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Waves

Waves. Do Now Read pages 124-125. Learning today. What is a wave? Longitudinal and transverse waves Amplitude A , wavelength λ , frequency f and period of a wave T The relationship between frequency and period The wave equation v = f λ Homework due Monday 9 th April 2012

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Waves

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  1. Waves Do Now Read pages 124-125

  2. Learning today • What is a wave? • Longitudinal and transverse waves • Amplitude A, wavelength λ, frequency f and period of a wave T • The relationship between frequency and period • The wave equation v =fλ • Homework due Monday 9th April 2012 • Amplitude, frequency and wavelength

  3. What is a wave? YouTube - Water bubble in Space (zero gravity) http://www.youtube.com/watch?v=xUnadiyPTks

  4. Waves Waves can transfer energy and information without a net motion of the medium through which they travel. They involve vibrations (oscillations) of some sort.

  5. Waves Waves can transfer energy and information without a net motion of the medium through which they travel. They involve vibrations (oscillations) of some sort. Can you do something very boring and traditional……… Can you copy this please?

  6. Rays Rays highlight the direction of energy transfer.

  7. What do transverse waves look like? A Slinky can be used to model transverse waves, by moving one end of the Slinky up and down. coils vibrate up and down source moves up and down direction of wave The wave travels away from the source. The direction of the wave is at right angles to the movement of the source. In a transverse wave, the coils do not travel horizontally, each coil of the Slinky just vibrates up and down.

  8. Transverse waves The oscillations are perpendicular to the direction of energy transfer. peak Direction of energy transfer oscillation trough

  9. Transverse waves • Water ripples • Light • On a rope/slinky • Earthquake

  10. Investigating transverse waves

  11. Longitudinal waves The oscillations are parallel to the direction of energy transfer. Direction of energy transfer oscillation

  12. What do longitudinal waves look like? A Slinky can be used to model longitudinal waves, by moving one end of the Slinky left and right. source moves left and right coils vibrate left and right direction of wave The wave travels away from the source.The direction of the wave is parallel to the movement of the source. In a longitudinal wave, the coils do not travel horizontally, each coil of the Slinky just vibrates left and right.

  13. Longitudianl waves compression rarefraction Certain parts of a longitudinal wave have special names. Sections that are pushed together are called compressions and that are stretched out are called rarefactions.

  14. Longitudinal waves • Sound • Slinky • Earthquake

  15. Wave measurements

  16. Amplitude - A The maximum displacement from the mean position. amplitude

  17. Period - T The time taken (in seconds) for one complete oscillation. It is also the time taken for a complete wave to pass a given point. One complete wave

  18. Frequency - f The number of oscillations in one second. Measured in Hertz. 50 Hz = 50 vibrations/waves/oscillations in one second.

  19. Frequency of waves – activity

  20. Period and frequency Period and frequency are reciprocals of each other f = 1/T T = 1/f

  21. Wavelength - λ The length of one complete wave. wavelength

  22. Wave speed - v The speed at which the wave fronts pass a stationary observer. 330 m.s-1 YouTube - Bill Nye the Science Guy - 51: Waves 1/3

  23. Transverse or longitudinal waves?

  24. Some example wave equation questions • A water wave has a frequency of 2Hz and a wavelength of 0.3m. How fast is it moving? • A water wave travels through a pond with a speed of 1m/s and a frequency of 5Hz. What is the wavelength of the waves? • The speed of sound is 330m/s (in air). When Dave hears this sound his ear vibrates 660 times a second. What was the wavelength of the sound? • Purple light has a wavelength of around 6x10-7m and a frequency of 5x1014Hz. What is the speed of purple light?

  25. The Wave Equation v =fλ v = speed (m/s) λ = wavelength (m) f = frequency (Hz) v f λ x

  26. Some example wave equation questions • A water wave has a frequency of 2Hz and a wavelength of 0.3m. How fast is it moving? • A water wave travels through a pond with a speed of 1m/s and a frequency of 5Hz. What is the wavelength of the waves? • The speed of sound is 330m/s (in air). When Dave hears this sound his ear vibrates 660 times a second. What was the wavelength of the sound? • Purple light has a wavelength of around 6x10-7m and a frequency of 5x1014Hz. What is the speed of purple light? 0.6m/s 0.2m 0.5m 3x108m/s

  27. Wave equation questions v λ f x

  28. Let’s try some questions! Page 125 (all the questions) and page 136 questions 1 and 4.

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