PHYS 1070 Lecture Notes - Lecture 4: Sine Wave, Longitudinal Wave, Sound
25 Mar 2015
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Phys1070: intro physics for life sci - lecture 4: acoustics. Particles oscillate about an equilibrium point as the waves move" forward. Transverse waves are perpendicular to the direction of wave propagation. Longitudinal wave are parallel to the direction of wave propagation. Its a wave of high molecular displacements within regions of high pressure (compressions) and low pressure (rarefactions) Regardless of how a sound is produced its rarely a single frequency and a perfect sine wave. Fundamental frequency (1st harmonic) but also many higher harmonics which can overlap to create all the sounds we can hear. Moves through time and space (has velocity v=f ) Is dependent on the medium it travels through (p=density) A: faster in water! more particles are closer together therefore its easier to transmit vibrations in a dense medium. Q: what are the corresponding wavelengths? (we know vair=340 m/s) A: at 20hz v=f =f/v = 340/20 = 17 m. At 20khz v=f =f/v = 340/20000 = 1. 7cm.
