# Waves and Sound: page 3

• AP Physics 1: Waves 14: Diffraction
• AP Physics 1: Sound 1: Speed of Sound
• AP Physics 1: Sound 2: Organ Pipes Both Ends Open & One End Closed
• AP Physics 1: Sound 3: Air Column Resonance & Speed of Sound Lab Problem
• I don’t know why there is music in this video either. Perhaps the video-editing crew was not paying attention. But why did I choose this video to use? Because the other lab or demonstration videos I looked at used methods that are not correct enough for students to receive full credit on the AP Physics B exams. Therefore, I rather use the video that provides very good data without the not-very-correct methods. So, please try to listen to the tuning fork sound and ignore the music. The first 10 cm location for each tuning fork is meant to show you what it sounds like without resonance. I think the 1st tuning fork is a keyboard/piano C of 512 Hz; and I think the 2nd tuning fork is a keyboard/piano F, 682.6Hz. Air Resonance with Water Column 水柱式氣柱共鳴實驗器 https://www.youtube.com/watch?v=WktrxzfXNn
• We can also change the speed of sound by changing the type of gas in a tube, because the speed of sound in a gas is closely related to the root-mean-square speed. ½ mvrms2 = (3/2) kT, so for gas with lighter molecules, the root-mean-square speed is faster, so the speed of sound in the gas is faster. v = fλ: Because the vocal cavity of a person stays the same, the resonant wavelength stays the same. Therefore, when wave speed increases, the resonant frequencies get higher. MythBusters - Fun With Gas http://www.youtube.com/watch?v=d-XbjFn3aqE
• Waves and Sound: page 1 (Waves 1 to 8: Waves, periodic waves, reflection, refraction)
• Waves and Sound: page 2 (Waves 9 to 13: Interference, resonance, standing wave)
• Waves and Sound: page 3 (Waves 14 to 15: Diffraction, multiple-choice question & Sound 1 to 3: Speed of sound, organ pipes)
• Waves and Sound: page 4 (Sound 4 to 8: Beats, Doppler effect, shock wave, multiple-choice questions)