Physics

• Electromagnetic Waves


  • Radio wave
  • Microwave
  • Infrared
  • Visible light
  • Ultraviolet
  • X-ray
  • Gamma Ray
• Mechanical Waves

  • Propagate through a material medium with wave speed depending on the elastic and inertial properties of the medium
• Longitudinal Wave


  Movement of particles is parallel to the motion of the energy, displacement of the medium is in the direction in which the wave is moving
• Wavelength


  Distance between identical points in adjacent cycles of crests, measured in meters
• Compression

  Regions of high pressure due to particles being close together
• Frequency


  The number of waves passing a point in a certain time, measured in hertz (Hz)
• Types of Mechanical Waves


  1. Transverse Wave

  2. Longitudinal Wave
• Amplitude


  The height of the wave, amount of energy carried by a wave
• Mechanical Waves

  • Sound Waves
  • Water Waves
  • Earthquakes/Seismic Waves
• Wave


  A disturbance that travels through a medium and transfers energy from one place to another
• Transverse Wave

  Movement of particles is at right angles or perpendicular to the motion of the energy
• Types of wave

  • Mechanical Waves
  • Electromagnetic Waves
• Period

  Time for a particle on a medium to make one complete vibrational cycle, measured in seconds or minutes
• Electromagnetic Waves


  • Created as a result of vibrations between an electric field and magnetic field, do not need a medium for propagation
• Rarefaction

  Low pressure due to particles being spread further apart
• Electromagnetic waves


  • James Clerk Maxwell predicted waves could be propagated in space from one region to another due to varying magnetic and electric fields
• Value of Plank's constant is 6.63 x 10^-34 J-s
• Speed of light for electromagnetic waves is 3.00 x 10^8 m/s
• Wave properties


  Frequency and speed
• Energy of a photon is calculated using the equation E = hf
• Amplitude Modulation and Frequency Modulation

  • Electromagnetic waves are used to transmit information by modulating their amplitude, frequency, or phase
• Unit of frequency for electromagnetic waves is hertz (Hz), named in honor of Heinrich Hertz
• Radio waves have the longest wavelength in the electromagnetic spectrum and are used to transmit sound and picture information over long distances
• Electromagnetic waves are produced by perpendicular oscillations of magnetic and electric fields, classified by frequencies or wavelengths
• Heinrich Hertz


  • First to produce electromagnetic waves in the laboratory using an LC oscillator and a receiver, proving Maxwell's theory correct
• Calculating velocity of waves

  Velocity = Wavelength / Time
• The electromagnetic spectrum encompasses the entire range of electromagnetic radiation
• Marconi and Radio Communication

  • Guglielmo Marconi invented wireless communication in the 1890s, establishing the first transatlantic "wireless communication" in 1908
• Marconi established the first transatlantic "wireless communication"


  1908
• Microwave Ovens penetrate the food being heated, creating molecular friction which produces heat to cook it
• William Herschel in 1800 conducted an experiment measuring the difference in temperature between colors in the visible spectrum
• Radar Guns reflect back from oncoming vehicles and are detected by a receiver in the radar gun
• Amplitude Modulation

  Modulating electromagnetic waves by changing their amplitude to encode messages
• Frequency Modulation

  Modulating electromagnetic waves by changing their frequency to encode messages
• Thermal Imaging allows us to see infrared waves emitted by objects like humans and animals, measured in degrees Fahrenheit
• A television transmitter uses FM for audio and AM for video
• Frequency Modulation (FM)

  The carrier wave's frequency changes with the amplitude of the audio signal, amplifying it and sending it to a transmitting antenna for EM waves
• Marconi won the Nobel Prize for Physics


  1909
• Visible Light is a segment of the EM spectrum that the human eye can view, with wavelengths from 380 to 700 nm
• How Radars work

  The radar uses a focused microwave pulse to detect an object, likely a cloud, which is measured by bouncing back some of the energy, providing information about the object