# PHYS16 – Lecture 34 Waves December 3, 2010 “Interference is much clearer in HD”

## Presentation on theme: "PHYS16 – Lecture 34 Waves December 3, 2010 “Interference is much clearer in HD”"— Presentation transcript:

PHYS16 – Lecture 34 Waves December 3, 2010 “Interference is much clearer in HD”

Outline for Oscillations Simple Harmonic Motion – Position, Velocity, Acceleration – Force – Energy – Phase – Damping – Resonance Waves – Mechanical waves – Interference – Standing waves

Mechanical Waves

A propagating oscillation that moves through a medium Transverse – water waves Longitudinal – sound waves

Mechanical Waves Waves use at least 1-3 space dimensions and time… – Ex. – Water waves propagate in x, move “up and down” in y, and change position with time – Ex. – Sound waves propagate in x, move “up and down” in x, and change position with time

Wave Properties Period – T high period medium period low period

Wave Properties Period – Wavelength and Wave number – http://seagrant.uaf.edu/marine-ed/curriculum/images/stories/grade7/wave.jpg

Wave Properties Period – Wavelength and Wave number – http://eqseis.geosc.psu.edu/~cammon/HTML/Classes/IntroQuakes/Notes/Images_specific/wave_def.gif

Wave Properties Period – Wavelength and Wave number – Wave speed – http://eqseis.geosc.psu.edu/~cammon/HTML/Classes/IntroQuakes/Notes/Images_specific/wave_def.gif

Mechanical Wave – Position of Particle Plane Wave Higher Dimension Wave

Ripple Tank Simulation

Example Question 1 PhET website

Example Question 2 PhET website

Example Question 2 PhET website Speed = Period = Wave number = Wavelength = 330 m/s 0.0038 s 5.0m -1 1.25 m

Example Question 3 Sand is placed on the vibrating plate below. Which apparatus is vibrating the plate with the highest wave number?

Wave on a String

You can generate a wave on a string by pulsing sting with your hand Speed of pulse/wave is related to tension in string and mass density of string PhET website

Propagation of Pulse If you advance the movie one frame point A will move… (higher, lower, right, left)? If generate new pulse but more quickly than first then it will be… (same, wider, narrower)? If generate new pulse but move hand higher than first then it will be… (same, taller, shorter)? If generate new pulse with rope tightened then pulse will be… (same, faster, slower)? PhET website

Wave on String Simulation PhET website

Example Question PhET website

Superposition, Interference, and Standing Waves

Superposition and Interference Superposition - When two stimuli overlap they will superimpose, or the new stimulus will be the sum of the two individual stimuli Interference – the superposition of two or more waves, amplitudes sum together – “out of phase” or phases shifted by 180 degrees then they will “destructively” interfere – “in phase” or phases not shifted then they will “constructively” interfere

Interference Destructive Constructive PhET website

Interference http://www.rp-photonics.com/img/interference2_s.png

Standing Waves Standing waves – waves that constructively interfere in cavity and “stand” in one spot http://kottan-labs.bgsu.edu/teaching/workshop2001/chapter7_files/image023.gif Node Antinode

Example Question 1 PhET website

Example Question 2 A string of 0.25 kg/m is stretched to a tension of 4 N between 2 plates that are 0.5 m apart. What is the wavelength of the first harmonic in the string? A)4 m B)2 m C)1 m D)0.5 m E)0.25 m

Main Points - Waves Mechanical Wave – a propagating oscillation that moves through a medium Superposition – wave amplitudes add together Interference – when two or more waves superimpose (destructive -> less A and constructive -> bigger A) Standing waves – waves that constructively interfere within a cavity and appear to “stand” in one spot

Download ppt "PHYS16 – Lecture 34 Waves December 3, 2010 “Interference is much clearer in HD”"

Similar presentations