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Electromagnetic Induction

Dive into the fascinating world of electromagnetic waves and forces in nature, from radio waves to gamma rays, with insights on their propagation, sources, and applications.

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Electromagnetic Induction

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  1. Electromagnetic Induction Electromagnetic Waves

  2. Propagation of Electromagnetic Waves • Electromagnetic waves have electric field and magnetic field components (at right angles to each other) • Radio waves have long wavelength, short frequency, and low energy • Gamma rays have short wavelength, high frequency, and high energy • Visible light is somewhere in the middle • Faraday’s law of induction - A changing magnetic field can induce a current • Coulomb’s law – electric field lines flow from positive to negative charges • Magnetic fields lines are closed loops • Ampère’s law – a magnetic field is created around a current-carrying wire

  3. Propagation of Electromagnetic Waves • James Clerk Maxwell – developed equations to describe the relationships between electric and magnetic fields in mid-1800s • Combined the research of Coloumb, Faraday, and Ampère • Hypothesized that a changing electric field should produce a magnetic field • Inverse of Faraday’s law • Described the wave formed by interactions of changing electric and magnetic fields as an electromagnetic wave • Predicted that light was electromagnetic • Not confirmed until 1887 by Heinrich Hertz • Transverse in nature – electric field is on one axis; magnetic field is on a second axis; wave travels on a third axis

  4. Propagation of Electromagnetic Waves • Electromagnetic Waves

  5. Propagation of Electromagnetic Waves • Electric and magnetic forces are aspects of a single force • Electromagnetic force • One of four fundamental forces in the universe • Gravitational • Electromagnetic • Weak Nuclear • Strong Nuclear • The weak force and the electromagnetic force were once part of a single force called the electroweak interaction • Electromagnetic force obeys an inverse-square law • Gets weaker based on the square of the distance from the source • Similar to sound and gravity

  6. Propagation of Electromagnetic Waves • All electromagnetic waves are produced by accelerating charges • Simplest source is an oscillating charged particle • Wave propogates itself as the changing electric field generates a changing magnetic field which generates a changing electric field • Electromagnetic radiation – the transfer of energy associated with an electromagnetic wave; it varies periodically and travels at the speed of light • High energy electromagnetic waves behave like a particle • Photon – a unit or quantum of light • A particle of electromagnetic radiation that has zero mass and carries a quantum (amount) of energy • Wave-particle duality of light – light has properties of both waves and particles • Low-energy photons behave more wavelike • Energy of a photon = Plank’s (or Planck’s) constant * frequency • E = h * f • Plank’s constant = 6.63 * 10-34 J*s

  7. Section 4 Electromagnetic Waves Chapter 20 The Sun at Different Wavelengths of Radiation

  8. Electromagnetic Spectrum • All electromagnetic waves are part of the electromagnetic spectrum • The all travel at the same speed (3.00 * 108 m/s in a vacuum) • Radio waves – longest wavelength, lowest frequency, lowest energy • Long wavelength is ideal for transmitting energy over long distances • TV and radio signals, radio telescopes • Microwaves – microwave ovens, satellite signals, cellphones, radar, telescopes • Wavelengths from 30cm to 1mm

  9. Electromagnetic Spectrum • Infrared – experience infrared as heat • Night vision goggles, remote controls, heat lamps, burglar-alarm systems • 1mm to 700nm • Visible light – what we see • Wavelengths range from 700nm (red light) to 400nm (violet light) • Ultraviolet (UV) – sunburns and suntans, sterilization of medical and scientific equipment, black lights, forensic investigations, telescopes • Certain materials fluoresce under ultraviolet • Flowers, rocks, black light posters, body fluids • Wavelengths from 400nm to 60 nm

  10. Electromagnetic Spectrum • X-Rays – high energy radiation • Medical and dental applications – used to view hard tissues • Security checks to examine baggage at airports or government offices • X-Ray emissions give the evidence of black holes • Wavelengths from 60nm to .0001nm • Gamma Rays – Very high energy • Radiation therapy in cancer treatments • Space telescopes • Wavelengths less than .0001nm

  11. Section 4 Electromagnetic Waves Chapter 20 The Electromagnetic Spectrum

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