Download Block 3: Physics of Waves Chapter 12: Sound Skill Goals: • Describe

Block 3: Physics of Waves
Chapter 12: Sound
Skill Goals:
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Describe production of sounds
Measure the speed of sound
Relate pitch and loudness to frequency and amplitude
Describe how sound travels
Sound is a longitudinal (compression)
wave
Sound waves must have a medium to
travel through.
The denser the medium, the faster the
sound wave travels.
Sound waves are composed of
compression (crest) and rarefaction
(trough)
Sound is created by vibrating the
molecules of a medium
String Instruments: stings cause body of
instrument to vibrate and create sound
waves
Wind instruments – tube vibrates a column
of air
Percussion instruments – body of
instrument vibrates.
Measuring the speed of sound
The sound source and sound detector are
separated by a known distance.
The time interval is measured
electronically.
Speed is calculated s = d/t
Frequency and pitch are related
f = 1/T (inverse of period)
units are Hertz (Hz) = cycles per second
high frequency sounds are perceived as
high pitch
Amplitude and loudness are related
The greater the amplitude of a sound
wave, the greater the energy.
Sound intensity is a measure of energy.
Loudness is perceived volume.
High amplitude, louder perceived sound
Human hearing range
20 Hz to 20,000 Hz
Block 3: Physics of Waves
Chapter 13: Light
Skill Goals:
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Describe how a plane mirror forms and image
Construct ray diagrams of reflection using law of reflection.
Describe refraction of light
Calculate refractive index using Snell’s Law
Describe total internal reflection
Use ray diagrams to explain how a lens forms images
Explain how a magnifying glass works
Law of reflection: The angle of
incidence (i) equals the angle
of reflection.
Mirrors form virtual images that
appear equal distance behind
the mirror and are reversed
Light is refracted (bent) when it
moves from one medium to
another.
The index of refraction (n) of
the medium determines the
angle of refraction
Refractive index n
n = speed of light/speed of light in medium
Snell’s Law
n = sin(i)/sin(r)
Ray diagram for refraction
Ray diagram of real image.
Image is real (can project on a
screen)
Image is on opposite side of
lens from the object
Image is inverted
Image may be reduced or
enlarged
Ray diagram of virtual image
(magnifying glass)
Image is virtual (can’t
projected on screen)
be
Image is upright and enlarged
Total internal reflection
The angle of incidence is greater than the critical
angle of the medium
Block 3: Physics of Waves
Chapter 14: Properties of Waves
Skill Goals:
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Describe transverse and longitudinal waves
Explain speed, amplitude, frequency and wavelength
Apply the wave equation
Describe reflection, refraction, and diffraction of waves
Identify parts of a wave
Frequency and period are
related
Period (T) = time for one cycle
Frequency (f) = cycles per second
T = 1/f
The wave equation relates
speed, wavelength and
frequency
Reflection of waves
Frequency, wavelength and
speed do not change
Refraction of waves
Frequency remains the same,
speed and wavelength change.
f = 1/T
v = λf
v = speed m/s
λ = wavelength m
f = frequency Hz
Diffraction – wave spreads out
Block 3: Physics of Waves
Chapter 15: Spectra
Skill Goals:
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Describe dispersion of light by a prism
Describe features of electromagnetic spectrum
Understand all EM waves travel at speed of light
Apply the wave equation to EM waves
A prism will disperse white light.
White light will be dispersed into
different wavelengths by refraction.
Longer wavelengths (red) will be bent
less than shorter wavelengths (violet)
The electromagnetic spectrum relates
wavelength, frequency, and energy
Long λ, low f, low energy (radio waves)
Short λ, high f, high energy (gamma rays)
EM waves travel at the speed of light
and behave according to the wave
equation
Visible light is in the middle of the EM
spectrum
Speed of light c = 3 x 108 m/s
EM Wave equation
c = λf