Waves 2014


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Waves 2014

  1. 1. Waves Notes
  2. 2. Wave Types Transverse wave   • The motion of the medium is at right angles to the direction the wave is moving. Particles of the medium move up and down, but not horizontally.
  3. 3. Wave Types Longitudinal wave • The motion of the medium is parallel to the direction the wave is moving. Particles of the medium move horizontally, but not up and down.
  4. 4. Wave Characteristics: Amplitude - (wave height) • The maximum distance molecules are displaced from their rest position. • Amplitude indicates the energy of the wave.
  5. 5. Wave Characteristics: Wavelength • The distance between two consecutive crests of a wave. • Symbol for wavelength is the Greek letter lambda - λ
  6. 6. Wave Characteristics: Frequency • The number of complete waves per unit of time. • Hertz (Hz) - The units of wave frequency. • 1 Hz = 1 wave / sec
  7. 7. Wave Characteristics: Wave speed • Wave speed depends on the medium in which it travels. • In a given medium, the speed of a wave is constant. Wave speed is calculated by the equation: Speed = (frequency) (wavelength)
  8. 8. Wavelengths Graph
  9. 9. Sound: • Longitudinal waves composed of a series of compressions and rarefactions. • Mechanical – they must travel through a medium. • Sound waves cannot travel in the vacuum of space because there is no medium to transmit these mechanical waves.
  10. 10. Properties of Sound  Intensity • • The amount of energy in a wave. Intensity determines the amplitude of a wave. • • Intensity relates to the loudness of a sound - the greater the intensity, the louder the sound. Decibels - the units of intensity. • Sounds over 120 decibels will cause pain in the ears. • Ear damage can begin with exposure to sounds as low as 85 decibels.
  11. 11. Properties of Sound  Pitch • • • • • • • How low or high the sound is. The frequency of a wave determines its pitch. Pitch is related to frequency - the higher the frequency, the higher the pitch. The human ear can hear sounds ranging from 20 Hz to 20,000 Hz. Sounds over 20,000 Hz are called ultrasonic. Thunder has a low pitch with a frequency less than 50 Hz. A whistle has a high pitch with a frequency close to 1000 Hz.
  12. 12. Light: • Visible light is the portion of the electromagnetic spectrum that we can see. • As the full spectrum of visible light travels through a prism, the wavelengths separate into the colors of the rainbow because each color is a different wavelength.
  13. 13. Light: COLOR AND TEMPERATURE • As objects grow hotter, they radiate energy dominated by shorter wavelengths. • The color of stars tells scientists about their temperature.
  14. 14. Light: COLOR AND TEMPERATURE • Our Sun produces more yellow light than any other color because its surface temperature is 5,500°C. • The star Betelgeuse is cooler—about 3,000°C—and looks reddish. • The star Rigel is hotter—about 12,000°C—and looks blue.
  15. 15. Radio Waves • Radio waves have the longest wavelengths in the electromagnetic (EM) spectrum. • They range from the length of a football to larger than our planet.
  16. 16. Radio Waves: Radio Emissions in the Solar System • Astronomical objects that have a changing magnetic field can produce radio waves. • Radio telescopes look toward the heavens to view planets, comets, giant clouds of gas and dust, stars, and galaxies.
  17. 17. Radio Waves: Radio Emissions in the Solar System • By studying the radio waves originating from these sources, astronomers can learn about their composition, structure, and motion.