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# The Wave Equation.

The Wave Equation. 7 August, 2014. Keywords Wavelength, lamda, amplitude, frequency, Hertz, kilohertz, megahertz, speed, metres, kilometres. All students should be able to: Define wave-speed, wavelength and frequency and recall the units. Most students should be able to:

## The Wave Equation.

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### Presentation Transcript

1. The Wave Equation. 7 August, 2014 Keywords Wavelength, lamda, amplitude, frequency, Hertz, kilohertz, megahertz, speed, metres, kilometres.

2. All students should be able to: Define wave-speed, wavelength and frequency and recall the units. Most students should be able to: Be able to use the wave equation. Some students should be able to: Be able to recall the wave equation and rearrange it for wave-speed, wavelength and frequency and recall the symbols for each. Outcomes

3. Quantity Symbol Unit m m Speed f f Frequency λ λ m/s m/s Wavelength v v Hz Hz Write a definition for speed, frequency and wavelength.

4. Your teacher will demonstrate to you how wave-speed, frequency and wavelength are related. See if you can come up with the relationship yourself. What happens to the wavelength when the frequency stays constant but the speed increases? Does it go up or down? What happens when the frequency increases but the speed stays the same? Demo time

5. How is wave speed calculated? These waves are travelling across the surface of a pond. The length of each wave is 0.25 m. Two waves pass the duck each second, so the frequency is 2 Hz. This means that the waves travel 0.5 m each second, so the speed of the waves is 0.5 m/s. From this example, the connection between speed, frequency and wavelength is: speed = frequency x wavelength 0.5 m/s=2 Hz x 0.25 m

6. What is the formula for wave speed? For any set of waves, the wave speed (v) can be calculated from the frequency (f) and wavelength ()using this formula: wave speed =frequency x wavelength v =f x  What are the units of speed, frequency and wavelength? • Wave speed is measured in metres per second (m/s). • Frequency is measured in hertz(Hz). • Wavelength is measured in metres (m).

7. Can I use a formula triangle? A formula triangle helps you to rearrange a formula. The formula triangle for wave speed (v), frequency (f) and wavelength () is shown below. Cover the quantity that you are trying to work out, which gives the rearranged formula needed for the calculation. So to find frequency (f), cover up f… …which gives the formula…   v f =  x

8. Calculating wave speed – example These waves are rippling across a pond. The frequency of the waves is 0.2 Hz and the length of each wave is estimated at 0.15m. What is the wave speed? wave speed = frequency x wavelength = 0.2 Hz x 0.15 m = 0.03 m/s

9. Kilo means: One thousand times: 1000 x Mega means: One Million times: 1000 000 x km = kilometres = 1000 m MHz = MegaHertz = 1000 000 Hz GHz = GigaHertz = 1000 000 000 Hz Units Take care

10. Work with the person next to you and see how many of the questions you can do using the wave equation. They will give you great practise at using it. Your teacher will set you a time limit of up to 30 mins TASK – Wave equation worksheet

11. All students should be able to: Define wave-speed, wavelength and frequency and recall the units. Most students should be able to: Be able to use the wave equation. Some students should be able to: Be able to recall the wave equation and rearrange it for wave-speed, wavelength and frequency and recall the symbols for each. Outcomes – How have you done? Look below and rate yourself:

12. Wave speed problems

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