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Waves

Waves. 10 August, 2014. Keywords Wavelength, amplitude, frequency, Hertz, speed, transverse, peak, trough, longitudinal, compression, rarefaction. All students should be able to: Describe what a wave is. Most students should be able to:

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Waves

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  1. Waves 10 August, 2014 Keywords Wavelength, amplitude, frequency, Hertz, speed, transverse, peak, trough, longitudinal, compression, rarefaction.

  2. All students should be able to: Describe what a wave is. Most students should be able to: Draw labelled diagrams that show the wavelength, amplitude, peak and trough and be able to define the frequency and speed of a wave. Be able to describe the properties of transverse and longitudinal waves. Some students should be able to: Use models to explain the differences between transverse and longitudinal waves. Outcomes

  3. What is a wave? A wave is a series of disturbances that are the same distance from each other and transfer energyfrom one place to another. There are 2 types of wave: Transverse Longitudinal Task: Copy the slide and then come over to watch the demo of a slinky

  4. We have seen how we can model waves with a slinky; We can also model waves with students. What does each student represent? Could you explain the differences between transverse and longitudinal waves using this model? What type of wave is sound? – How could you use this model to show how sound travels at different speeds through solids, liquids and gases? STUDENT MODELLING

  5. 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.

  6. Simulation of a transverse wave

  7. What are the parts of a transverse wave? Certain parts of a transverse wave have special names. Water waves and electromagnetic waves, such as light, are examples of transverse waves. wavelength peak amplitude wavelength amplitude trough wavelength The amplitude of any wave is the maximum distance a point moves from its rest position. The wavelength is the same whichever two matching points are used to measure this distance. The symbol used to represent wavelength is .

  8. Investigating transverse waves

  9. 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.

  10. Simulation of a longitudinal wave

  11. What are the parts of a longitudinal wave? Certain parts of a longitudinal wave have special names. wavelength compression rarefaction wavelength Sections that are pushed together are called compressions and that are stretched out are called rarefactions. Sound waves are longitudinal waves. When someone speaks, the air particles vibrate as a longitudinal wave and so compressions and rarefactions are formed in the air.

  12. Frequency of transverse waves The frequency is the number of waves passing any point each second. • frequency = number of waves past a point / time • frequency is measured in hertz (Hz) • 1 wave per second = 1 Hz If this set of transverse waves pass a point in one second, what is the frequency? 4 Hz

  13. 2nd – Get a worksheet, ruler and goggles and do the answers to the worksheet in your exercise book. Do NOT write on the sheets please. PRACTICAL TIME!! – 1st finish the diagrams below: wavelength compression rarefaction wavelength wavelength peak amplitude wavelength amplitude trough wavelength

  14. Procedure and Questions 1. Place the ruler on the table so that half of it hangs over the edge. 2. Hold the ruler firmly against the table, and twang the end of the ruler. Listen to the sound it makes. 3. If more of the ruler were hanging over the edge of the table when you twanged it, how do you think the sound would be different? Why? 4. Test your answer to number 3. Describe what happened. 5. If less of the ruler were hanging over the edge of the table, how do you think the sound would be different? Why? 6. Test your answer to number 5. Describe what happened. 7. Draw pictures of the three positions of the ruler. Then, draw arrows or other symbols to show how the sound changed in each case. Finally, use the names of the properties of waves to label your diagrams and help describe what happened during this activity. Properties • Longitudinal• Amplitude • Wavelength • Frequency PRACTICAL TIME – The BIG Q: How can we describe what waves are? In your description: ALL should describe what a wave is. MOST should draw a labelled diagram of the type of waves coming off describing how they are different. SOME should explain how you could model these waves in some other way.

  15. Transverse or longitudinal waves?

  16. Frequency of waves – activity

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