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>.