AP Physics Waves Pt 2

Mechanical vs. Electromagnetic Mechanical waves: require a medium Ex: Sound Electromagnetic waves: no medium Ex: light, microwaves, UV rays

Electromagnetic spectrum

Sound Waves Longitudinal waves that travel through air End Slide Sound Waves Longitudinal waves that travel through air Loudness refers to how much amplitude or energy a sound wave is carrying; measured in decibels Pitch is the perceived frequency (proportional but not directly) as interpreted by your ear/brain

Producing Sound

How The Ear Works

Range of Hearing

Sound Interactive Simulation End Slide Sound Interactive Simulation PhET – Sound Simulation http://phet.colorado.edu/en/simulation/sound “Measure” – Speed of Sound with 𝒗= 𝒅 𝒕 𝒂𝒏𝒅 𝒗=𝝀𝒇 “Two Source Interference” “Listen with Varying Air Pressure” – Vacuum Pump and Bell Jar

End Slide Sound Interference Sound waves interfere in the same way that other waves do in space. Constructive Destructive

The Doppler Effect This apparent change in frequency of a wave due to the motion of the source (or receiver) is called the Doppler effect. The greater the speed of the source, the greater will be the Doppler effect. As a wave source approaches, an observer encounters waves with a higher frequency. As the wave source moves away, an observer encounters waves with a lower frequency.

Doppler Effect http://www.lon-capa.org/~mmp/applist/doppler/d.htm End Slide Doppler Effect http://www.lon-capa.org/~mmp/applist/doppler/d.htm

The Doppler Effect, Big Bang Theory Style BBT

Breaking the Sound Barrier

Uses of Doppler Effect Echolocation (Bats and Dolphins) Weather End Slide Uses of Doppler Effect Echolocation (Bats and Dolphins) Weather Submarine Police Radar Expanding Universe Hydrogen Spectrum

End Slide Resonance Chamber A standing wave is produced inside of a chamber or tube with a specific length The number of nodes and antinodes determine the wavelength and frequency of the sound being produced

Resonance Chamber Harmonics (Open at both ends) Harmonics End Slide Resonance Chamber Harmonics (Open at both ends) Harmonics (Closed at One end)

End Slide Resonance Example Nodes are at closed ends and antinodes are at open ends From a node to an antinode (or vice versa) is 1/4th of a wavelength. Also…

End Slide Resonance Example Every half wavelength of distance will be another antinode and node Therefore, the same frequency will resonate again. For example…

Speed of Sound (Example 1 - E) End Slide Speed of Sound (Example 1 - E) An “E” is a 1.04 m wavelength sound wave. The tuning fork of an E note has a frequency of 320 Hz is stamped on it v = fl = (320 Hz)*(1.04 m) = 333 m/s

Resonance Tube