hnrt 227 fall 2015 chapter 6 wave motion, sound and electromagnetism 17 september 2015 presented by...
DESCRIPTION
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 / TTRANSCRIPT
HNRT 227 Fall 2015Chapter 6
Wave Motion, Sound andElectromagnetism17 September 2015presented by Prof. Geller
Recall from Chapters 1-5 Units of length, mass and time, and metric Prefixes Density and its units The Scientific Method Speed, velocity, acceleration Forces Falling objects, Newton’s Laws of Motion and Gravity Work, Potential Energy and Kinetic Energy Conservation of Energy, Types/Sources of Energy Kinetic Molecular Theory, Temperature and Heat Phases of matter and Thermodynamics Electricity Magnetism
Forces and Vibrations Vibration
back and forth motion Amplitude
extent of displacement from the equilibrium position Cycle
one complete vibration Period
time required to complete one cycle Frequency
number of cycles per second Relationship between period and frequency
T = 1 / f f = 1 / T
WavesLongitudinal
disturbance that causes particles to move closer together or farther apart IN THE SAME DIRECTION the wave is moving
Transverse disturbance that causes motion PERPENDICULAR
to the direction that the wave is movingIn general, liquids carry longitudinal waves
but not transverse waves Transverse waves, such as water waves, dissipate
all their energy at the phase interfaceWe use same terms as vibrations, for wavesv =* f
Sound WavesSound does not travel in a vacuumSound moves through solids faster
than any gasVelocity of sound is effected by
composition and temperature of gas
Reflection, Refraction and InterferenceReflection
waves bouncing back off of a boundaryRefraction
change in direction of wave crossing a boundary
Interference interaction of waves
destructive interferenceconstructive interference
ResonanceNatural frequency
frequency of vibration determined by the object’s composition and shape
Resonance when frequency of external force
matches natural frequency
Doppler Effect and Sonic Boom
Doppler Effect Apparent change in frequency of a
wave caused by the relative motion of the source or observerpitch of train approaching, departing
Sonic boom shock wave caused by object
moving at speed of sound or faster
ElectromagnetismMagnetic Fields
generated by electric currentEnergy conversion
electric motors electric generators speakers
Maxwell’s Equations summary of electromagnetic laws and
interactions…
WavesTypes of waves
longitudinale.g. sound
transversee.g. electromagnetic waves
Velocity, frequency and wavelength wave velocity = wavelength times
frequencywatch your units
ElectromagnetismElectricity according
to Gauss relates electricity to
electric chargeFaraday’s Law
relates electric fields to magnetic fields
Magnetism according to Gauss relates magnetism to
electricity
Maxwell’s EquationsAmpere-Maxwell Law
relates magnetic field to electricity
Maxwell unifies electricity and
magnetism into electromagnetism
Electromagnetic InteractionsTransmission vs. opacityAbsorption vs. emissionScattering
refraction reflection diffraction interference
Electromagnetic Spectrum Visible
Red (~7000 A or 700 nm) Orange, Yellow, Green,
Blue, Indigo Violet (~4000 A or 400 nm)
More than meets the eye radio, microwave, infrared,
ROYGBIV (visible), ultraviolet, X-rays, gamma rays
from lowest energy to highest energy
from longest to shortest wavelength
from lowest to highest frequency
Reflection and Refraction (not all in text)Reflection
the angle of incidence is equal to the angle of reflection
i = r
Virtual image light rays appear to originate from
Real image light rays really do meet here
Refraction change of direction of light n = c / v [defines index of refraction]
Diffraction, Interference and Polarization (not all in text)Diffraction
light rays appear to bend around the edge of an object
Interference light rays interacting with other light
rays causing reinforcement or canceling or some combination of the two
Polarization vibrates/oscillates in a single plane
Doppler ShiftA change in measured frequency caused by
the motion of the observer or the source classical example of pitch of train coming towards
you and moving away wrt light it is either red-shifted (away) or blue-
shifted (towards)