HNRT 227 Fall 2015 Chapter 6 Wave Motion, Sound and Electromagnetism 17 September 2015 presented by Prof. Geller

Recall from Chapters 1-5 zUnits of length, mass and time, and metric Prefixes zDensity and its units zThe Scientific Method zSpeed, velocity, acceleration zForces zFalling objects, Newton’s Laws of Motion and Gravity zWork, Potential Energy and Kinetic Energy zConservation of Energy, Types/Sources of Energy zKinetic Molecular Theory, Temperature and Heat zPhases of matter and Thermodynamics zElectricity zMagnetism

Forces and Vibrations zVibration yback and forth motion zAmplitude yextent of displacement from the equilibrium position zCycle yone complete vibration zPeriod ytime required to complete one cycle zFrequency ynumber of cycles per second zRelationship between period and frequency yT = 1 / ff = 1 / T

Waves zLongitudinal ydisturbance that causes particles to move closer together or farther apart IN THE SAME DIRECTION the wave is moving zTransverse ydisturbance that causes motion PERPENDICULAR to the direction that the wave is moving zIn general, liquids carry longitudinal waves but not transverse waves yTransverse waves, such as water waves, dissipate all their energy at the phase interface zWe use same terms as vibrations, for waves  v =  * f

Sound Waves zSound does not travel in a vacuum zSound moves through solids faster than any gas zVelocity of sound is effected by composition and temperature of gas

Reflection, Refraction and Interference zReflection ywaves bouncing back off of a boundary zRefraction ychange in direction of wave crossing a boundary zInterference yinteraction of waves xdestructive interference xconstructive interference

Resonance zNatural frequency yfrequency of vibration determined by the object’s composition and shape zResonance ywhen frequency of external force matches natural frequency

Doppler Effect and Sonic Boom zDoppler Effect yApparent change in frequency of a wave caused by the relative motion of the source or observer xpitch of train approaching, departing zSonic boom yshock wave caused by object moving at speed of sound or faster

Electromagnetism zMagnetic Fields ygenerated by electric current zEnergy conversion yelectric motors yelectric generators yspeakers zMaxwell’s Equations ysummary of electromagnetic laws and interactions…

Waves zTypes of waves ylongitudinal xe.g. sound ytransverse xe.g. electromagnetic waves zVelocity, frequency and wavelength ywave velocity = wavelength times frequency xwatch your units

Electromagnetism zElectricity according to Gauss yrelates electricity to electric charge zFaraday’s Law yrelates electric fields to magnetic fields zMagnetism according to Gauss yrelates magnetism to electricity

Maxwell’s Equations zAmpere-Maxwell Law yrelates magnetic field to electricity zMaxwell yunifies electricity and magnetism into electromagnetism

Electromagnetic Interactions zTransmission vs. opacity zAbsorption vs. emission zScattering yrefraction yreflection ydiffraction yinterference

Electromagnetic Spectrum zVisible yRed (~7000 A or 700 nm) yOrange, Yellow, Green, Blue, Indigo yViolet (~4000 A or 400 nm) zMore than meets the eye yradio, microwave, infrared, ROYGBIV (visible), ultraviolet, X-rays, gamma rays xfrom lowest energy to highest energy xfrom longest to shortest wavelength xfrom lowest to highest frequency

Reflection and Refraction (not all in text) zReflection ythe angle of incidence is equal to the angle of reflection   i =  r zVirtual image ylight rays appear to originate from zReal image ylight rays really do meet here zRefraction ychange of direction of light yn = c / v [defines index of refraction]

Diffraction, Interference and Polarization (not all in text) zDiffraction ylight rays appear to bend around the edge of an object zInterference ylight rays interacting with other light rays causing reinforcement or canceling or some combination of the two zPolarization yvibrates/oscillates in a single plane

Doppler Shift zA change in measured frequency caused by the motion of the observer or the source yclassical example of pitch of train coming towards you and moving away ywrt light it is either red-shifted (away) or blue- shifted (towards)