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Energy transfer through different mediums can be explained using wave and particle models

From the Australian Curriculum, Year 9 Science.
by

Gerald Carey

on 31 January 2016

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Transcript of Energy transfer through different mediums can be explained using wave and particle models

Absorbed
Energy transfer through different mediums can be explained using wave and particle models.
Waves
Two Types of Waves
Transverse
Longitudinal
(Compression)

Sound Waves
Frequency
Hertz
Pitch
Wavelength
Amplitude
Investigation 9.1 p 305 Jac
Must travel through a medium (e.g. air)
Move through different substances at different speeds
Sonar
Ultrasound
Investigation 9.2 Jac p 307
Hearing
Intensity
decibels (dB)
Structure of the ear
Outer
Middle
Inner
Sound thresholds
Hearing aids
Cochlear implants
Investigation 9.3 Jac p 310
Investigation 9.4 Jac p 311
The Electromagnetic Spectrum
Gamma Rays
Radiowaves
Infrared
Visible
Ultraviolet
X-Rays
Microwaves
Arranged according to frequency of the wave
Characteristics
Electromagnetic waves
Travel through a vacuum
Travel at speed of light
Are
disturbances
in
electric
and
magnetic
fields that exist in space

http://www.hk-phy.org/energy/domestic/heat_phy/flash/heat_transfer3.swf
Nice demo of this concept particularly in the third tab
Carry electric and magnetic energy
Carry kinetic energy
(an example of a
Longitudinal
wave)
Fields caused by particles that contain an
electric charge
Moving charges
create these electric and magnetic fields
These fields can extend out great distances from the charges that create them
Image: group of students with hands out (representing charge) spread out so none are touching.
Image: one moving student (a moving charge) moves through the students and they spread out before him. But when he leaves they move back to fill in the gaps.
(ie moves like a wave)
Interactive Summary here: http://www.pbs.org/wgbh/nova/assets/swf/1/electromagnetic-spectrum/electromagnetic-spectrum.swf
Can
reflect
off surfaces, travel through the surface and be
absorbed
by the material or be
transmitted
through the material.

Waves that are reflected or transmitted from a substance, take their energy with them.
Are absorbed by a substance may be transformed into a different form.
http://www.mmscrusaders.com/newscirocks/energy/electromagnetic%20waves.pdf
For example, Light is absorbed by plants and used in photosynthesis
Light is then reflected and transmitted and is
green
coloured

Light Waves
Rays
Reflect
This material is
transparent
This material is
translucent
This material is
opaque
Refract
Optical Fibres
Radio Waves
Transmission
Reception
FM v AM
TV
Mobiles
Communication through...
Wireless
Electricity
Light
Radio
Microwaves
Heat Energy
Conduction
Convection
Radiation
Kinetic energy
Insulators
Convection Current
Radiant Heat
Reflected
Electricity
Electric charge
Atomic Structure
Electric Circuits
Conducting Paths
Current and Voltage
Circuit diagrams
Parallel
Series
Ammeter
Voltmeter
Inquiry Investigation 10.8 Jac p363
Batteries
Inquiry Investigation 10.10 & 11 Jac p370 -1
http://science.howstuffworks.com/humans-hear-in-space1.htm
How the sound of a bell travels in the air
Go here for a much more detailed table of speed of sound through different media: http://physics.info/sound/
Write down your prediction!
Write down your prediction!
Animation show movement of sound waves through solid, liquid and gas.
(Start at 1 min 41 sec mark - about half way)
Student demonstration of why a medium (e.g. air) is needed to carry sound.
Warning: annoying sound!
Breaking glass by sound energy
Sound that has frequencies higher than humans can hear
Uses of ultrasound
Can also be used for cleaning, healing muscles and even cutting materials!
Sending high frequency sound towards another object and measuring how long it takes for the sound wave (or echo) to return.
Also used by bats, dolphins and...humans
Shipwreck found using sonar
Demonstration of longitudinal waves
Introduction to radiation
Introduction to Wave/Particle duality - only show near the end!
Features include:
Sound waves
Sound waves
Sound waves
Scientifically called "media" e.g. air, water, glass
Uses of Sound
Ultrasound
Uses for Sound
A characteristic of waves
A characteristic of waves
A characteristic of waves
Longitudinal waves
Another name for Frequency is 'period'
The frequency (or period) of a vibration or wave is the number of complete vibrations or waves made in one second.
Units used to measure frequency
Middle C in music is 256 Hertz (Hz)
In sound, high frequency notes produce sounds of high pitch.
http://teachertube.com/viewVideo.php?video_id=27013
Video showing changes in frequency and pitch.
Use Audacity to demonstrate this!
Animation to show how we hear
http://www.childrensuniversity.manchester.ac.uk/interactives/science/brainandsenses/ear/
Normal hairs in cochlea
Damaged hairs in cochlea
Baby able to hear for the first time
How the cochlear works
Frequency for
Sound waves of higher amplitude are louder.
More molecules at the crest of the wave
Fewer molecules at the crest of the wave
Another way to represent this:
Crest: more molecules closer together
Trough: more molecules further apart
Amplitude: half the difference between the crest and the trough
Be careful - this type of graph is also used to represent another type of wave called a transverse wave (e.g. light waves)
This is what is being represented in the above graph.
Phet has a useful simulation: http://phet.colorado.edu/en/simulation/sound
Really good simulation with some good explanations: http://www.iknowthat.com/ScienceIllustrations/sound/science_desk.swf
Simulations for student use
This simulation shows the link between the two ideas
http://faraday.physics.utoronto.ca/IYearLab/Intros/StandingWaves/Flash/long_wave.html
Wavelength calculator: http://www.mcsquared.com/wavelength.htm
Enter the frequency in Hertz and it will tell you how long the wave is in metres.
In Sound, wavelength is the distance between maximum compressions. It is linked to frequency.
It can also be 'represented' like this:
Here is middle C from Wikipedia: http://en.wikipedia.org/wiki/C_(musical_note)
Here are some other frequencies to 'play' - http://www.mindspring.com/~scottr/zmusic/
What happens when we lose our hearing?
Used to help make sounds louder for those that are hearing impaired.
How hearing aids work
Is and electronic connection between an external microphone and the cochlear
Used for those who are profoundly deaf
Measurement of sound levels
Units are in...
130 dB can cause pain and permanent ear damage
120 dB makes humans uncomfortable
0 dB is the lower limit of HUMAN hearing
Why does light slow down when going through glass
The types of waves we are about to meet actually travel as 'waves' that we might see in water.
This is different to the longitudinal sound waves.
Type of wave
Type of wave
Includes
All of which move (or are transmitted) as
Transverse Waves
Electromagnetic waves
Electromagnetic waves
(well, mostly)
Electromagnetic waves
Unlike Sound and other Mechanical waves e.g. water waves
Features of
The first discovery of electromagnetic waves other than light came in 1800, when William Herschel discovered infrared light.
1800: William Herschel
1801: William Herschel
1895 Wilhelm Roentgen
1898 Paul Villard
1887 Henrich Hertz
1864 James Maxwell
Electromagnetic waves
Electromagnetic waves
Electromagnetic waves
Lower energy
Less danger to human
s
Higher energy
Much more danger to humans
Electric fields exist in any particle with a positive or negative charge.
Magnetic fields arise from the motion of electric charges
Most building materials shield electric fields to some extent
Most building materials
do not
shield
m
agnetic fields to some extent
More to do with electricity but...
NASA's introduction to Electromagnetic waves
Magnetic lines of force
Great simulation of radio transmission and reception
http://phet.colorado.edu/en/simulation/radio-waves
The only form of electromagnetic radiation that humans can detect
Some birds and insect can 'see' ultraviolet light
Some snakes and insects can detect infrared light
Light waves travel in straight lines called
Light rays bounce off a reflective object (e.g. a mirror) at the same angle as they hit the object.
The first known example of electromagnetic waves
Infrared image of a mouse
When light rays are blocked, shadows form:
Light waves can...
...pass through material e.g. glass
Light waves can...
Light waves can...
...be scattered by material e.g. frosted glass
...be reflected or absorbed by material e.g. wood
Light waves can...
You can see through it, but not clearly
Light waves can..
Practical on Light
Light rays can...
When light travels through a substance that is transparent or translucent, it can speed up or slow down.
If light hits the translucent or transparent surface at an angle, the light will bend.
Light ray
Air
Water
Objects appear distorted due to light refraction
Practical on spoons and mirrors
Practical on coins and refraction
Are thin glass tubes that don't allow light to escape
How optic fibres use total internal reflection
Gets a bit technical at about the 2:30 mark
Is light a wave or particle?
For no reason at all, here is an interesting wave
PhET demonstration: http://phet.colorado.edu/en/simulation/bending-light
Bent light ray
Slinky as an example of a longitudinal or compression wave.
Nice experiment on confusing colours
http://www.thenakedscientists.com/HTML/content/kitchenscience/exp/confusing-colours/
Activity showing reflection of light rays in low light
http://www.thenakedscientists.com/HTML/content/kitchenscience/wierd/light/exp/ghostly-windows/
Activity to make a simple electromagnet:
http://www.thenakedscientists.com/HTML/content/kitchenscience/wierd/light/exp/electromagnet/
Measuring the size of wavelengths (note: needs a microwave, bread, butter and two plates) http://www.thenakedscientists.com/HTML/content/kitchenscience/wierd/light/exp/measuring-the-speed-of-light/
Make a pinhole camera (note: needs a head-size box, pins of different sizes and paper) http://www.thenakedscientists.com/HTML/content/kitchenscience/exp/pinhole-camera/
Pitch and Frequency activity (Note: needs string, heavy weights, blocks of wood and a table) http://www.thenakedscientists.com/HTML/content/kitchenscience/exp/string-guitar/
Radio waves can be made artificially by vibrating electrons in a metal transmitter
Radio waves can be detected by a metal receiver (antenna) The metal atoms vibrate rapidly in response.
Are waves that can have an extremely low frequency (3 kHz to extremely high frequency (300 GHz)
...is transmitted as radio waves. One wave carries the vision and another carries the audio signal.
...also transmit their signals as low energy microwaves.
Summary of Radio Frequency and how they are used in society.
Really nice interactive wave simulation.
Use it to create both types of waves
http://outreach.physics.utah.edu/labs/waves/wave_basics/waves.htm
Summary of Radio Frequency and how they are used in society.
Optical fibre
Light houses
Traffic lights
Neon lights
Communication towers
Non-mobile phones
Nervous systems
Platypus sensing prey
Can produce weird effects on corn starch!
Ultrasound
...is energy on the move from one region to another at a lower temperature
...is the movement of heat energy through a medium by vibrating atoms
Just watch the first 30 seconds...
Interesting simulation. Student make a prediction about the conductive properties of three metals.
http://kids.britannica.com/lm/labunits/activities/Unit_9/product.html
Particles in a region of
high temperature
vibrate more quickly than particles in nearby regions of
lower temperature
.
36.5 C
32.2 C
26.7 C
23.8 C
Most solids conduct heat better than liquids and gases because the atoms are closer together in a solid
Metals are the best conductors of heat.
Materials that don't conduct heat are called 'insulators' and include foam, wool, air and fibreglass
Conductors
...is the rapid transfer of heat energy by the movement of
liquid
and
gas
particles.
Are important in houses e.g. to circulate warmth.
includes the movement of hot air/water to regions of colder air/water.
How about this for heat: Solar flares in slo-mo.
Using a small fish tank filled with water placed over a bowl of hot water and a bowl of ice, the convection currents can be seen using red and blue food dye.
Heat energy
Conduction
Convection currents
Do Inquiry 10.2 Jac p 345
is the release of energy by electromagnetic radiation
No medium e.g. air, water is needed
Radiation can be
Radiation can be
Radiation can be
Transmitted
is the transfer of radiation from one object to another
In this picture, what percentage of sunlight is
Transmitted?
Absorbed?
or Reflected?
First summative practical on radiation
s
Try Think Questions 9-13 Jac p 348
Static electricity
Excess of electrical charge (electrons) on the surface of an object
Current electricity
Movement of electrical charge from an area of high charge to an area of lower charge usually through a circuit.
Good summary - show at the end
Flow of electricity
between two points
because of a difference in electrical charge.
The difference in potential electrical charge between
two
points.
Voltage causes current
Nice simulation here: http://www.dynamicscience.com.au/tester/solutions/electric/circuits1.htm
Nice simulation showing the difference between series and parallel: http://www.dynamicscience.com.au/tester/solutions/electric/circuits2.htm
Go here to see a simulation showing the difference:
http://www.physics-chemistry-interactive-flash-animation.com/electricity_electromagnetism_interactive/hydraulic_analogy_difference_voltage_current.htm
How to use a Multimeter: http://www.physics-chemistry-interactive-flash-animation.com/electricity_electromagnetism_interactive/multimeter.htm
How to use a Multimeter: http://www.physics-chemistry-interactive-flash-animation.com/electricity_electromagnetism_interactive/multimeter.htm
Good simulation: http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel_pre_2011/electricityintheory/voltagecurrentresistancerev4.shtml
Current (I) is measured by an Ammeter
The units are in Amps (A)
Voltage (V) is measured by a Voltmeter between two points.
Voltage is measured in Volts (V)
The flow of electrical current can be
slowed
by the type of material the current is traveling in e.g. copper wire
Resistance
This is called it's
resistance
(r).
Resistance
is measured in Ohms ( )
Metals have low
resistance,
insulators have high
resistance
This simulation (http://phet.colorado.edu/en/simulation/ohms-law) illustrates the connection between all three concepts
An explanation of the three concepts
Metal atom
Free electrons
Electrons are bound loosely to the metal atom and are 'free' to move
Electron flow through a circuit
Are symbolic ways to show items in a circuit
Consist of two or more conductive items that provide a
path for electrons to flow
when a current is applied.
light
lead
Two or more items connected to a power supply that can allow the flow of electrons from one point to another
A
break
along
any part
of the conducting path will
stop
the flow of electrical current
Go here for an online circuit diagram creator: https://www.circuitlab.com/editor/
light
lead
(for practice)
Bubble Wrap, newspaper, cotton wool, plastic, foil, chux wipes,
Choose one!
Do steps 1 and 4 at the same time
Results:
add your results to the results table.
construct two lines graphs in your book.
Here is the summative part:
You need to design an experiment using the template given to
compare the amount of heat that is radiated
over a time period from silver, white and black aluminum cans
containing water at the same temperature
.
Is where current can flow along
two or more separate
conducting paths
Is where current can flow along
one
conducting path.
Common symbols for circuit diagrams
Make pretty patterns at different pitches
Why does you voice sound different when recorded?
Lightening strike in slo-mo
Interactive Ear
http://www.amplifon.co.uk/interactive-ear/index.html
More sound and music experiments
What happens when you light a match?
http://gfm.aps.org/meetings/dfd-2014/5404ec5f69702d0771a40100
Incredible video showing a match being lit in slow motion. Look for the heated currents of air from the match (and the human at the end)
Another way to look at it:
http://www.kurzweilai.net/a-new-visualization-of-the-electromagnetic-spectrum#!prettyPhoto
Heat loss in the human body
Full transcript