http://arc.iki.rssi.ru/mirrors/stern/Education/wemwaves.html
Electromagnetic Waves
Chapter 3
Electromagnetic Spectrum
Lesson 3-1
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
Longitudinal Wave
http://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/waves/u10l1c.html#vocab
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 Wave
Ultrasound
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.
Valves Of Heart Ultrasound
http://upload.wikimedia.org/wikipedia/commons/7/74/Valves_Of_Heart_Ultrasound.gif
Example of Longitudinal Wave
P- 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-andlogarithms/
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 Waves
S-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-andlogarithms/
Transverse Wave
The highest point on the wave is called
the crest.
The lowest point on the wave is called
the trough.
http://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/waves/u10l1c.html#vocab
Transverse Wave
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
http://images.google.com/imgres?imgurl=http://www.ewart.org.uk/science/waves/wave.jpg&im
grefurl=http://www.ewart.org.uk/science/waves/wav1.htm&h=141&w=300&sz=10&hl=en&start
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Transverse Wave
Frequency – the number of waves per
second, measured in hertz
http://www.indiana.edu/~emusic/acoustics/frequency.htm
Transverse Wave
Wavelength 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
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gnetic%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
Electromagnetic waves come in many
wavelengths and frequencies. Each one
is useful in different ways.
http://science.hq.nasa.gov/kids/imagers/ems/index.html
Electromagnetic Waves
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.
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 Spectrum
Electromagnetic 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
Electromagnetic Spectrum
http://www.andor.com/learning/light/
Nature of Light
Visible Light – only small portion of the
electromagnetic spectrum
Light is a wave and consists of small particles
called quanta
http://images.google.com/imgres?imgurl=http://selfpursuit.com/wp-content/uploads/2007/08/wpcontentuploadsspectrum.jpg&imgrefurl= http://selfpursuit.com/45/discovering-peace-throughnoise/&h=334&w=485&sz=13&hl=en&start=47&um=1&usg=__HdJMnSWxOQYSCB4sTxIPjoTysk=&tbnid=MRy0izUjbafcEM:&tbnh=89&tbnw=129&prev=/images%3Fq%3DNature%2Bof%2Blight%26start%3D40%26n
dsp%3D20%26um%3D1%26hl%3Den%26safe%3Dactive%26sa%3DN&safe=on
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_isa
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wton%26um%3D1%26hl%3Den%26safe%3Dactive&safe=on
Prism
http://images.google.com/imgres?imgurl=http://school.discoveryeducation.com/clipart/images/prism4c.gif&i
mgrefurl=http://school.discoveryeducation.com/clipart/clip/prism4c.html&h=300&w=400&sz=17&hl=en&star
t=43&um=1&usg=__QlbK9xGP5VhMlwQv5-y3ppE_sw=&tbnid=8hrTSnYWs4flwM:&tbnh=93&tbnw=124&prev=/images%3Fq%3Dprism%26start%3D40%26nds
p%3D20%26um%3D1%26hl%3Den%26safe%3Dactive%26sa%3DN&safe=on
Sir Isaac Newton
Color
The only color signals the brain receives are
red, green and blue stimuli
http://home.att.net/~RTRUSCIO/SPECTRUM.htm
Color
Black 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
Reflection
Light 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
Diffraction
Diffraction – 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 Light
Refraction 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
Bibliography
Abramowitz, 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. 19962008. 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-forchampions.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>.