Name: _______________________
April 29-May 24, 2013
Miss Shea Physics
One leader changes everything
Waves
New York State Physics Setting: Physics Standards
Major Understanding 4.3a An oscillating system produces waves. The nature of the system determines the type
of wave produced.
Major Understanding 4.3b Waves carry energy and information without transferring mass. This energy may be
carried by pulses or periodic waves.
Major Understanding 4.3c The model of a wave incorporates the characteristics of amplitude, wavelength,*
frequency*, period*, wave speed*, and phase.
Major Understanding 4.3d Mechanical waves require a material medium through which to travel.
Major Understanding 4.3e Waves are categorized by the direction in which particles in a medium vibrate about
an equilibrium position relative to the direction of propagation of the wave, such as transverse and
longitudinal waves.
Major Understanding 4.3f Resonance occurs when energy is transferred to a system at its natural frequency.
Major Understanding 4.3i When a wave moves from one medium into another, the wave may refract due to a
change in speed. The angle of refraction (measured with respect to the normal) depends on the angle of
incidence and the properties of the media (indices of refraction).*
Major Understanding 4.3l Diffraction occurs when waves pass by obstacles or through openings. The wavelength
of the incident wave and the size of the obstacle or opening affect how the wave spreads out.
Major Understanding 4.3m When waves of a similar nature meet, the resulting interference may be explained
using the principle of superposition. Standing waves are a special case of interference.
Major Understanding 4.3n When a wave source and an observer are in relative motion, the observed frequency
of the waves traveling between them is shifted (Doppler effect).
1
A few key terms:
 A wave is a transfer of __________________ from one point to another within a medium.
 A ______________ causes a disturbance which then travels through the medium in the
form of a wave.
 A ________________ is a substance, material, or space which carries a wave from one
location to another. Waves must have a medium to travel through.
 A ________________ is a single short disturbance that moves through a medium.
 A ________________ wave is a series of regular, evenly timed, disturbances in a medium.
This is sometimes called a wave train.
Types of waves:
 _____________________________ Waves- The vibrations in the wave are parallel to the
direction the wave travels.
Examples: Sound, Seismic P-waves, Compression Waves
 ____________________________ Waves- A wave in which the vibration is perpendicular to
the direction of the wave travel.
Examples: Electromagnetic Waves; Seismic S-Waves
2
Anatomy of a Wave:
 Parts of a wave:
o Longitudinal:
o Transverse
 ____________________________- The maximum displacement of a particle in the medium
for its equilibrium (rest) position.
o The amplitude is directly related to the amount of energy in the wave
o Large Amplitude=___________ Energy
Small Amplitude=___________ Energy
o Amplitude of a sound wave  determines the volume of the sound
 Large amplitude = ______________________________
 Small amplitude = ______________________________
o Amplitude of a light wave determines the brightness of the light
 large amplitude = _____________________________
 small amplitude = ______________________________
 ______________- The number of cycles or complete vibrations occurring per unit of time
o Symbol: _______________
o Units: ______________________
 1 Hz = 1 cycle per second
o Equation_________________________________
o High Frequency
Low Frequency
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o Example: A ruby-throated hummingbird beats its wings at a rate of about 70
wing beats per second. What is the frequency in Hertz of the sound wave?
o Frequency of a sound wave is the pitch High frequency = ____________________________
 Low Frequency = ___________________________
o Frequency of a light wave is the color
 High frequency = ___________________
 Lowe frequency = ___________________
 _____________________- The time required to complete one single vibration (wave).
o Symbol: _________
o Units: ______________________
o Equation: ___________________
o Example: 10 wave cycles pass a point in 1 second, what is the period of the
wave?
 ___________________________- the distance between two successive wave pulses
o Transverse waves- between two ___________ (high points) or between two
__________ (low points)
o Longitudinal waves- between the points of _____________ (particles close
together) or between points of __________________ (particles farther apart)
o Symbol: __________________
o Units: ____________________________________________
 1 nm = 1x10-9 m
o Example: The wavelength is represented by what letter on the diagram:
o Example: Indicate the intervals that represent one full wavelength:
4
 _______________- All the points on a single periodic wave having the same amplitude
and moving in the same direction are said to be in phase
o In phase points are _____________ wavelengths apart (1, 2, 3 etc).
o Just like there are ___________ in a circle, one complete wave length can be
represented by __________
 One half cycle is __________. Points on a wave that are 180 apart are
____________ apart. These are said to be completely out of phase
o All the points of a wave that are in phase is a ________________ (think ripples in a
pond)
 Represented by circles or lines…. each circle or line is one wave front.
These lines also represent the crests of the wave. The spaces between
the lines are the troughs.
Wave speed- how fast the wave travels through a medium





If the medium is uniform, the speed is ____________________
If the medium changes, the speed ___________
Symbol: _______
Units: __________
Equation: _________________
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 Some fun facts
o The speed of light (c) = _________________________
o The speed of ________________ is faster than ______________ in air
o The ________________ the material, the ________________ the speed
 Example: Ocean waves are observed to travel along the water surface during a
developing storm. A Coast Guard weather station observes that there is a vertical
distance from high point to low point of 4.6 meters and a horizontal distance of 8.6
meters between adjacent crests. The waves splash into the station once every 6.2
seconds. Determine speed of these waves.
Sample Problem
The following diagram shows a segment of a periodic wave in a spring traveling to the right
to point I.
a. What type of wave is represented
in the diagram?
e. Determine the speed of the wave.
b. What is the amplitude of the wave?
f. Name two points on the wave that
are in phase
c. What is the wavelength of the
wave?
g. Immediately after the wave
through point I will point H move
up, down, left or right?
d. If the frequency of the wave is 2.0
hertz, what is the period of the
wave?
6
Practice Problems Set 1:
Due:
1.
A sound wave has a frequency of 262 Hz. What is the time between successive wave
crests?
2.
A sound wave with a frequency of 272 Hz has a wavelength of 1.29 m. What is the
velocity of the sound wave?
3.
A sound wave produced by a clock chime 515 m away is heard 1.50 s later.
4.
a.
What is the speed of sound in air?
b.
The sound wave has a frequency of 436 Hz. What is its period?
c.
What is its wavelength?
A hiker shouts toward a vertical cliff 685 m away. The echo is heard 4.00 s later.
a.
What is the speed of sound in air?
b.
The wavelength of the sound is 0.750 m. What is its frequency?
c.
What is the period of the wave?
7
5.
A radio wave, a form of electromagnetic wave, has a frequency of 99.5 MHz (99.5 x
106 Hz). What is its wavelength?
6.
A typical light wave has a wavelength of 580 nm.
a.
What is the wavelength of the light in meters?
b.
What is the frequency of the wave?
7.
The maximum displacement of a particle from its rest position due to wave motion
is called ________________________.
8.
On the wave train shown below, which point is in phase with point A?
What point is completely out of phase with point B?
9.
Compared to the observations made when both the source and the observer are
stationary, when the source of a periodic wave is receding from an observer, there is
an apparent increase in the wave’s _________________________.
8
10.
What physical characteristic of a wave would you change to increase the loudness of
a sound? What characteristic would you change to change the pitch?
Base your answers to questions 11 through 15 on the diagram below which represents a
wave traveling to the right along a horizontal material medium.
11.
If the crest at b takes 2.0 seconds to move from b to f, what is the speed of the wave?
12.
If the period of the wave is 2.0 s, what is its frequency?
13.
What is the wave’s amplitude?
14.
As the wave moves to the right from its present position, in which direction will the
medium at point e first move?
15. What point is in phase with point C?
9
Boundary Behavior- The motion of a wave will change when it reaches the end
of one medium and counters another.
1. _____________________________________- The new medium is immovable.
a. The entire wave is ____________________.
i. If the end is fixed, the reflected wave is inverted
ii. If the end is free, the reflected wave is upright
2. The material goes from _______________________________________________
a. Some of the energy is reflected and returns. This has the same
speed and wavelength as the incident pulse.
b. Some of the energy is transmitted. This has a smaller wavelength
and has a smaller speed than the incident pulse.
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3. The material goes from ______________________________________________
a. Some of the energy will be transmitted. This pulse will have a
larger speed and larger wavelength than the incident pulse.
b. Some of the energy will be reflected. This pulse will have the same
speed and wavelength as the incident pulse.
Example: A pulse is sent along a spring. The spring is attached to a light
thread that is tied to the wall, as shown below.
a.
What happens when the pulse reaches point A?
b.
Is the pulse reflected from A erect or inverted?
c.
What happens when the transmitted pulse reaches B?
d.
Is the pulse reflected from B erect or inverted?
11
THE PERIODIC WAVE PHENOMENA:
Interference- the effect produced by two or more waves which pass
simultaneously through the same region.
 _______________________waves respond to different conditions in __________________ ways
 __________________________- the resulting amplitude at any point is the algebraic sum of the
displacements of the two individual waves.
 _____________________________________- when waves are in phase and therefore
reinforce each other
 ____________________________________- when waves are out of phase and cancel
each other out (either completely or partially).
 _________________________ constructive and destructive interference- occurs
when the waves have the same amplitude and frequency
o antinodes are points of maximum constructive interference
o nodes points of maximum destructive interference
 _______________(the rising and falling of music) are produced by the
interference of two notes of difference frequencies when heard at the
same time.
 Example: Fill in the chart
Displacement of Pulse 1
+1
-1
+1
+1
Displacement of Pulse 2
+1
-1
-1
-2
=
=
=
=
=
Resulting Displacement
Example: Several positions along the medium are labeled with a letter. Categorize
each labeled position along the medium as being a position where either
constructive or destructive interference occurs.
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Diffraction- the spreading of a wave into a region of space behind an obstacle
 If a wave reaches a barrier with a very small opening, the wave will spread out
behind the barrier in a pattern of _______________waves.
Single Slit Diffraction- if a wave is passed through a small hole or
narrow slit, a pattern of light and dark or high and low intensity
regions appears on the screen behind it.
 Due to the interference between the light waves from different parts of
the wave passing through the opening.
 The amount of spreading is related to________________
Double Slit Diffraction- when two sources generate waves in the same
medium they form a predictable interference pattern
 Constructive interference- occurs when the two waves are in ____________
(crest meets crest).
 Occurs at points where the path lengths to each source differs by
an ________________ number of half-wavelengths
 Form ______________________ and ____________________________________
 Destructive interference-occurs when the two waves are out of ____________
(crest meets through)
 occurs at points where the path length to each source differs by an
_______________ number of half-wavelengths
 forms _______________ and ___________________________________
13
Practice Problem Set 2:
Due:
1. When two waves pass each other in a medium, maximum constructive interference
will occur in places where the phase difference between the two waves is
_____________.
2. As a periodic wave passes into a different medium in which the speed of the wave
decreases, the frequency of the wave __________________.
3. A rope vibrates with the two waves shown below. Sketch the resulting wave.
4. The following diagram shows four waves that pass simultaneously through a region.
Which two waves will produce maximum constructive interference if they are
combined?
5. Which pair of waves will produce a resultant wave with the smallest amplitude?
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6. The following diagram represents two waves traveling simultaneously in the same
medium. At which of the following points will maximum constructive interference
occur?
7. A wave spreads into a region behind a barrier. What is the phenomenon called?
8. Which diagram best illustrates the diffraction of waves incident on a barrier?
9. The diagram that follows represent straight wave fronts approaching a narrow
opening in a barrier.
Which diagram best represents the shape of the waves after passing through the
opening?
10. Two wave sources operating in phase in the same medium produce the circular
wave patterns shown in the diagram that follows. The solid lines represent the
wave crests and the dashed lines represent the wave troughs. Which point is at a
position of maximum descriptive interference?
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Standing waves- occur when two waves with the same frequency and
amplitude travel in opposite directions in the same medium.
 Produced when the wave is __________________ by a _______________ boundary.
o Areas of maximum movement are ________________________
o areas of minimum movement are _________________
o In music, harmonics are formed by standing waves and are based on the
number of nodes present
Harmonic
# of Nodes
# of Antinodes
Pattern
n+1
n
--
1st
2nd
3rd
4th
5th
6th
nth
o Example: The string at the right is 5.0 meters long
is vibrating as the fourth harmonic. The string
vibrates up and down with 48 complete vibrational
cycles in 20 seconds. Determine the frequency,
period, wavelength and speed for this wave.
16
and
Resonance- the natural frequency at which an object vibrates
 Every elastic object as a ______________________ at which it will vibrate if disturbed
 If the elastic object receives a series of pulses at this frequency, the object will
vibrate at this frequency with increasing _______________________ (and therefore energy)
 Video Examples
1. Why did the glass break?
2. Why did the bridge collapse?
Doppler Effect- The variation in observed frequency between the source and
observer when one is in relative motion
 When the objects are _________________ each other
the frequency appears to _________________
 When the objects are ________________ the
frequency appears to __________________
 This happens because the ______________ are
moving either closer together or further apart
depending on the motion of the source and the
position of the observer
 Uses of the Doppler effect:
o Red-blue shifts of stars
o Radar
o Sonar
 Explain why the pitch of the ball changed when you threw it to a partner and then
the partner threw it to you.
 Example: If you hear a train whistle pitch drop as the train passes you, can you tell
from which direction the train was coming? Explain.
17
Practice Problems Set 3:
Due:
1. Standing waves are produced by two waves traveling in opposite directions in the
same medium. The two waves must have
a. the same amplitude and the same frequency
b. the same amplitude and different frequencies
c. different amplitudes and the same frequency
d. different amplitudes and different frequencies
2. When the stretched spring of the apparatus represented in the following diagram is
made to vibrate, point P does not move. The location of point P is known as a(n)
___________________________________.
Base your answers to questions 3 and 4 on the following diagram, which shows a standing
wave in a rope.
3. How many nodes are represented?
4. If the rope is 6.0 meters long, what is the wavelength of the standing wave?
5. Two waves traveling in the same medium interfere to produce a standing wave.
What is the phase difference in degrees between the two waves at a node?
6. An opera singer’s voice is able to break a thin crystal glass if a note sung and the
glass have the same natural _____________________________.
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7. When an opera singer hits a high-pitch note, a glass on the opposite die of the opera
hall shatters. What wave phenomena explain this occurrence?
8. What term describes the variations in the observed frequency of a sound wave
when there is relative motion between the source and the receiver?
9. The vibrating tuning for shown in the diagram that follows produces a constant
frequency. The tuning for is being move to the right at a constant speed and
observers are located at points A, B, C, and D. Which observes hears the lowest
frequency? Justify your response.
10. The driver of a car hears the siren of an ambulance that is moving away from here.
If the actual frequency of the siren is 2000 hertz, the frequency heard by the driver
may be (a) 1900 Hz (b) 2000 Hz (c) 2100 Hz (d) 4000 Hz. Justify your response.
11. The light from a distance star displays a Doppler red shift. What does this mean
about the motion of the star relative to the Earth?
19
The Special Nature of Light
 So far we have described light as a wave (in the next unit we will re-examine this
definition of light)
o It displays the following wave characteristics:
1. _______________________________
2. _______________________________
3. _______________________________
o Light also displays other special wave-like characteristics:
1. _______________________________
2. _______________________________
3. _______________________________
Light waves are part of the _______________________________________________ (EM spectrum)
o these waves consist of periodically changing _________________________________
fields that move through a vacuum
o All these waves are given off by the__________________
o The speed of all electromagnetic wave is ____________________
 Symbol: ____________
o All EM waves are produced by _____________________________________________
o The EM spectrum is a complete range of frequencies and wavelengths.
 A chart of the EM spectrum is in the reference table
 Uses of the EM spectrum
o _____________________________- is a small portion of the spectrum (1%)
 All colors we see are the reflection of a visible light wave
frequency
o _____________________________- used in radar systems, long distance phone
communications, and to cook foods
 longest wave lengths and smallest frequency
o _____________________________- appears as heat of an object
 used in heat lamps and infrared photograph
o ____________________________- the part of the wave spectrum from the sun that
causes sunburns
 high frequency and small wavelength
 the ozone of earth partly filters out these waves
o ___________________________- used by medical professionals as a diagnostic
tool
o ____________________________- emitted by radioactive nuclei
 harmful to living tissues
 highest frequency and smallest wavelength
20
Practice Problems Set 4:
Due:
1. Convert 700 nm, the wavelength of red light, to meters.
2. Light takes 1.28 s to travel from the moon to Earth. What is the distance between
them?
3. The sun is 1.5 x 108 km from Earth. How long does it take for its light to reach us?
4. Radio stations are usually identified by their frequency. One radio station in the
middle of the FM band has a frequency of 99.0 MHz. What is its wavelength?
5. What is the frequency of a light wave having a wavelength of 5.00x10-7 meter in a
vacuum?
Ray Diagrams- represent the path a wave takes as it interacts with various
conditions
 Parts of a ray diagram:
 _________________- a straight line indication the direction of wave travel
 ________________ ray- originates in one medium and reaches the surface of a second
 ________________ ray- rebounds off the surface of a second medium
 ________________ ray- bends when enteracts the second medium
 _________________________- a line drawn perpendicular to a surface
 Angle of ______________ (i)- the angle between the normal line and the incident ray
 Angle of _____________ (r)- the angle between the normal line and the reflected ray
21
Reflection- the bouncing back of waves when it reaches a second medium
 Types of reflection
1. _____________________Reflection- produced by _________________________________ surfaces
a. all incident rays are parallel
b. all normal lines are parallel
c. all reflected rays are parallel
d. produces a mirror image
e. Examples: mirrors, still bodies of water, windows at night
2. _____________ Reflection- produced by the _________________ of light caused by rough,
irregular surfaces
a. all incident rays are parallel
b. all normal are not parallel
c. all reflected rays are not parallel
d. prevents image formation
e. Examples: paper, blue sky, ground, tinfoil
 _____________________________- the angle of incident equals the angle of reflection (i=r)
 The incident ray, normal line, and reflected ray are in one plane
 Reflected images in a plane mirror are virtual (appear beyond the surface). The
diagram below shows the ray diagram of an image that appears when you look into
a plane mirror.
22
Practice Problems Set 5:
Due:
1. A ray of light is reflected from a plane mirror. If the angle between the incident and
reflected rays is 40., what is the angle of incidence?
2. When a ray of light strikes a plane mirror perpendicular to its surface, what is the
angle of reflection?
3. A beam of light from Earth is reflected by an object in space. If the round trip takes
2.0s, what is the object’s distance from Earth?
4. The following diagram shows parallel rays of light interacting with a barrier. Which
phenomenon of light is illustrated? ___________________________
5. Which diagram best represents the reflection of objects O in plane mirror M?
6. A ray is reflected from a surface, as shown in the diagram that follows. Which letter
represents the angle of incidence? ________ Which letter represents the angle of
reflection? _________
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7. A tall person is standing in front of a vertical plane mirror 2.0 meters high as shown
in the following diagram. A ray of light reflections off the mirror, allowing him to
see his food. Approximately how far up the mirror from the floor does this ray
strike the mirror. Hint: Draw the ray diagram that shows the reflected ray hitting
his eye to help you determine this.
8. The following diagram represents a light ray being reflected from a lane mirror. The
angle between the incident ray and the reflected ray is 70. What is the angle of
incident for this ray?
9. When a ray strikes a mirror perpendicular to its surface, what is the angle of
reflection?
10. Which diagram best represents wave reflection?
24
Refraction- the change in direction (bending) of a wave as the wave travels
from one medium into another
 Occurs when:
 _________________________________________ (not 0)
AND
 The __________________________________changes as it passes into the new medium
 The light will follow the path of _____________________________ (highest speed)
Four cases:
1. The conditions: Medium 1 is less dense than medium 2
a. v1>v2 so light slows down in the second medium
b. the ray bends toward the normal line (1>2)
2. The conditions: Medium 1 is more dense than medium 2
a. v1<v2 so light speeds up in the second medium
b. the ray bends away from the normal line (1<2)
3. The conditions: Medium 1 is the same density as medium 2
a. v1=v2 so light doesn’t change speed
b. the ray does not bend, there is no refraction, and 1=2
4. The conditions: Light enters medium 2 at 0
a. The ray does not bend and there is no refraction
b. 1=2=0
 Explain the following demonstrations:
1. Why does the pencil appear to bend when placed in the glass of water?
2. Why does the Pyrex beaker disappear?
3. Why can’t you grab the penny out of the bowl?
25
Index of Refraction- The ratio of the speed of light in a vacuum
(air/space) to the speed of light in a medium
 Symbol: ___________________
 absolute indicies of refraction are listed in the reference table
 Equation:__________ =
 Example: What is the index of refraction of a medium where light travels at
1.95x108 meters per second?
 Example: What is the speed of light in diamond?
 At the boundary between two different mediums the ________________ of a wave
stays ______________ so we can calculate the ______________________ or ______________
of the wave in the new medium.
 Equation:
=
=
 Note 1 is the incident medium and 2 is the refractive medium
Snell’s Law- the ratio of the absolute indicies of refraction is inversely
proportional to the sine of the angles
 Equation: __________________________________________
26
Practice: The diagram representing a ray of monochromatic light, having a frequency of
5.09x1014 hertz, as it is about to emerge from liquid glycerol into air. The index of
refraction of glycerol, n1, is 1.47. The index of refraction of air, n2, is 1.
Air
Glycerol
a. On the diagram label of the angle of incidence, 1. Determine the measure to
the nearest degree.
b. Determine the corresponding angle of refraction to the nearest degree.
c. On the diagram, draw the refracted ray, label the angle of refraction 2, and
indicates its measurement to the nearest degree.
d. Determine the speed of light in glycerol.
e. Determine the wavelength of the ling in air in nanometers with the proper
number of significant digits.
f. What is the ratio of the speed of light in glycerol to the speed of light in air?
27
Practice Problems Set 6:
Due:
1. The absolute index of refraction for a medium is 1.6. How fast will light travel in the
medium?
2. The index of refraction of water is 1.33. Calculate the speed of light in water.
3. The speed of light in a plastic is 2.00 x 108 m/s. What is the index of refraction of the
plastic?
4. A ray of light traveling through air is incident upon a sheet of crown glass at an
angle of 30.0. What is the angle of refraction?
5. Light in air is incident upon a piece of crown glass at an angle of 45.0. What is the
angle of refraction?
6. A ray of light passes from air into water at an angle of 30.0. Find the angle of
refraction.
7. A ray of light is incident on the surface of a block of flint glass at an angle of 40..
Part of the light is reflected and part is refracted. Find the angle between the
reflected and refracted rays.
28
8. A light ray incident upon an interface of water and an unknown transmitting
substance, X, is refracted as shown in the diagram below. Find the speed of light in
medium X.
9. As a wave enters a new medium, there may be a change in the wave’s
a. frequency
c. period
b. speed
d. phase
10. Which arrow best represents the path that a monochromatic ray of light travels as it
passes through air, corn oil, glycerol and back into air?
11. A beam of monochromatic red light passes obliquely from air into water. Which
characteristic of the light does not change:
a. direction
b. velocity
c. frequency d. wavelength
12. The frequency of a ray of light is 5.09x1014 Hz. What is the ratio of the speed of this
ray in diamond to its speed in zircon?
13. A ray of light is incident on a block of Lucite at an angel of 60 from the normal. The
angle of refraction of this ray in Lucite is closest to what degree?
29
14. The figure below depicts a ray of light about to emerge in air from water.
a. On the diagram, indicate the angle of incidence by 1 and label its measure to
the nearest degree.
b. Calculate the corresponding angle of refraction to the nearest degree.
c. On the diagram, draw the refracted light ray, label the angle of refraction 2,
and indicate its measure to the nearest degree.
d. At a boundary between two media, some of the incident light is always
reflected. On the diagram, draw the reflected ray, label the angle of reflection
3, and indicate its measure to the nearest degree.
e. If the angle of incidence is gradually changed from its present value to 55,
what changes if any would occur in the reflected and refracted rays?
30
15. A ray of monochromatic light, having a frequency of 5.09x1014 hertz, is traveling in
air. The ray is incident on the surface of a block of flint glass at an angle of 40, as
shown. Part of the light is reflected at the air-glass interface and part is refracted in
the glass.
a. On the diagram, draw the reflected ray and angle the angle of reflection with
its measure to the nearest degree.
b. Determine the angle of refract in the flint glass to the nearest degree.
c. On the diagram draw the refracted raw. Label it “refracted ray.”
d. Measure the angle between the reflected and the refracted ray and indicate
the value in the appropriate place on the diagram.
e. Determine the wavelength of the light ray in the flint glass.
31
Dispersion- the separation of polychromatic light into its component
wavelengths
 Polychromatic light
o Contains waves of various frequencies
 has different colors of light
o Each frequency has a ____________________ index of refraction
 Red: __________________ frequency, bends the _______________
 Violet: __________________ frequency, bends the ________________
 _________________________________- a substance in which the speed of the wave
depends on the wave’s frequency
o Examples:
 Prisms
 Water droplets
 Diamonds
 Motor oil
 Bubbles
 CDs, DVDS
 Plastic films
 _______________________________- substance in which the speed of the wave does not
depend on the wave’s frequency.
o Examples:
 A vacuum to light or electromagnetic waves
 Air to sound waves
Polarization- the process of producing light so that all vibrations occur in one
plane
 Vibrations that cause light occur in ________________ planes: horizontal, vertical, etc
 Only ___________________ waves can be polarized
o _________________ waves are already propagating in one direction
 A _____________________________ will cancel out one plane of vibration causing
polarized light to get through.
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o Surfaces such as _____________________________ can polarize light as well-when
the light is reflected off the surface, it is vibrating in just one direction.
 This is why polarized sunglasses were invented
 This is causing problems for many bugs- they confused the polarized
light from blacktops as polarized light from water and try to inhabit
unsafe places
 Everyday uses:
o _______________________________
o _______________________________
 Explain the following demos:
1. Why did you see the rainbow of lights?
2. Why did the screen change from one color to the next?
3. Why did the cell phone screen go black?
4. How can you tell if sunglasses are really polarized?
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Practice Problem Set 7:
Due:
1. The indices of refraction for diamond are 2.41 for red light and 2.45 for blue light.
Suppose white light is incident on the diamond at 30.0. Find the angles of
refraction for these two colors.
2. The indices of refraction for crown glass are 1.51 for red light and 1.53 for blue light.
White light is incident on the glass at 30.0.
a. Find the angles of refraction for these two colors.
b. Compare the difference in angles to those for diamond in problem #1.
3. The indices of refraction for crown glass are 1.53 for violet light and 1.51 for red
light.
a. What is the speed of violet light in crown glass?
b. What is the speed of red light in crown glass?
4. Carson Busses is driving down the road on a sunny day. Reflection of light off the
road surface results in a large amount of polarization and subsequent glare.
Annoyed by the glare, Carson pulls out is Polaroid sunglasses. How must the axes of
polarization be oriented in order to block the glare?
5. Describe the result of shining light through the two polarizing filters whose
transmission axes are parallel to each other. Describe the intensity and orientation
of the emerging light. What happens to the intensity and orientation of the
emerging light if the two polarizing filters were perpendicular to each other?
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