EMS science study

• Waves


  A disturbance that moves through matter or space
• Types of waves

  • Mechanical waves
  • Electromagnetic waves
• Mechanical waves


  • Must travel through a medium, and are created when a source of energy causes the medium to vibrate
  • Transverse and Longitudinal waves are types of mechanical waves
  • Examples: water, slinky, human wave at a game
• Electromagnetic waves


  • Do not need a medium to travel through
  • Electromagnetic waves are transverse waves
  • Examples: light, radio, microwaves, IR, visible light, UV, X-ray, Gamma
• Transverse waves


  Particles of the medium move at right angles (up & down)
• Medium


  Carries a mechanical wave
• Energy


  Carries a wave (mechanical or electromagnetic)
• Energy put into a wave

  Affects the speed of a wave
• Factors affecting wave speed

  • Density of medium
  • Elasticity of medium
• Density


  A wave moves more slowly through a denser medium due to the amount of inertia it must overcome
• Elasticity


  The ability of a medium to return quickly to its original shape after being disturbed
• Parts of a transverse wave

  • Amplitude
  • Wavelength
  • Crest
  • Trough
• Amplitude


  Corresponds to the amount of energy in the wave
• Solving for speed, frequency or wavelength

  1. Speed = Wavelength x Frequency

  2. Frequency = Speed / Wavelength

  3. Wavelength = Speed / Frequency
• Wave with wavelength 0.5 m and frequency 120 Hz

  • Speed = 60 m/s
• Wave with speed 75 m/s and wavelength 0.6 m


  • Frequency = 125 Hz
• Frequency and wavelength with constant speed

  If frequency increases, wavelength decreases. If frequency decreases, wavelength increases.
• Speed of light in a vacuum

  3.00 x 10^8 m/s
• Light travelling outside a vacuum

  Speed decreases as light travels through different mediums
• Photons


  In an atom, electrons can get excited and move to outer orbitals. When the electron goes back to the inner orbital, energy is given off as photons of light.
• Energy and wave


  The higher the amplitude, the greater the energy. Also, there is more energy with increased frequency and shorter wavelength.
• Light as a wave

  • Light is a transverse wave, with an electric field and a magnetic field (electromagnetic waves)
  • Light does not require a medium to travel through
• Parts of the electromagnetic spectrum

  • Radio
  • Microwaves
  • Infrared
  • Visible light
  • Ultraviolet
  • X-rays
  • Gamma rays
• Uses of different parts of the electromagnetic spectrum

  • Radio - transmit radio/TV signals, GPS, MRI, radar
  • Microwaves - cell phones, microwave ovens
  • Infrared - thermal imaging, heat lamps
  • Visible light - light we see, rainbows
  • UV light - Sun's light, can be harmful to humans, helps produce Vitamin D
  • X-rays - pass through skin, not bone
  • Gamma - found in nuclear reactions
• Trends in the electromagnetic spectrum

  • As energy increases, frequency increases
  • As wavelength increases, frequency decreases
• Visible light spectrum in order

  • Red
  • Orange
  • Yellow
  • Green
  • Blue
  • Indigo
  • Violet
• Primary colors of light

  Red, Blue, Green
• Color perception


  Humans have photoreceptors that perceive the three primary colors and additive colors using these three in various combinations
• Seeing color


  Red is being reflected and all other colors in the spectrum are being absorbed
• Emission spectra


  Have specific colored lines in their spectra like a fingerprint, can be used to identify elements
• Continuous spectra

  Come from white light, ROYGBIV can be seen
• Uses of emission and continuous spectra
• Law of Reflection

  When light rays fall on a smooth surface, like a plane mirror, the angle of reflection is equal to the angle of incidence
• Diffraction

  The behavior that you see when a wave encounters an obstacle or must pass through a small opening
• refraction- the redirection of a wave as it passes from one medium to another