Activity 4 - Standing Waves in Tubes

Activity objectives

A. To understand the formation of a standing wave in tubes based on the standing wave on a string using a simulation. 

B. To determine the speed of sound in air using a closed tube.

C. To determine the resonance frequency at a fixed closed tube length.

⭐️ PART A : To understand the formation of a standing wave in tubes based on the standing wave on a string using a simulation. 

1. Draw the displacement profile of the first, 2nd and 3rd harmonics of standing waves along a string of length L.

2. Draw the displacement profile and pressure fluctuation profile of the standing wave in the following cases. Subsequently, determine in which n is the harmonic (https://physlets.org/pp/oscillations_waves/sound/default.html)

i. Solve problem 18.12

ii. Solve problem 18.13

iii. Solve problem 18.14

iv. Solve problem 18.15

3. Find the relation between harmonics and wavelength of the standing waves in open and closed tubes.

⭐️ Part B : To determine the speed of sound in air using a closed tube.

1. Differentiate between closed and open tubes.

2. You should have watched the following YouTube (https://www.youtube.com/watch?v=xrF7ZmBG-9U). Otherwise, please revise after this activity.

3. Generate 440 Hz sound using the app. Bring it close to the tube ends (at the resonance tube opening, as shown below).

4. Adjust the water level until you hear the loudest sound. Record the length of the air column. Repeat at least three times to get the average length.

5. Calculate the sound velocity in the air

⭐️ PART C : To determine the resonance frequency at a fixed closed tube length.

1. The theoretical value of sound velocity in air is 343 m/s. Calculate the resonance frequency if the closed tube length is 0.30 m

2. Verify your answer experimentally.