Waves Physics Mr Berman Greece 2005 North Aegean

Waves Physics Mr. Berman Greece 2005, North Aegean Sea

• Waves and their characteristics • Velocity of a wave • Types of waves

Oscillation • Object moves back and forth about an equilibrium position.

Pulse: A single disturbance travelling through a medium. http: //www. dacc. edu/~qchen/P 102/labs/LAB 5. HTM

Wave Train (Travelling Wave or simply wave): • A series of pulses at regular intervals. http: //micromachine. stanford. edu/~hopcroft/Research/resonator_images/sin_mov 1. gif

Wave on a String • (Applet) http: //phet. colorado. edu/sims/wave-on-astring/wave-on-a-string_en. html

Graph of Displacement vs Time

Displacement vs Distance Traveled

Speed of a Wave, v v= d/t v = l/T v =lf

Types of Waves • Transverse • Longitudinal

Transverse The particles vibrate perpendicular to the direction of the wave's propagation (ex: waves along a string, electromagnetic waves).

Example: S Earthquake Wave http: //web. ics. purdue. edu/~braile/edumod/waves/Swave_files/image 001. gif

Longitudinal Waves • The particle displacement is parallel to the direction of wave propagation (ex: sound)

Torsional Waves • Video link on Web : Collapse of Takoma Narrows Bridge, Washington State, 1940 • http: //www. youtube. com/watch? v=sh. X 4 Q 0 QV 8 VI

Elliptical Waves Result when longitudinal and transverse waves are superpositioned. (ex: surface water waves)

Ocean Wave

Ocean Wave http: //www. pa. uky. edu/~crawford/phy 361_sp 10/home. html

Note • Waves transfer of energy from one point to another. • Waves do not transfer matter.

Types of Waves • Mechanical Waves • Electromagnetic Waves

Mechanical Waves require a medium. Examples: • Water waves( Tsunami) • Sound waves (v= 340 m/sec in air but varies for different media) • Earthquake waves

Electromagnetic Waves do not require a medium and can travel through the empty space (vacuum). Example: • Light from the sun travels through space and reaches us. Note: All EM waves have a speed through vacuum of 3 x 108 m/sec.

Problem 1 • What is the distance a sound wave in air traveled in 2 sec? Answer: 680 m/s

Problem 2 • What is the frequency of a light wave of wave length 550 x 10 -9 m? • Answer: 5. 5 x 10 14 Hz

Problem 3 • A SONAR (Sound Navigation and Ranging) sends a signal to the bottom of the ocean. The speed of sound in water is 1435 m/s. If the signal echo returned in 0. 4 sec, how deep was the water? • Answer: 287 m