Waves and Modern Physics PHY 123 - Spring 2012

Prof. Antonio Badolato ���Office: BL 158

Email: badolato@pas.rochester.edu

Course Web Site   http://www.pas.rochester.edu/~badolato/PHY_123/PHY_123.html  

Recitations:

Waves and Modern Physics, PHY 123 (Spring 2012)

Monday: 3.25 - 5.25 Imran (HYLAN 202), Tuesday: 3.25 - 5.25 Andrew (HYLAN 206),

4.50 - 7.50 Josh (B&L 270),

6:15 - 8.15 Andrew (B&L 269), Wednesday: 6.15 - 8.15 Andrew (B&L 315).

Prof. Antonio Badolato:

Wednesday, 1:45 p.m. - 2:45 p.m. room BL 158 TA Andrew Vigoren:

Thursday, 3:30 p.m. - 4:30 p.m, room BL 324

Office Hours:

Waves and Modern Physics, PHY 123 (Spring 2012)

Chapter 15 Wave Motion

All types of traveling waves transport energy.

A single wave pulse can be generated by a vibration. It is transmitted through internal forces in the medium.

Continuous waves start with vibrations, too. If the vibration is SHM, then the wave will be sinusoidal.

15-­‐1  Characteris.cs  of  Wave  Mo.on  

•  Amplitude, A

•  Wavelength, λ •  Frequency, f and period, •  Wave velocity,          

15-1 Characteristics of Sinusoidal (or Harmonic)Wave Motion

T =1f=2πω

Wave velocity   v = λ f = λT

= λω2π

Waves can move over large distances, but the medium itself has only a limited movement, oscillating about an equilibrium point as in SHM.  

The motion of particles in a wave can be either perpendicular to the wave direction (transverse) or parallel to it (longitudinal).

15-2 Types of Waves: Transverse and Longitudinal

Sound waves are longitudinal waves:

15-2 Types of Waves: Transverse and Longitudinal

Generation of longitudinal waves: Acoustic Waves

Waves can be a formed by a combination of longitudinal and transverse waves (like earthquakes waves). Both types can travel through solid material, but only longitudinal waves can propagate through a fluid—in the transverse direction, a fluid has no restoring force.

15-­‐2  General  Waves  

Transverse waves traveling through the body of the Earth: so-called S-waves

Waves can be a formed by a combination of longitudinal and transverse waves (like earthquakes waves). Both types can travel through solid material, but only longitudinal waves can propagate through a fluid—in the transverse direction, a fluid has no restoring force.

15-­‐2  General  Waves  

Longitudinal waves traveling through the body of the Earth: so-called P-waves

Surface waves are waves that travel along the boundary between two media (like water waves).

15-­‐2  General  Waves  

The velocity of a transverse wave on a cord is given by:

As expected, the velocity increases when the tension increases, and decreases when the mass increases.

15– 2 Wave velocity  

15– 2 Wave velocity  

The velocity of a longitudinal wave depends on the elastic restoring force of the medium and on the mass density.

or E is the elastic modulus B is the bulk modulus ρ is the density