3. Waves

    Cards (56)

    • Waves
      A transfer of energy, not the transfer of matter (Can be seen as a transfer of information such as sound waves)
    • Period
      How long it takes for a wave to pass/travel
    • Wavelength (λ)
      Unit: m
    • Wave speed (V)
      Unit: m/s
    • Frequency (F)
      Unit: Hz (Hertz)
    • MHz
      1,000,000 Hz (10^6)
    • Wave types

      • Transverse
      • Longitudinal
    • Transverse waves
      • Vibrations travel perpendicular to the direction of the wave
    • Longitudinal waves
      • Vibrations travel parallel to the direction of the wave
    • Crest
      Top of a transverse wave
    • Trough
      Bottom of a transverse wave
    • Amplitude
      Measured from the baseline to either the crest or trough
    • Wavelength
      Measured from one point to another identical point in the wave (crest to crest or trough to trough)
    • Compression
      Section where a longitudinal wave is close together
    • Rarefaction
      Section where a longitudinal wave is far apart
    • Frequency (f)
      How many waves are passing per second. One hertz = One wave a second
    • Doppler effect

      An apparent change in frequency is perceived when relative motion exists between the wave source and the receiver
    • As the sound wave source moves closer

      The frequency increases and becomes a higher frequency/pitch
    • As the sound wave source moves away

      The frequency decreases and the sound becomes a lower frequency/pitch
    • Light, a higher frequency/low wavelength
      The object will seem purple/blue
    • For light, a lower frequency/high wavelength

      The object will seem more red
    • Electromagnetic waves

      • Radio waves
      • Microwaves
      • Infrared radiation
      • Visible light
      • Ultraviolet
      • Gamma radiation
    • Radio waves

      Used mainly for communication
    • Microwaves
      Used for satellite communication and heating food
    • Infrared radiation
      Used for heating and to monitor temperature
    • Visible light

      Used for photography
    • Ultraviolet
      Used in fluorescent lamps
    • Gamma radiation

      Can be very useful for sterilising medical equipment and sterilising food
    • Radio Waves
      Have the lowest frequency
    • Infrared
      Can cause a heating effect by making surface molecules vibrate. Too much exposure can cause skin burns
    • Ultraviolet
      Can damage surface cells and cause blindness
    • Gamma rays

      Have the highest frequency which can cause cell mutation and tissue damage
    • Light can exhibit

      • Ray (e.g. reflection)
      • Wave (e.g. interference and diffraction)
      • Particle (e.g. photoelectric effect)
    • According to the concept of wave-particle duality in quantum mechanics, light exhibits both particle and wave nature, depending upon the circumstances
    • What can happen when light travels from one medium to another

      • Gets absorbed (absorption)
      • Bounces back (reflection)
      • Passes through or bends (refraction)
    • When light is incident on a plane mirror, most of it gets reflected, and some of it gets absorbed in the medium
    • The speed of light is a constant which is 2.998×10^8 m/s or approximately 3.0×10^8 m/s
    • A medium that is polished well without any irregularities on its surface will cause regular reflection of light. For example, a plane mirror. But even then, some light gets absorbed by the surface
    • The incident ray, reflected ray and the normal all lie in the same plane. Angle of incidence = Angle of reflection [∠i=∠r]
    • Waves have a frequency higher than the upper limit for human hearing – above 20,000 Hertz (Hz). Different species of animals have different hearing ranges. This explains why a dog can hear the ultrasound produced by a dog whistle, but humans cannot
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