physics 1

• Electromagnetic wave


  Waves created as a result of vibrations between an electric field and a magnetic field
• Production of electromagnetic waves

  Charge changes direction or speed
• Electric field


  The physical field that surrounds electrically-charged particles and exerts force on all other charged particles in the field, either attracting or repelling them
• Magnetic field


  A vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials
• Electrons are charged particles that can produce electric and magnetic fields
• Propagation of electromagnetic waves


  Changing magnetic field produces an electric field, and changing electric field produces a magnetic field
• Electromagnetic waves


  • Transverse waves without a medium (can travel through empty space)
• Light as a wave

  Light can be described as an electromagnetic wave
• Electromagnetic radiation has properties of waves but also can be thought of as a stream of particles
• Photoelectric effect


  When light is directed at a substance, it can knock electrons off of the substance
• Speed of electromagnetic waves

  300,000 kilometers per second or 3 x 10^8 m/s (the speed of light)
• Electromagnetic waves travel at a very fast speed and can go around the world 8 times in one second
• Electromagnetic wave theory is a theory that explains the nature and propagation of electromagnetic waves
• Proponents of electromagnetic wave theory

  • Hans Christian Oersted
  • André-Marie Ampère
  • Michael Faraday
  • James Clerk Maxwell
  • Heinrich Hertz
• Hans Christian Oersted


  • Discovered that electric current in a wire can deflect a magnetized compass needle, demonstrating the magnetic effect based on the direction of a current
• André-Marie Ampère


  • Made the revolutionary discovery that a wire carrying electric current can attract or repel another wire next to it that's also carrying electric current, formulated Ampère's law of electromagnetism
• Michael Faraday


  • Discovered electromagnetic induction, formulated the principle that a changing magnetic field produces an electric current
• James Clerk Maxwell


  • Developed equations that showed the relationship of electricity and magnetism, assumed that light was an electromagnetic wave and correctly deduced the finite velocity of light
• Heinrich Hertz


  • Proved the existence of radio waves in the late 1880s, showed experimental evidence of electromagnetic waves and their link to light
• Mechanical waves require a medium to propagate, while electromagnetic waves can propagate through a vacuum
• Electromagnetic waves propagate at 300,000,000 m/s (3 x 10^8 m/s) through a vacuum
• Hertz


  One cycle per second
• Heinrich Hertz


  • Proved the existence of radio waves in the late 1880s
  • Used two rods that served as a receiver and a spark gap as the receiving antennae
  • Showed experimental evidence of electromagnetic waves and their link to light
• Hertz showed in his experiments that these signals possessed all of the properties of electromagnetic waves
• Mechanical waves


  • Require a medium to propagate
  • Examples: water waves, earthquake waves, sound waves
• Light


  • Can be described as a wave of changing electric and magnetic fields that propagate outward from their sources
  • Do not require a medium to propagate
  • Propagate at 300,000,000 m/s (3 X 10^8 m/s) through a vacuum
• Electromagnetic waves


  • Transverse waves
  • Changing electric and magnetic fields oscillate perpendicular to each other and to the direction of the propagating waves
  • Magnetic fields generate each other through Faraday's Law of Induction and Ampere's Law of Electromagnetism
  • When the oscillating charge accelerates, the moving charge's electric fields change, too
• All matter contains charged particles that are always moving; therefore, all objects emit EM waves
• The wavelengths become shorter as the temperature of the material increases
• Radiant energy


  Also known as electromagnetic radiation (EMR), is energy transmitted without the movement of mass. Practically speaking, this is the energy found in electromagnetic waves, also known as light. Light is made of individual particles called photons, each carrying a small "packet" of energy
• EM waves are produced by accelerated or oscillating charge
• EM waves do not require any material or medium for propagation. But it does not mean that electromagnetic waves cannot travel through a medium
• All EM waves travel 300,000 km/sec or 3 X 10^8 m/s in space (speed of light- nature's limit!)
• EM waves usually travel SLOWEST IN SOLIDS and FASTEST IN GASES
• Electromagnetic Spectrum (EMS)


  The entire distribution of ELECTROMAGNETIC RADIATION according to frequency or wavelength. Although all electromagnetic waves travel at the speed of light in a vacuum, they differ at a wide range of FREQUENCIES, WAVELENGTHS, AND PHOTON ENERGIES
• Wavelength (λ)


  Distance from crest to crest (m)
• Frequency (f)


  Number of wavelengths that pass a given point in 1 s (Hertz or Hz)
• Photon Energy (E)


  1 Hz is equal to 6.626 × 10^-34 J and the Planck's constant in terms of eV is 4.14 × 10^-15 eV· s
• Frequency and energy


  Are directly proportional (Higher frequency, higher energy. Lower frequency, lower energy)
• Wavelength and energy


  Are inversely proportional (Shorter wavelength, higher energy. Longer wavelength, lower energy)