AIM:
What is a wave and how do we measure and
describe them?
Do Now:
Draw a wave and label any part of the wave
you know.
Homework
Make a poster of the 4 different types of
waves
Simple Harmonic Oscillators
Mass on a spring
• An object in simple harmonic motion experiences a
restoring force that continuously pulls the object
back towards its equilibrium positon.
• The oscillator vibrates about an equilibrium
position (or mean position) between two extreme
positions of maximum displacement in a periodic
manner
– Periodic means regular (same every time) and repeating
Which of the following waves
is Periodic? Justify.
A
B
Parameters
and parts
of waves
• Period (T):
Vocabulary
– The time for one oscillation
– Measured in Seconds
– Period = Time/number of oscillations
T
• Frequency (f)
– The number of oscillations in one second
– Measured in Hertz; Hz (1/s or s-1)
– Frequency = Number of oscillations/time
f
• Mathematical Relationship between Period and Frequency
– Period and frequency are inversely related
1
T
f
1
f 
T
Tf  1
Examples
1. A mass on a spring completes 10 oscillations in 30
seconds.
a. What is the period of oscillation? 3 seconds
b. What is the frequency of oscillation? 0.33 Hertz
2. A pendulum completes 5 swings in a minute
a. What is the frequency of oscillation? 0.083 Hertz
b. What is the period of oscillation? 12 seconds
Waves
• Waves are repetitive disturbances that transfer ENERGY
without transferring MATTER
– energy transferred without matter being transferred
• Mechanical Waves require a medium to travel through.
• Mediums include; water, air, anything solid, liquid, or gas
• SOUND is a mechanical wave
• "the wave"
• Electromagnetic Waves do not require a medium to
travel through. They can travel through a vacuum
(empty space)
• Empty space exists outside of Earth’s atmosphere
• LIGHT, Xrays, Radio Waves… are all examples of electromagnetic
waves
• electromagnetic waves
Write out the full sentences and fill
in the blank
1. A(n) ____________ wave can travel through a
vacuum
2. ___________ is the number of waves that pass by
per time.
3. A _________ is a substance a wave can travel
through.
4. The amount of time it takes for one complete cycle
of a wave is called the _____________.
5. A(n) __________ wave requires a medium to travel
through.
Two Classes of Waves
Transverse Waves
The particles vibrate in
a direction that is
perpendicular to the
waves propagation
(direction of travel)
Longitudinal Waves
The particles vibrate in
a direction that is
parallel to the waves
propagation
Wave Pulse
One single Vibration or disturbance
• Transverse Pulse
• Longitudinal Pulse
One Crest
Or
One Trough
One rarefaction
Or
One compression
Parts of a Periodic Wave
Crest: the top-most part of a wave
Wavelength (λ): the distance
Amplitude:
the
distance
from
the
between two similar points on a
equilibrium
line
to
the
crest
or
to
wave (measured in meters)
the trough (measure in meters)
Trough: the bottom-most part of a wave
This is a ________________
wave which means that the
particles vibrate ____________
to the direction the wave is
moving.
On the wave above, label
- One crest
- One trough
- One wavelength
- One amplitude
This is a __________________
wave which means that the
particles vibrate ____________
to the direction the wave is
moving.
On the above wave, label
- The compression
- The rarefaction
- One wavelength
Sound Waves vs. Light Waves
Sound Waves
Light Waves
• Mechanical Wave
• Longitudinal wave
• Amplitude tells you about
volume
• Frequency tells you about pitch
• The speed of sound in air is
about 330m/s
• Sound travels faster in most
solids than it does in air
• Electromagnetic wave
• Transverse wave
• Amplitude tells you about
intensity
• Frequency tells you about type
of wave/color
• The speed of light in air is
3x108m/s
• Light slows down in solids
Phase
• The relative position between…
– Two different points on the same wave
• Phase is measured in degrees and follows the
conventions of a sine curve.
90o
One-quarter wavelength
180o
Half wavelength
Reference
Point
0o
360o
One full wavelength
270o
three-quarter wavelength
Phase
The relative position between two separate waves
IN PHASE (360o)
– means the waves are in the
exact same positons (carbon
copies of each other)
180o out of phase
• Means they are opposite each
other (1/2 a wave behind)
standing wave
• A wave that appears to be “standing still” and not moving either
left or right.
- Particles vibrate up and down
• In order to create a standing wave, you need
- Two waves, moving in opposite directions, with the same
amplitude and frequency
Antinodes:
Nodes: points
points that
that move
don’t the
move
most
Standing Wave Diagrams
Fundamental Frequency (1st Harmonic)
λ=2L
2nd Harmonic
λ=L
3rd Harmonic
1.5λ=L
λ=2/3L
4th Harmonic
λ=1/2L
Measuring Parameters
of a Wave
• Goal: we are going to use a standing wave to measure and
investigate the affect of the amplitude, frequency, period,
and wavelength on the speed of a transverse wave.
• Prediction: Which of the four parameters do you think can
be used to determine the speed of the wave and why.
• Background: in a paragraph, please define all bolded
words above.
• Diagram: Draw a diagram of a transverse wave and label all
the parts of the wave.
• Materials
– Slinky, stopwatch, meter stick
Procedure
• Using a slinky, we will create a standing wave between
two people standing 4 meters apart.
• Once person will establish a frequency that will
produce a standing wave vibrating at its fundamental
frequency with an amplitude of 0.5 meters
• Once the wave is established, the timers will time how
long it takes for20 oscillations. Record the values in the
table
• This will be repeated for an amplitude of 1m.
• The frequency will then be changed to produce a
standing wave in the 2nd harmonic and steps 3-4 will be
repeated.
• Create a wave in the 3rd harmonic and repeat steps 3-4
• Create a wave in the 4th harmonic and repeat steps 3-4
• Data
Amplitude of 0.5m
wavelength
(m)
Time
for 20
(s)
Period
(s)
Frequency Speed
(Hz)
(m/s)
Amplitude of 1.0m
wavelength
(m)
Time
for 20
(s)
Period
(s)
Frequency Speed
(Hz)
(m/s)
• Analysis
– Show a sample calculation for each of the following
• Period of the wave
• Frequency of the wave
• Speed of the wave.
– What formula did you come up with to calculate this? (hint: use the units!)
• Percent difference between velocities.
– Do they appear different?
• Conclusion
– Restate goal
– What is the formula for the speed of the wave?
– What parameters affect the speed, which don’t?
• If the frequency was changed, did the speed or the wavelength
change?
– How could you change the speed of this wave?
– Sources of error/one future experiment
Wave Propagation
and ECHOs
Wave Propagation
When given distance
𝒅
𝒗=
𝒕
1. A wave moving at 4m/s travels 20m through
the air. How long does it take?
5 seconds
2. How long does it take light to travel from the
Earth to the moon?
1.28 seconds
Wave
Propagation
When given wavelength or
frequency
𝑣 = 𝑓λ
3. Red light has a frequency of 4x1014 Hz. What is its
wavelength?
7.5x10-7 m
4. A light wave has a wavelength of 480nm, what color is it?
BLUE
Reflection of sound
• The bouncing of a wave off of a surface.
• ECHOs
If the speed of sound in
water is 1500m/s and
the signal takes 0.8
seconds to come back to
the boat, HOW DEEP IS
THE WATER?
600m
Echos
A person in the grand canyon (at STP) screams
and hears the sound come back to her 1.2
seconds later. How far away is the other face of
the canyon?
199m
HOMEWORK
CHECKED TOMORROW
Pg 153-155
#26-47
AIM:
What is Reflection?
Do Now:
Find your partner and create your answer sheet
to hand in for numbers 26-47 in the blue book
Homework
Castle Learning Assignment due FRIDAY!
Recall…
• You are standing on a dock and observe 15 waves
pass you in 1 minute.
– What is the frequency of the waves? 0.25 Hz
– What is the period of the wave? 4 seconds
• What is the difference between a mechanical and
Mechanical waves need a medium to
electromagnetic wave? travel
through, electromagnetic waves can
travel through a vacuum
• What is the difference between a transverse and
A transverse wave has particles vibrating
longitudinal wave? perpendicular to the direction of propagation,
longitudinal waves have particles that vibrate
parallel to the direction of propagation.
The Electromagnetic Spectrum
• ALL electromagnetic waves travel at the speed of
light!
– c is the symbol for the constant “speed of light”
– c is always equal to 3x108 m/s when electromagnetic
waves are traveling through a vacuum.
• This speed can be decreased by sending light through a
different medium
• Nothing can ever travel faster than the speed of light.
• Visible light is the same type of wave as a radio wave, an Xray,
or a microwave. Its just a different size!
• electromagnetic spectrum
The Electromagnetic Spectrum
VERY
wavelengths
VERYhigh
small
wavelengths
VERY
VERYhigh
low frequencies
frequencies
Visible Spectrum.
Each color is within
these FREQUENCY
ranges. Remember,
higher frequency,
lower wavelength
The Electromagnetic Spectrum
meters
Nanometers
Kilometers
Megahertz
Gigahertz
The Electromagnetic Spectrum
• A wave has a frequency of 5.1x1014 Hz.
– What color is it? yellow
– What is the order of magnitude of its wavelength?
10-7 m
• A wave has a wavelength of 10nm.
– What 2 types of electromagnetic radiation could it
be? X-rays or ultraviolet
– What would be the order of magnitude of its
frequency? 1017 Hz or 1018 Hz
Calculating the speed of a wave
1. A 5m long wave passes the end of a dock once
every 10 seconds.
a. What is the period of the wave?
b. What is the speed of the wave?
10 seconds
0.5m/s
2. A light wave has a frequency of 6MHz
a.
b.
c.
d.
6x106 Hz
What is the frequency in Hertz?
What is the speed of the wave? 3x108 m/s
What is the wavelength of the light? 50m
What type of light wave is this? Radio Waves
Wave
Behaviors
3 Options
• When a wave hits a
boundary, it does a
combination of 3 things
– Reflection
• Bounces off the boundary
– Absorption
• Gets absorbed and turned
into heat
– Transmission
• Goes through the
boundary
Two types of wave sources
Point Source
• One point that oscillates
– Like a child bobbing in the
pool.
– Produce circular waves
Plane Source
• An extended (rectangular)
source that oscillates.
– Produce plane waves
Wave Front Diagrams
• Side View
• Top View
Diffraction
• Diffraction is the bending of
a wave around a barrier
– Consider a door cracked
open, what shape does the
light make?
• If it didn’t bend, it would be a
straight column
• As you can see the light ‘fans
out’ after it passes through the
barrier
What does the Amount of
Diffraction Depend on?
Small amount of Diffraction
• Small wavelength
• Large opening
Large amount of Diffraction
• Large wavelength
• Small opening
Other common Diffraction Patterns
Corner
Island
Constructive Interference
- When a crest meets a crest
- When a trough meets a trough
- Full wavelength path difference
+
=
+
=
Destructive Interference
- When a crest meets a trough
- Half wavelength path difference
=
+
• Double slit
Aim: How do we recognize various wave behaviors?
DO NOW:
1. Which wave phenomena is
exemplified by this picture?
2. As the wave propagates, explain
what happens to the…
-speed of the wave
-the wavelength of the wave
-the frequency of the wave
- the amplitude of the wave
HW: Castle Learning on Diffraction-Due
tomorrow. Counts as a 10pt HW assignment
Law of Reflection
How to draw the diagram
• The Law of Reflection states
– Angle of incidence is equalNormal
to the angle
of reflection
Line:
A
Angle of incidence ϴi:
angle made between the incident
Incidence
The light
ray andRay:
the normal
lineray on the way
INTO the surface
reference line always
Angleperpendicular
of Reflectiontoϴr:
drawn
angle
made between
the light
reflected
Reflected
Ray: The
ray on
the
surface
USE
A
ray
normal
linethe surface
the and
way the
AWAY
FROM
PROTRACTOR!!!!
ϴi ϴr
Reflection of Light
• The bouncing of a wave off of a surface .
– Regular reflection
• Bouncing off of a Smooth surface
– Mirrors, ponds
– You can see an image of the object
– Diffuse Reflection
• Bouncing off of a Rough surface
– The road, leaves, furniture, cloths
– You can see light, but no image
Reflection Ray Diagram
Object Distance
Image Distance
Object
Eye sees
two
diverging
Normal Line
rays and
traces them
back
Image
Appears
where the
virtual
rays cross
Incident
Angle
Reflected
Angle
Mirror
Law of Reflection in a
PLANE mirror:
-Object distance (do) is
equal to image
distance (di)
Reflection Lab
Goals:
1. To draw a 2-ray diagram of a single pin image
a. Use this diagram to compare the incident angles to the
reflected angle
-
Use percent difference to determine if the object distance is
the same as the image distance
b. Use this diagram to compare image distance to object
distance
-
Use percent difference to determine if the object distance is
the same as the image distance
1. Draw a line down the middle of the page,
perpendicular to the edge of the page
2. Prop the mirror up against the book with the BACK
surface of the mirror on your mirror line. Make sure
the cardboard is under the paper
3. Stick the pin in the middle of the
page
4. Look in the mirror from the angle and
locate the image of the pin in the mirror
Image of
the pin
5. Line up the edge of the ruler such that if extended into the
mirror, it would run straight into the pin. Trace that line
6. Repeat step 5 from the other side
7. Extend the reflected rays back to the mirror
8. Draw a line connecting the object to the place on
the mirror where the reflected rays hit
9. Trace the VIRTUAL rays back behind the
mirror. The image appears where the rays meet
10. Use a protractor to construct the normal perpendicular to
the mirror at the point where the rays hit the mirror.
11. Measure both incident and reflected rays and compare
them using a percent difference
12. Label and measure the object distance and the
image distance. Using percent difference, compare
these two numbers
Results
a. Use this diagram to compare the incident angles
to the reflected angle
b. Use this diagram to compare image distance to
object distance
Doppler Effect
• The apparent change in a wave’s frequency due to
relative motion between the source and the
observer.
– Sound
– light
Lower frequency
away
Higher frequency
Shorter wavelength
Higher pitch
Longer wavelength
Lower pitch
towards
Polarization
• When a wave vibrates only in one plane
- up-down
- left-right
• ONLY transverse waves can be polarized
Classwork
• DO Pg 154-155 #26-47
• Read pg 156-158
– This is what we will talk about next period.
Superposition
• The piece by piece sum of two waves that meet in
the same place at the same time.
Constructive Interference
• When two crests OR two troughs meet to make a
larger crest/trough
Destructive Interference
• When a crest and a trough meet to produce nothing
– No light or sound
Resonance
Resonance is…
When a small amount of energy…
Added at the right frequency (called the
natural frequency)…
Produces a large amplitude…
resonance tuning forks
glass breaking 1
breaking glass 2
glass music
A typical microwave oven produces radiation at a frequency of 1.0 × 1010 hertz. What is the
wavelength of this microwave radiation?
1. 3.0 × 10-1 m
2. 3.0 × 10-2 m
3. 3.0 × 1010 m
4. 3.0 × 1018 m
When light rays from an object are incident upon an opaque, rough-textured surface, no
reflected image of the object can be seen. This phenomenon occurs because of
1. regular reflection
2. diffuse reflection
3. reflected angles not being equal to incident angles
4. reflected angles not being equal to refracted angles
At the instant shown, a cork at point P on the water's surface is moving toward
A
B
C
D
Electromagnetic radiation would be classified as
1. a torsional wave
2. a longitudinal wave
3. a transverse wave
4. an elliptical wave
Standing Waves Revisited
Do Now:
- What are the three conditions that need to be
met to produce a standing wave?
- An example of a standing sound wave
Rubens flame tube
HW MAKE A REVIEW SHEET
Sound as Music
- What is the relationship between frequency and
pitch?
- Think of a trombone, how does the pitch of the
sound change as the length of the slide increases?
- Based on this, how is frequency related to
wavelength?
• blue man group
– What do you notice about the length of the tubes and
the pitch of the waves? Does this confirm your
statement above?
Reflection Revisited
• Fixed end Reflection
– 180o phase change
• Free end Reflection
– No phase change
Incident
Crest
Incident
Crest
Reflected
Trough
Reflected
Crest
fixed and free end reflection
Resonance
Resonance is…
When a small amount of
energy…
Added at the right
frequency…
Produces a large
amplitude…
resonance tuning forks
glass breaking 1
breaking glass 2
glass music
Questions on the videos
•
•
•
Video 1
–
What type of wave would be produced in the ping pong balls when hit with the paddle?
–
What characteristic of sound does the frequency tell you about?
–
When is one tuning fork able to resonate with another? When doesn’t it work?
–
How does your radio work?
Video 2/3
–
why is the sound of the glass considered resonance?
–
What happened to the frequency when he added water?
–
What would happen to the sound wave’s wavelength when the water was added?
–
What would happen to the glass if he changed the frequency of the sound generator?
Video 4
–
What do you notice about the pitches of the sound and the size of the glasses?
–
Can you come up with an explanation of the relationship you wrote above?
•
Include wavelength and frequency in your explanation
Speed of Sound Lab
Goals:
1. To use the ideas of resonance, reflection, and
standing waves to determine the speed of sound in
the classroom.
Tuning fork
Setup
L
Movable tube open on both ends
Large tube filled with water
Procedure
1. Choose a tuning fork and note its frequency
in the data able.
2. Strike the tuning fork and hold it over the top
of the open tube. Raise the tube until you
reach the resonance point (you will hear the
sound get loud)
3. Measure the length of the hollow tube that is
above the water level.
4. Repeat for 2 other tuning forks.
Data
Frequency
(Hz)
Length of tube
above water
(m)
Diameter
correction
(m)
Wavelength of
the sound
wave (m)`
Speed of sound
(m/s)
Aim: What is refraction and how do we ?
DO NOW:
1. Name two different media
in this picture.
2. What happens to light as it
passes from one medium
to the other?
3. Offer an explanation as to
WHY you are seeing what
you see.
HW: Blue Book Review for test- all of waves
up to diffraction: pg
Refraction
• Refraction is the BENDING of a wave as is travels
from one medium to another.
• Remember: a wave changes speed when it moves
from one medium to another.
Frequency stays
the same when
traveling from one
medium to
another!!!
Index of Refraction
• The index of refraction is similar to the coefficient of
friction.
– It tells you how easily (quickly) light travels through a
substance
– It has no units
– The symbol for index of refraction is n
– The formula for the index of refraction is
c
n
v
– c is the speed of light in a vacuum (3x108m/s)
– v is the speed of light in the other medium.
– The index of refraction is ALWAYS GREATER THAN ONE!
Using the Index of Refraction
1. In which medium does light
move the fastest?
2. In which medium does light
move the slowest?
3. In which two mediums will
light have the same speed?
4. What is the speed of light in
water?
Derivations
• We Know
–𝒏 =
𝒄
which implies that 𝑐 = 𝑛1 𝑣1
𝒗
–𝒗 = 𝒇𝝀 which implies that 𝑣1 =f𝜆1
• c and f are constant when changing from one medium to
another so…..
𝑐 = 𝑛1 𝑣1 =𝑛2 𝑣2 which is written in your reference tables as
𝒏𝟐 𝒗𝟏 𝝀𝟏
=
=
𝒏𝟏 𝒗𝟐 𝝀𝟐
Example:
1. A light wave with a wavelength of 700nm in water enters flint glass.
a. What is the wavelength of the light in flint glass?
b. What is the speed of the light in the flint glass?
Snell’s
Law
• Used to calculate the angle of refraction as a wave
moves from one medium into another.
– Low to high index
• Speed decreases
• Wavelength decreases
• Angle bends towards the normal
– High to low index
• Speed increases
• Wavelength increases
• Angle bends away from the normal
𝒏𝟏 𝒔𝒊𝒏𝜽𝟏 =𝒏𝟐 𝒔𝒊𝒏𝜽𝟐
Is the speed of this wave increasing
or decreasing as it enters shallow
water?
Snell’s Law
Use a protractor
1. Air into water
θ1 = 38o
n1 = 1.00
n2 = 1.33
θ2 = ?
n1 = 1.00
𝒏𝟏 𝒔𝒊𝒏𝜽𝟏 =𝒏𝟐 𝒔𝒊𝒏𝜽𝟐
1.00𝑠𝑖𝑛38𝑜 =1.33𝑠𝑖𝑛𝜃2
0.463= 𝑠𝑖𝑛𝜃2
𝜃2 =27.6o
n2 = 1.33
Steps
1.
2.
3.
4.
5.
6.
Low to High!
Identify both indexes of refraction
Draw the normal line perpendicular to the surfaceLight bends
Measure the incident angle (θ1)
TOWARDS THE
Write your equation and plug in values with units!
Solve for the unknown angle (θ2 with units)
NORMAL!
Measure the angle from the normal line and construct it using
your protractor
AIM:
How do we apply Snell’s Law when finding the
index of refraction of a medium?
Remember, Snell’s Law:
n1 sin 1  n2 sin 2
Do Now:
sheet
Homework
-Make sure lab is complete
- finish packet
Do Now!
Finding the Index of Refraction
Goals: The goals of this lab include
to determine the index of refraction of the unknown
block using a graph
Background
write a PARAGRAPH explaining how refraction works
and what happens to all the parameters (speed,
wavelength, frequency) of a light wave as it moves
from one medium to another.
THINK!
based on the do now graph, what do we need to do to
determine the index of refraction of a block?
Procedure:
1. Trace the block on a sheet of paper
2. Remove the block and construct a normal line close to the
upper right hand corner
3. Using colored pencils, construct 5 incident rays at various
angles between 15o and 60o
4. Replace the block, and using a laser beam, sine the light along
one of the incident rays.
5. Locate that ray on the other side of the block and trace that ray
in the same color.
6. repeat for all 5 rays
7. Remove the block and connect the rays of the same color
8. Construct normal lines at each exit point and measure the
incident and refracted angles for each color!
9. Enter all angles in the data table
10.Graph sin θ1 vs. sinθ2 (what will the slope of this graph be?)
Finding the Index of Refraction
Normal line
Incident rays.
15o increments
Refraction
Block
Top view
Just like in the mirror lab, you will use a
laser beam to line up the ray while looking
THROUGH the block. Your line of sight
needs to be at table level! You can use
pins to help you line it up. Focus on ONE
color at a time
After
Normal line
Incident rays.
15o increments
Refraction
Block
Top view
Data
Color
θ1
(degrees)
Sin(θ1)
θ2
(degrees)
Sin(θ2)
Do Now!
Do Now
• Light is incident on a flint glass air boundary. The
light enters the air at the following angles
– 10o
– 20o
– 30o
– 40o
Flint glass
Air
• Using a ruler and protractor, find the refracted
angle for each incident angle. You can use colored
pencils to differentiate
Critical Angle Lab
• Goal:
– To use Snell’s Law and the ideas of refraction to
determine the critical angle of water.
– To verify the law of reflection
• Setup
refracted
Air
water
reflected
why don’t
these rays
bend when
they enter
the water?
Dispersion
• The separating of a light ray into its colors
– Caused by the refraction of light
– Each color has a slightly different index of refraction
which means that each color bends a little more than
the last causing a rainbow
Single Slit Interference
• Waves incident on a single
slit
– The central (center) maxima
(brightest spot) occurs in line
with the single slit.
– Each other small bright spot is
a location of constructive
interference due to the path
difference (1 wavelength) from
the lower edge of the slit and
the upper edge of the slit
Double Slit Interference
• Waves incident on 2 slits produce an interference
pattern with the central maxima between the two
slits, and each next maxima decreasing in intensity.
• Due to a path
difference between
the two slits.
Is light a wave or
is light a
particle!?!
Experiment 1:
Think: Light is incident on two closely spaced slits
and the pattern is observed on a wall or screen
across the room.
Wave: Water waves incident on two closely spaced
openings
Particle: Painted tennis balls are being thrown at a wall
through two closely spaced doors.
Young’s Double Slit Experiment
expectations
If light was a wave (think
water)…
•
•
•
•
If light was a particle (think
painted tennis balls)…
•
•
•
•
Double Slit
Experiment
Light behaving like a
wave.
Notice the light and
dark fringes.
What do the dark
spots represent?
What to the light
spots represent?
What do the spots
with no spots
represent?
Wave moving through
a double slit and
exhibiting interference
Young’s Double Slit
Experiment:
Shows that light
behaves like a wave
The Photoelectric
Effect:
Shows that light behaves
like a particle
The Great Debate
Wave
•
Particle
•
Is light a wave or is light
a particle!?!
AIM: How do we describe a particle of light?
• Do Now: what behavior shows light is a wave, why? What
behavior shows light is a particle why?
• HW: Blue Book
• pg 186-187 #1-11
• Pg 198-200 #1-5, 16-19, 34-35
• DUE THURSDAY!
What do we call a particle of
light?
A PHOTON!!
•
A photon is a small ‘packet’ of light
•
Any single photon has a fixed, discrete energy.
•
The intensity of visible light can be increased or
decreased only by changing the number of photons
present.
•
The same rules hold true for all electromagnetic waves
outside the visible range.
Discrete Energy??
• Discrete energy is like money, you can only have integer multiples of
a minimum amount.
– For money, what is this minimum amount?
• A photon can only carry integer numbers of a minimum energy
– This minimum energy is denoted by Planck’s constant
• h= 6.63x10-34Js
• Planck’s constant is modern physics’ version of the
penny
• The energy of a photon is determined by its frequency (and
wavelength)
E  hf
E
hc

Units
A joule is a large unit of energy. When you are talking about
small electron, we use an electron volt instead
-19
1eV=1.6x10 J
Ex1. A photon has 3.5eV of energy. How many Joules of
energy is that?
Ex2. A photon has 4.8x10-19J of energy, how many electron
volts is that?
Examples
1. A photon of light has a frequency of 2.5x1014 Hz.
-
What is the energy of that photon in Joules?
What is the energy of that photon in eV?
2. A photon has a wavelength of 575nm
-
What is the frequency of that photon?
What is the color of the photon?
What is the energy of that photon in Joules?
What is the energy of the photon in eV?
AIM: How has our understanding of
the atom changed over the years?
DO NOW: Draw AND label a diagram of an atom.
HW: HW: Blue Book
• pg 190-191 #12-34
• DUE TUESDAY
• QUIZ WEDNESDAY!
Atomic Structure
A brief History
Democritus- Greek Philosopher
~300BC
• The word atom means smallest piece.
Something that can not be divided.
• Atoms are made of the same ‘stuff’ but differ
in size and shape
• Atoms are in constant motion
• Atoms can combine to form different types of
matter
John Dalton
Late 1700s
• All elements are made up of atoms
• Atoms of the same element are all the same
but differ from atoms of different elements.
• Atoms can group together to form molecules
• Chemical reactions are changes in
combinations of atoms, not changes in the
individual atoms themselves.
JJ Thomson
late 1800s
• Measured the
charge/mass ratio of an
electron.
• Determined that an
electron had a negative
charge
• Could NOT determine the
actual mass or charge of
an electron.
• Plum pudding model of
the atom
Negative ‘plums’
Positive Goop
Rutherford-Geiger-Marsden
1911
• Gold foil scattering experiment
– Fired positively charged alpha particles (2 protons and 2
neutrons) at a thin foil of gold.
– Most alpha particles traveled straight through
• Most of an atom is empty space
– One day, one scattered at a wide angle as if it hit
something massive and dense.
• Holds most of the mass of an atom
• Must be positively charged
– This massive and dense thing was called the nucleus.
– An atom’s diameter is MUCH larger than that of the
nucleus.
Rutherford Scattering Setup
Most particles go straight through. A few
scatter and light up the screen at other
angles.
Bohr (Orbital) Model
• Electrons orbit around
a central nucleus
– The electron orbitals
have definite (discrete)
energy levels.
– Electrons can not exist
between energy levels.
• Similar to the fact that
you can not stand
between rungs of a
ladder.
Bohr (Orbital) Model
• Ground states
– Electrons want to fill the
lowest possible levels so that
the atom stays stable.
• Excited states
– Electrons can ‘jump’ up
energy levels only if the
correct amount of energy is
absorbed by the electron.
– This amount of energy is
determined by the energy
difference in the atom’s levels.
The Hydrogen Atom
1. What is the energy of the
n=3 energy level in the
hydrogen atom?
a. What is this energy in
Joules?
2. What is the energy difference
between the n=1 and n=4
energy levels?
Hydrogen Absorption Spectrum
When light is incident on a hydrogen atom, it can
absorb the photons with the correct amount of
energy that allow the electrons in the atom to
‘jump’ to their excited states. An absorption
spectrum is the rainbow of colors with the colors
matching the correct energy jumps missing.
Hydrogen Absorption Spectrum
1. Pick one of the missing colors
2. Determine a possible frequency of that color using
the RTs
3. Calculate the energy a photon of that color
4. Convert that photon’s energy into eVs.
5. Using your RTs decide which energy level
transition could be caused by that photon.
Hydrogen Emission Spectrum
Once an electron has reached the excited state by
absorbing the correct amount of energy. The electron
will stay there for a moment then return back down to
the ground state. When the electron falls back to the
ground state, it emits a photon with an energy equal
to the energy difference between the level it came
from and the level it went to.
Hydrogen Emission Spectrum
1. Pick a different color than before.
2. Determine a possible frequency of that color using
the RTs
3. Calculate the energy a photon of that color
4. Convert that photon’s energy into eVs.
5. Using your RTs decide which energy level
transition could be caused by that photon.
I was doing some particle physics research and I discovered 7
new elements. I knew that each element was different because
_______________________________________.
I was able to draw diagrams of each element’s energy levels to
scale, and I was able to name each element’s spectrum, but I
was not able to match the element’s energy level diagram to its
corresponding spectrum.
Your goal is to use the scaled drawing to figure out the letter of
that element based on the atomic spectra pictured.
a. Show all calculations in an organized manor including
formulas and units.
b. Choose a fourth color for the spectrum and add the
corresponding fourth energy level to the element’s
diagram. (it must be drawn to scale)
B
A
E
D
C
F
G
Nuclear Physics
Subatomic Forces and
Structures
Force
Name
Strong Force
Weak Force
Electromagnetic
Force
Gravitational
Force
Relative
Strength
Carrier
Carrier
symbol
Force
Range
Force
acts on
Zooming in on the
World Around Us
Macroscopically
• Gravity
–holds all objects with mass together (from stars to dust)
• Electromagnetic Force
–Holds the (negatively charged) electrons in orbit around the
(positively charged) nucleus of an atom
• Strong Force
– Holds all the positively charged protons and neutral neutrons
together in the nucleus
• Weak Force
–Holds all the quarks together in a proton and neutron
Microscopically
Creating Nuclear Energy
Mass or energy can never be created or destroyed,
only converted from one to the other!
E  mc
Fusion
• Two smaller elements
(anything below iron) fuse
together to create a larger
element.
• This is favored by nature
because this process
releases energy.
2
Fission
• One larger element
(anything above Iron) split
apart to create two smaller
elements.
• This is favored by nature
because this process also
releases energy
Fusion up Close
• For light elements (up to Iron), fusing two elements
together creates a larger element and energy.
• This energy comes from the ‘missing’ mass.
– The larger element has a smaller mass then the total mass of the
parts that make it up.
– The difference in mass is converted into released energy.
• This only happens in the sun and starts
Fission up Close
• An incident neutron causes a large unstable
element to split into smaller elements.
• When the element splits, some of the energy used
to hold the large nucleus is released.
• This happens in nuclear reactors around the world.
E=mc2
1. Which particle would generate the greatest amount
of energy if its entire mass were converted into
energy?
– electron
– proton
– alpha particle
– Neutron
2. If a proton was completely turned into energy, how
much energy would be released?
Mass Defect
• The mass of the individual protons and neutrons that make up an
element is larger than the actual mass of the element.
• This ‘mass defect’ is converted into the energy needed to hold the
nucleus together.
If the actual mass of the Lithium atom is 6.941u,
-What is the mass defect in u
-What is the binding energy in MeV?
-What is the binding energy in Joules?
The Standard Model of
Particle Physics
Things smaller than
protons and neutrons
Classification of Matter
Protons and
neutrons have 3
quarks, so they are
Baryons!
Quarks
• A proton is made
up of two up
quarks and a
down quark (uud)
• A neutron is made
up of two downs
and an up (udd)
Leptons
• Electrons are
leptons!
Antiparticles
• Antiparticles have the same mass as their particle ‘buddies’
just the opposite charge and quark make up.
• If a particle and an antiparticle collide, they annihilate each
other and all the mass is converted into energy.
1. What is the quark make up of an antiproton?
2. If a neutron and antineutron collide and annihilate each other,
how much energy is released in Joules?
Name ______________
Example Questions for
Modern Physics Unit.
• DO NOT LOSE THIS PACKET!
Young’s Double Slit Experiment
Expectations
If light was a wave (think
water)…
•
•
•
•
If light was a particle (think
painted tennis balls)…
•
•
•
•
The Photoelectric Effect
Expectations
If light was a wave (think water If light was a particle (think
bowling balls hitting the
hitting the fence)…
fence)…
•
•
•
•
•
•
•
•
The work function of a certain photoemissive material is 2.0 electronvolts. If 5.0-electronvolt photons are incident on the material, the maximum kinetic
energy of the ejected photoelectrons will be
1.7.0 eV
2.5.0 eV
3.3.0 eV
4.2.5 eV
Electromagnetic radiation of constant frequency incident on a photosensitive material causes the emission of photoelectrons. If the intensity of this radiation
is increased, the rate of emission of photoelectrons will
1. decrease
2. increase
3. remain the same
---------------------------------------------------------------------------------------------------------------------------------------------------------------------A joule is a large unit of energy when you are talking about small electrons. We use an electron volt instead
1eV=1.6x10-19J
Ex1. A photon has 3.5eV of energy. How many Joules of energy is that?
Ex2. A photon has 4.8x10-19J of energy, how many electron volts is that?
----------------------------------------------------------------------------------------------------------------------------------------------------------------------
1.
-
2.
-
A photon of light has a frequency of 2.5x1014 Hz.
What is the energy of that photon in Joules?
What is the energy of that photon in eV?
A photon has a wavelength of 575nm
What is the frequency of that photon?
What is the color of the photon?
What is the energy of that photon in Joules?
What is the energy of the photon in eV?
The Hydrogen Atom
1. What is the energy of the n=3 energy level
in the hydrogen atom?
a. What is this energy in Joules?
2. What is the energy difference between the
n=1 and n=4 energy levels?
Hydrogen Absorption Spectrum
1.
Pick one of the missing colors
2.
Determine a possible frequency of that color using the RTs
3.
Calculate the energy a photon of that color
4.
Convert that photon’s energy into eVs.
5.
Using your RTs decide which energy level transition could be caused by that photon.
I was doing some particle physics research and I discovered 7 new elements. I knew that each element was different because they
all had different atomic spectra. I was able to draw diagrams of each element’s energy levels to scale, and I was able to name
each element’s spectrum, but I was not able to match the element’s energy level diagram to its corresponding spectrum.
Your goal is to use the scaled drawing to figure out the name of that element based on the atomic spectra pictured below.
a.
b.
Show all calculations in an organized manor including formulas and units.
Choose a fourth color for the spectrum and add the corresponding fourth energy level to the element’s diagram. (it
must be drawn to scale)
Force Name
Strong Force
Weak Force
Electro-magnetic
Force
Gravitational Force
Relative
Strength
Carrier
Carrier
symbol
Force Range
Force acts on
Mass Defect
•
•
The mass of the individual protons and neutrons that make up an element is larger than the actual mass
of the element.
This ‘mass defect’ is converted into the energy needed to hold the nucleus together.
If the actual mass of the Lithium atom is 6.941u,
-What is the mass defect in u
-What is the binding energy in MeV?
-What is the binding energy in Joules?
E=mc2
1u=931MeV
1. Which particle would generate the greatest amount of energy if its entire mass were converted into energy?
–
–
–
–
electron
proton
alpha particle
Neutron
2. Approximately how much energy would be generated if the mass in a nucleus of an atom of were converted to energy? [The mass of is 2.0
atomic mass units.]
- 3.2 × 10-10 J
- 1.5 × 10-10 J
- 9.3 × 102 MeV
- 1.9 × 103 MeV
----------------------------------------------------------------------------------------------------------------------------------------------------------------------
Antiparticles have the same mass as their particle ‘buddies’ just the opposite charge and quark make up.
If a particle and an antiparticle collide, they annihilate each other and all the mass is converted into energy.
1.
What is the quark make up of an antiproton?
2.
If a neutron and antineutron collide and annihilate each other, how much energy is released in Joules?