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Electromagnetic WavesChapter 3
Electromagnetic Spectrum Lesson 3-1
http://arc.iki.rssi.ru/mirrors/stern/Education/wemwaves.html
Types of Waves
Longitudinal Waves
Transverse Waves
http://www.thetech.org/exhibits/online/quakes/waves/p&s_waves.html
Longitudinal Waves
Longitudinal Waves: one in which the disturbance is parallel to the line of travel of the wave. Cannot travel through empty space. The wavelength depends on the frequency.
http://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/waves/u10l1c.html#vocab
Longitudinal Wave
When a longitudinal wave moves through a material, the particles of the material move backwards and forwards along the direction in which the wave is travelling. Below is a picture of a longitudinal wave travelling along a spring.
http://www.glenbrook.k12.il.us/GBSSCI/PHYS/mmedia/waves/lw.html
http://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/waves/u10l1c.html#vocab
Longitudinal Wave
Example of Longitudinal Wave
Sound Waves
Sound is always produced by something vibrating. The vibrations will make matter - either solid, liquid or gas - near it vibrate. In this way, energy is taken away from the source of the vibrations.
Sound must cause another object to vibrate to be detected.
Sound cannot travel in a vacuum because there is nothing (no matter) for the vibrations to pass through.
Sound does not travel in outer space.
– When you see movies or TV shows about battles in outer space, you should only be able to see an explosion but not hear it. The sounds are added for dramatic effect.
• Sound waves exist as variations of pressure in a medium such as air. They are created by the vibration of an object, which causes the air surrounding it to vibrate. The vibrating air then causes the human eardrum to vibrate, which the brain interprets as sound.
Sound Facts• Sound must cause another object to vibrate
to be detected. • Sound travels fastest through things that
have tightly packed atoms: solids. • The speed of sound is slower in liquids than
solids, and slowest in gases. • The speed of sound in air is around 340 m/s,
in water about 1500 m/s and in solids around 5000 m/s.
• Lightning causes thunder. The delay between them happens because the speed of light is nearly 1,000,000× that of sound in air.
Example of Longitudinal WaveUltrasound
Ultrasound is sound that is above the range of human hearing. It even travels at exactly the same speed as sound in any medium. Taking a ultrasound of the unborn fetus is a lot safer then taking an x-ray.
http://www.ob-ultrasound.net/
Ultrasounds are used in many different ways from looking at valves of the heart, cleaning teeth and airplane wings to taking sonar to determine the depth of water.
http://upload.wikimedia.org/wikipedia/commons/7/74/Valves_Of_Heart_Ultrasound.gif
Valves Of Heart Ultrasound
Example of Longitudinal WaveP- Wave (Primary Waves)
In an earthquake P-waves are longitudinal waves that push and pull the earth. They are the fastest body wave, averaging speeds of about 6 km/s, so arrive first.
http://samjshah.com/2008/07/30/earthquakes-richter-scale-and-logarithms/
Transverse Waves
Transverse Waves: one in which the disturbance is perpendicular to the direction of travel of the wave.
http://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/waves/u10l1c.html#vocab
Transverse Waves• Most waves are transverse waves.
– Such as water waves, S-waves, electromagnetic waves
http://www.earthquakes.bgs.ac.uk/earthquakes/education/eq_booklet/dia_seismic_s_waves.jpg
http://visual.merriam-webster.com/images/science/physics-optics/electromagnetic-spectrum.jpg
Example of Transverse WavesS-waves (Secondary Waves)
In an earthquake S-waves are transverse waves which make the earth shake from side to side. Slower than P-waves, they average about 4 km/s so arrive second
http://samjshah.com/2008/07/30/earthquakes-richter-scale-and-logarithms/
The highest point on the wave is called the crest.
The lowest point on the wave is called the trough.
Transverse Wave
http://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/waves/u10l1c.html#vocab
Wavelength – the distance between one wave crest to the next.
Amplitude – the deepest part of a trough or the highest part of a peak is called the amplitude
Transverse Wave
http://images.google.com/imgres?imgurl=http://www.ewart.org.uk/science/waves/wave.jpg&imgrefurl=http://www.ewart.org.uk/science/waves/wav1.htm&h=141&w=300&sz=10&hl=en&start=3&usg=__T80Pq8VdL2vTd0w99Gt8k5MUCek=&tbnid=wpxOXIn-PSw5EM:&tbnh=55&tbnw=116&prev=/images%3Fq%3Dparts%2Bof%2Ba%2Btransverse%2Bwave%26gbv%3D2%26hl%3Den%26safe%3Dactive&safe=on
Transverse WaveFrequency – the number of waves per
second, measured in hertz
http://www.indiana.edu/~emusic/acoustics/frequency.htm
Transverse WaveWavelength and frequency are inversely
proportional. (when one gets larger the other gets smaller.) As the frequency of a wavelength increases the wavelength get shorter.
http://www.qrg.northwestern.edu/projects/vss/docs/Communications/1-what-is-frequency.html
Electromagnetic Waves• Electromagnetic waves are transverse waves that
have some electrical and magnetic properties. They do not need a medium, matter, to travel through.
• Electromagnetic waves transfer energy by means of changing electric and magnetic fields.
Electromagnetic wave is a combination of electric fields and magnetic fields that are turning at right angles to each other.
http://images.google.com/imgres?imgurl=http://www.geo.mtu.edu/rs/back/spectrum/e_mag.gif&imgrefurl=http://www.geo.mtu.edu/rs/back/spectrum/&h=268&w=506&sz=5&hl=en&start=14&usg=__4gowTVPqnhNWawjtYLi3zSGocyQ=&tbnid=BLYdvKWr6t5XfM:&tbnh=69&tbnw=131&prev=/images%3Fq%3Delectromagnetic%2Bwaves%26gbv%3D2%26hl%3Den%26safe%3Dactive&safe=on
It begins with a vibrating electric charge that
produces an electric field which produces a
magnetic field which produces an electric field
which produces a magnetic field that changes
direction with each vibration of the charge.
http://physicsclub.net/physletIndex/waves.html
Electromagnetic waves are formed when an electric field (shown as blue arrows) couples with a magnetic field (shown as red arrows). The magnetic and electric fields of an electromagnetic wave are perpendicular to each other and to the direction of the wave. James Clerk Maxwell and Heinrich Hertz are two scientists who studied how electromagnetic waves are formed and how fast they travel.
http://science.hq.nasa.gov/kids/imagers/ems/waves2.html
Electromagnetic waves come in many wavelengths and frequencies. Each one is useful in different ways.
Electromagnetic Waves
http://science.hq.nasa.gov/kids/imagers/ems/index.html
Every time the source of an electromagnetic wave vibrates, it creates one wave that moves away from the source at the speed of light, 300 million meters per second.
Electromagnetic Waves
http://mynasadata.larc.nasa.gov/images/EM_Spectrum3-new.jpg
Frequency = Speed/Wavelength
Wavelength Verses Frequency
Wave Source Wavelength Frequency
AM Radio 500 m
VHF TV 5.0 m
FM Radio 3.33 m
UHF TV 1.0 m
Radar 0.03 m
Visible Light 0.0000005 m
X-Ray 0.000000009 m
Electromagnetic SpectrumElectromagnetic Spectrum – the entire range of
electromagnetic waves– Parts of the spectrum have names (from
lowest frequency to highest frequency)• Radio waves• Microwaves• Infrared Radiation• Ultraviolet Radiation- Visible Light is at
the beginning of ultraviolet radiation• X Rays• Gamma Rays
– Radiation is the transfer of energy by electromagnetic waves
http://www.andor.com/learning/light/
Electromagnetic Spectrum
Nature of Light
http://images.google.com/imgres?imgurl=http://selfpursuit.com/wp-content/uploads/2007/08/wp-contentuploadsspectrum.jpg&imgrefurl= http://selfpursuit.com/45/discovering-peace-through-noise/&h=334&w=485&sz=13&hl=en&start=47&um=1&usg=__HdJMnSWxOQYSCB4sT-xIPjoTysk=&tbnid=MRy0izUjbafcEM:&tbnh=89&tbnw=129&prev=/images%3Fq%3DNature%2Bof%2Blight%26start%3D40%26ndsp%3D20%26um%3D1%26hl%3Den%26safe%3Dactive%26sa%3DN&safe=on
Visible Light – only small portion of the electromagnetic spectrum
Light is a wave and consists of small particles called quanta
Who discovered the colors of white light?
Clue:1. Discovered over 300 years
ago.2. Passed a beam of white
light through a prism.3. First took apart white light
and then put it back together.
4. Initials I. N.5.
http://images.google.com/imgres?imgurl=http://inversesquare.files.wordpress.com/2007/12/sir_isaac_newton_1702.jpg&imgrefurl=http://inversesquare.wordpress.com/2007/12/14/friday-isaac-newton-blogging-an-apple-tree-of-knowledge/&h=599&w=481&sz=100&hl=en&start=4&um=1&usg=__Wm9rKyZL80BdhaDm08qE-oKNpeo=&tbnid=1bI6ZFu2XYro6M:&tbnh=135&tbnw=108&prev=/images%3Fq%3Disacc%2Bnewton%26um%3D1%26hl%3Den%26safe%3Dactive&safe=on
Prism
Sir Isaac Newton
http://images.google.com/imgres?imgurl=http://school.discoveryeducation.com/clipart/images/prism4c.gif&imgrefurl=http://school.discoveryeducation.com/clipart/clip/prism4c.html&h=300&w=400&sz=17&hl=en&start=43&um=1&usg=__QlbK9xGP5VhMlwQv5-y3ppE_s-w=&tbnid=8hrTSnYWs4flwM:&tbnh=93&tbnw=124&prev=/images%3Fq%3Dprism%26start%3D40%26ndsp%3D20%26um%3D1%26hl%3Den%26safe%3Dactive%26sa%3DN&safe=on
ColorThe only color signals the brain receives are
red, green and blue stimuli
http://home.att.net/~RTRUSCIO/SPECTRUM.htm
ColorBlack is the color of objects that do not reflect
light in any part of the visible spectrum; they absorb all frequencies of light.
White light is all colors, can be separated into a rainbow of colors
http://library.thinkquest.org/27066/color/nlchanges.html
ReflectionLight travels in straight lines and can be reflected off
surfaces
When the ray of light reflects off a flat surface, the angle of incidence is equal to the angle of reflection.
http://www.glenbrook.k12.il.us/gbssci/phys/mmedia/optics/lr.html
DiffractionDiffraction – the bending of light around a
barrier.– Waves bend in a semi-circular pattern as they
pass the barrier.
http://www.olympusmicro.com/primer/lightandcolor/diffraction.html
Refraction of LightRefraction of Light - occurs as light passes
from one medium to another only when there is a difference in the index of refraction
http://csep10.phys.utk.edu/astr162/lect/light/ref-diff.html
http://micro.magnet.fsu.edu/primer/lightandcolor/refractionintro.html
BibliographyAbramowitz, Mortimer, and Michael W. Davidson. "Diffraction of Light." Olympus
Microscopy Research Center. 2000-2008. Olympus Microscopy Research Center. 24 Oct. 2008 <http://www.olympusmicro.com/primer/lightandcolor/diffraction.html>.
Glencoe/McGraw-Hill Team. Teacher's for Use with Science Interactions Course 3. 3rd ed. New York: Glencoe/McGraw-Hill, 1998. 80+.
Harmsworth, A. P. "Waves: Sound, Ultrasound, P-Waves, S-Waves." GCSE Physics. 2005-2008. GCSE Physics. 24 Oct. 2008 <http://www.gcse.com/waves/sound.htm>.
Henderson, Tom. "The Nature of a wave." Glenbrook South Physics Teachers. 1996-2008. Glenbrook South. 24 Oct. 2008 <http://www.glenbrook.k12.il.us/gbssci/phys/class/waves/u10l1c.html#vocab>.
Kurtus, Ron. "Sound Waves." School for Champions. 26 June 2005. School for Champions. 24 Oct. 2008 <http://www.school-for-champions.com/science/sound.htm>.
Sample, Sharron. "What are Electromagnetic Waves?" National Aeronautics and Space Administration. 27 Mar. 2007. NASA Official. 24 Oct. 2008 <http://science.hq.nasa.gov/kids/imagers/ems/waves2.html>.