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Standing Wave / Resonant Frequency Lab

1. Go to essential-physics.com in a browser that is NOT Internet Explorer 2. Enter this code: 841 9439 3.Click on the Investigations “icon Scroll down and click on “15D: “Wavelength and Standing Waves” -

4. Scroll down and click on the “iPhysics”icon - - to launch the simulation -

The resonant frequency of an object is the frequency at which the object will support a standing wave. The frequency at which ½ standing wave is supported is called the fundamental frequency. The successive frequencies that will support increasing ½ multiples of standing waves are termed harmonic frequencies. Using the “wiggler” find up to eight resonant frequencies of your string. Complete the table below as you find various resonant frequencies. NOTE: Wave Speed (v)= Wavelength (λ) x Frequency (f), or v = λ•f


Harmonic

Number of Standing Waves

Frequency (Hz)

Wavelength (cm)

SnapShot

Wave Speed (cm/s)

1
















2
















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5
















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8
















Wavelength / Frequency Analysis

  1. What is the relationship between frequency and wavelength?

  2. What units does the product of frequency × wavelength have? What is the interpretation of this quantity… in other words, what does this unit mean?

  3. What is the relationship between harmonics and frequency?

  4. What is the relationship between harmonics and wavelength?

  5. According to your data, does the wave speed increase, decrease or remain constant?



  1. How could you control the frequency of a vibrating object through its wavelength? Describe at least two applications of this principle.

#s 7-10 are on the next page…


Bonus – Using your data, come up with one single a formula to calculate wavelength at any harmonic number if you are given or already know the length. Your formula must only contain wavelength, length of string and harmonic number

n , L , λ
Rubric Table = 10 pts. Each Analysis Question = 4 pts Bonus = 10 points


7. The string at the right is 1.5 meters long and is vibrating as the first harmonic. The string vibrates up and down with 33 cycles in 10.0 seconds. Determine the frequency, period, wavelength and speed for this wave.








8. The string at the right is 6.0 meters long and is vibrating as the third harmonic. The string vibrates up and down with 45 cycles in 10.0 seconds. Determine the frequency, period, wavelength and speed for this wave.






9. The string at the right is 5.0 meters long and is vibrating as the fourth harmonic. The string vibrates up and down with 48 cycles in 20.0 seconds. Determine the frequency, period, wavelength and speed for this wave.






10. The string at the right is 8.2 meters long and is vibrating as the fifth harmonic. The string vibrates up and down with 21 cycles in 5.0 seconds. Determine the frequency, period, wavelength and speed for this wave.





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