understanding and practical applications.