{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Chapter 17 - Chapter 17 Waves II Part 1 Acoustic Waves...

Info icon This preview shows pages 1–11. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 17 Waves II Part 1
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Acoustic Waves Longitudinal waves - the particles oscillate in the direction of the wave propagation. There are regions of compression and expansion. A medium is required for the waves to propagate (we cannot hear in vacuum, cosmic space) Wave front : a set of particles that oscillate with the same phase. Wave rays : geometrical lines perpendicular to the wave fronts. They show the direction of wave propagation.
Image of page 2
Examples Audible acoustic waves (sound waves): Infra sound: f<20Hz Ultra sound: f>20kHz Seismic waves (not all seismic waves): small f<20Hz Audible sound Ultrasound Infrasound 20Hz 20kHz f<20Hz f>20kHz
Image of page 3

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Using a Tuning Fork to Produce a Sound Wave A tuning fork will produce a pure musical note As the tines vibrate, they disturb the air near them As the tine swings to the right, it forces the air molecules near it closer together This produces a high density area in the air This is an area of compression
Image of page 4
Using a Tuning Fork, cont. As the tine moves toward the left, the air molecules to the right of the tine spread out This produces an area of low density This area is called a rarefaction
Image of page 5

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Using a Tuning Fork, final As the tuning fork continues to vibrate, a succession of compressions and rarefactions spread out from the fork A sinusoidal curve can be used to represent the longitudinal wave Crests correspond to compressions and troughs to rarefactions
Image of page 6
What is happening?
Image of page 7

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
The speed of sound The speed of a traveling wave on a string: The speed of sound B bulk modulus of the material (rigidity) ρ - density of material It takes time for the sound to travel The speed of sound depends on the properties of the material only! υ = τ μ υ = B ρ Elastic property Elastic property Inertia Inertia
Image of page 8
Some examples Gases: Air (0 o C) 331 m/s Air (20 o C) 343 m/s Helium 965 m/s Hydrogen 1284 m/s Liquids: Water (0 o C) 1402 m/s Water (20 o C) 1482 m/s Seawater 1522 m/s Solids: Aluminum 6420 m/s Granite 6000 m/s As the properties of the materials change with temperature, so does the speed of sound!
Image of page 9

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Example problem: Earthquakes generate both transverse waves (S) and longitudinal waves (P). The speed of the S waves is about 4.5 km/s and that of P waves 8 km/s . A seismograph detects the first S wave some 3 min after the first P wave. How far is the Earthquake if the waves travel on a straight line?
Image of page 10
Image of page 11
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern