Electromagnetic waves are produced by

Summary • Describe the electric and magnetic waves as they move out from a source, such as an AC generator. • Explain the mathematical relationship between the magnetic field strength and the electrical field strength. • Calculate the maximum strength of the magnetic field in an electromagnetic wave, given the maximum electric field strength. We can get a good understanding of electromagnetic waves (EM) by considering how they are produced. Whenever a current varies, associated electric and magnetic fields vary, moving out from the source like waves. Perhaps the easiest situation to visualize is a varying current in a long straight wire, produced by an AC generator at its center, as illustrated in Figure 1. This long straight gray wire with an AC generator at its center becomes a broadcast antenna for electromagnetic waves. Shown here are the charge distributions at four different times. The electric field ( E) propagates away from the antenna at the speed of light, forming part of an electromagnetic wave. The electric field ( ) shown surrounding the wire is produced by the charge distribution on the wire. Both the and the charge distribution vary as the current changes. The changing field propagates outward at the speed of light. There is an associated magnetic field ( ) which propagates outward as well (see Closer examination of the one complete cycle shown in , there is the maximum separation of charge, with negative charges at the top and positive charges at the bottom...

https://phys.libretexts.org/@app/auth/3/login?returnto=https%3A%2F%2Fphys.libretexts.org%2FBookshelves%2FUniversity_Physics%2FBook%253A_University_Physics_(OpenStax)%2FBook%253A_University_Physics_II_-_Thermodynamics_Electricity_and_Magnetism_(OpenStax)%2F16%253A_Electromagnetic_Waves%2F16.02%253A_Maxwells_Equations_and_Electromagnetic_Waves Expand/collapse global hierarchy • Home • Bookshelves • University Physics • Book: University Physics (OpenStax) • University Physics II - Thermodynamics, Electricity, and Magnetism (OpenStax) • 16: Electromagnetic Waves • 16.2: Maxwell’s Equations and Electromagnetic Waves Expand/collapse global location Learning Objectives By the end of this section, you will be able to: • Explain Maxwell’s correction of Ampère’s law by including the displacement current • State and apply Maxwell’s equations in integral form • Describe how the symmetry between changing electric and changing magnetic fields explains Maxwell’s prediction of electromagnetic waves • Describe how Hertz confirmed Maxwell’s prediction of electromagnetic waves James Clerk Maxwell (1831–1879) was one of the major contributors to physics in the nineteenth century (Figure \(\PageIndex\): James Clerk Maxwell, a nineteenth-century physicist, developed a theory that explained the relationship between electricity and magnetism, and correctly predicted that visible light consists of electromagnetic waves. Maxwell’s Correction to the Laws of Electricity and Magnetism The four basic l...

[ "article:topic", "authorname:openstax", "gamma ray", "electromagnetic spectrum", "infrared radiation", "microwaves", "radar", "radio waves", "thermal agitation", "ultraviolet radiation", "visible light", "x-ray", "infrared radiation (IR)", "IR", "ultraviolet radiation (UV)", "UV", "amplitude modulation (AM)", "amplitude modulation", "AM", "extremely low frequency (ELF", "extremely low frequency", "ELF", "carrier wave", "frequency modulation (FM)", "frequency modulation", "FM", "TV", "very high frequency (VHF)", "very high frequency", "VHF", "ultra-high frequency (UHF)", "ultra-high frequency", "UHF", "license:ccby", "showtoc:no", "program:openstax", "licenseversion:40", "source@https://openstax.org/details/books/college-physics" ] Learning Objectives By the end of this section, you will be able to: • List three “rules of thumb” that apply to the different frequencies along the electromagnetic spectrum. • Explain why the higher the frequency, the shorter the wavelength of an electromagnetic wave. • Draw a simplified electromagnetic spectrum, indicating the relative positions, frequencies, and spacing of the different types of radiation bands. • List and explain the different methods by which electromagnetic waves are produced across the spectrum. 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 wil...

https://phys.libretexts.org/@app/auth/3/login?returnto=https%3A%2F%2Fphys.libretexts.org%2FBookshelves%2FConceptual_Physics%2FIntroduction_to_Physics_(Park)%2F04%253A_Unit_3-_Classical_Physics_-_Thermodynamics_Electricity_and_Magnetism_and_Light%2F11%253A_Light%2F11.03%253A_Production_and_Properties_of_Electromagnetic_Waves Expand/collapse global hierarchy • Home • Bookshelves • Conceptual Physics • Introduction to Physics (Park) • Unit 3: Classical Physics - Thermodynamics, Electricity and Magnetism, and Light • Chapter 11: Light • 11.3: Production and Properties of Electromagnetic Waves Expand/collapse global location Learning Objectives • Describe the electric and magnetic waves as they move out from a source, such as an AC generator. • Describe the momentum carried by electromagnetic waves and its relationship to radiation pressure. We can get a good understanding of electromagnetic waves(EM) by considering how they are produced. Whenever a current varies, associated electric and magnetic fields vary, moving out from the source like waves. Perhaps the easiest situation to visualize is a varying current in a long straight wire, produced by an AC generator at its center, as illustrated in Figure \(\PageIndex\)) which propagates outward as well (see Closer examination of the one complete cycle shown in As the process continues, the charge separation reverses and the field reaches its maximum downward value, returns to zero, and rises to its maximum upward value at the end...

[ "article:topic", "Electromagnetic waves", "authorname:openstax", "Electric field", "Magnetic Field", "amplitude", "transverse wave", "wavelength", "frequency", "Magnetic field strength", "Electric field strength", "standing wave", "resonant", "oscillate", "license:ccby", "showtoc:no", "program:openstax", "licenseversion:40", "source@https://openstax.org/details/books/college-physics" ] Learning Objectives By the end of this section, you will be able to: • Describe the electric and magnetic waves as they move out from a source, such as an AC generator. • Explain the mathematical relationship between the magnetic field strength and the electrical field strength. • Calculate the maximum strength of the magnetic field in an electromagnetic wave, given the maximum electric field strength. We can get a good understanding of electromagnetic waves (EM) by considering how they are produced. Whenever a current varies, associated electric and magnetic fields vary, moving out from the source like waves. Perhaps the easiest situation to visualize is a varying current in a long straight wire, produced by an AC generator at its center, as illustrated in Figure \(\PageIndex\) reveals the periodic nature of the generator-driven charges oscillating up and down in the antenna and the electric field produced. At time \(t = 0\), there is the maximum separation of charge, with negative charges at the top and positive charges at the bottom, producing the maximum magnitude of the electric field...