Waves

WAVES: SOUND & LIGHT
Waves carry energy from one place to another
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NATURE OF WAVES
Waves (Def.) – A wave is a disturbance that transfers energy.

Medium – Substance or region through which a wave is transmitted.

Speed of Waves – Depends on the properties of the medium.

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SAMPLE LESSON: Light & the Electromagnetic Spectrum
By D. L. Power
Revised 1/20/01
© 2000 Microsoft Clip Gallery
Albert Einstein
LIGHT: What Is It?
Light Energy
Atoms
As atoms absorb energy, electrons jump out to a higher energy level.
Electrons release light when falling down to the lower energy level.
Photons - bundles/packets of energy released when the electrons fall.
Light: Stream of Photons
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Electromagnetic Waves
Speed in Vacuum
300,000 km/sec
186,000 mi/sec
Speed in Other Materials
Slower in Air, Water, Glass
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Transverse Waves
Energy is perpendicular to direction of motion
Moving photon creates electric & magnetic field
Light has BOTH Electric & Magnetic fields at right angles!
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Electromagnetic Spectrum
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Electromagnetic Spectrum
Visible Spectrum – Light we can see
Roy G. Biv – Acronym for Red, Orange, Yellow, Green, Blue, Indigo, & Violet.
Largest to Smallest Wavelength.
Electromagnetic Spectrum
Invisible Spectrum
Radio Waves
Def. – Longest wavelength & lowest frequency.
Uses – Radio & T.V. broadcasting.
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Modulating Radio Waves
Modulation - variation of amplitude or frequency when waves are broadcast
AM – amplitude modulation
Carries audio for T.V. Broadcasts
Longer wavelength so can bend around hills
FM – frequency modulation
Carries video for T.V. Broadcasts
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Short Wavelength Microwave
Invisible Spectrum (Cont.)
Infrared Rays
Def – Light rays with longer wavelength than red light.
Uses: Cooking, Medicine, T.V. remote controls
Electromagnetic Spectrum
Invisible spectrum (cont.).
Ultraviolet rays.
Def. – EM waves with frequencies slightly higher than visible light
Uses: food processing & hospitals to kill germs’ cells
Helps your body use vitamin D.
Electromagnetic Spectrum
Invisible Spectrum (Cont.)
X-Rays
Def. - EM waves that are shorter than UV rays.
Uses: Medicine – Bones absorb x-rays; soft tissue does not.
Lead absorbs X-rays.
Electromagnetic Spectrum
Invisible spectrum (cont.)
Gamma rays
Def. Highest frequency EM waves; Shortest wavelength. They come from outer space.
Uses: cancer treatment.
LIGHT: Particles or Waves?
Wave Model of Light
Explains most properties of light
Particle Theory of Light
Photoelectric Effect – Photons of light produce free electrons
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LIGHT: Refraction of Light
Refraction – Bending of light due to a change in speed.
Index of Refraction – Amount by which a material refracts light.
Prisms – Glass that bends light. Different frequencies are bent different amounts & light is broken out into different colors.
Refraction (Cont.)
Refraction-Spectroscope Lab
Hey girls! The filters go on the Spectroscope, not on the lashes!
© 2000 D. L. Power
Color of Light
Transparent Objects:
Light transmitted because of no scattering
Color transmitted is color you see. All other colors are absorbed.
Translucent:
Light is scattered and transmitted some.
Opaque:
Light is either reflected or absorbed.
Color of opaque objects is color it reflects.
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Color of Light (Cont.)
Color of Objects
White light is the presence of ALL the colors of the visible spectrum.
Black objects absorb ALL the colors and no light is reflected back.
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Color of Light (Cont.)
Primary Colors of Light
Three colors that can be mixed to
produce any other colored light
Red + blue + green = white light
Complimentary Colors of Light
Two complimentary colors combine
to make white light-Magenta,Cyan,Yellow
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How You See
Retina –
Lens refracts light to converge on the retina. Nerves transmit the image
Rods –
Nerve cells in the retina. Very sensitive to light & dark
Cones –
Nerve cells help to see light/color
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Paint Pigments
Pigments absorb the frequency of
light that you see

Primary pigments
Yellow + cyan + magenta = black
Primary pigments are compliments
of the primary colors of light.
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Complementary Pigments
Green, blue, red
Complimentary pigments are primary colors for light!
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LIGHT & ITS USES
Sources of Light
Incandescent light – light produced by heating an object until it glows.
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LIGHT & ITS USES
Fluorescent Light –
Light produced by electron bombardment of gas molecules
Phosphors absorb photons that are created when mercury gas gets zapped with electrons. The phosphors glow & produce light.
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LIGHT & ITS USES - Neon
Neon light – neon inside glass tubes makes red light. Other gases make other colors.
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LIGHT & ITS USES - Reflection
Reflection – Bouncing back of light waves
Regular reflection – mirrors smooth surfaces scatter light very little. Images are clear & exact.
Diffuse reflection – reflected light is scattered due to an irregular surface.
LIGHT & ITS USES:
Reflection Vocabulary
Enlarged –
Image is larger than actual object.
Reduced –
Image is smaller than object.
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LIGHT & ITS USES:
Reflection Vocabulary
Erect –
Image is right side up.
Inverted –
Image is upside down.
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LIGHT & ITS USES:
Reflection Vocabulary
Real Image –
Image is made from “real” light rays that converge at a real focal point so the image is REAL
Can be projected onto a screen because light actually passes through the point where the image appears
Always inverted
LIGHT & ITS USES:
Reflection Vocabulary
Virtual Image–
“Not Real” because it cannot be projected
Image only seems to be there!
Light & Its Uses: Mirrors
Reflection Vocabulary
Optical Axis – Base line through the center of a mirror or lens
Focal Point – Point where reflected or refracted rays meet & image is formed
Focal Length – Distance between center of mirror/lens and focal point
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LIGHT & ITS USES: Mirrors
Plane Mirrors – Perfectly flat
Virtual – Image is “Not Real” because it cannot be projected

Erect – Image is right side up
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LIGHT & ITS USES: Mirrors
Reflection & Mirrors (Cont.)
Convex Mirror
Curves outward
Enlarges images.
Use: Rear view mirrors, store security…
CAUTION! Objects are closer than they appear!
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LIGHT & ITS USES: Lenses
Convex Lenses
Thicker in the center than edges.
Lens that converges (brings together) light rays.
Forms real images and virtual images depending on position of the object
LIGHT & ITS USES: Lenses
Convex Lenses
Ray Tracing
Two rays usually define an image
Ray #1: Light ray comes from top of object; travels parallel to optic axis; bends thru focal point.
Focal Point
Lens
Object
© 2000 D. L. Power
LIGHT & ITS USES: Lenses
Convex Lenses
Ray Tracing
Two rays define an image
Ray 2: Light ray comes from top of object & travels through center of lens.
Ray #1
Ray #2
© 2000 D. L. Power
LIGHT & ITS USES: Lenses
Concave Lenses –
Lens that is thicker at the edges and thinner in the center.
Diverges light rays
All images are erect and reduced.
© 2000 D. L. Power
How You See
Near Sighted – Eyeball is too long and image focuses in front of the retina
Far Sighted – Eyeball is too short so image is focused behind the retina.
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LIGHT & USES: Lenses
Concave Lenses –
Vision – Eye is a convex lens.
Nearsightedness – Concave lenses expand focal lengths
Farsightedness – Convex lenses shortens the focal length.
LIGHT & USES: Optical Instruments
Cameras
Telescopes
Microscopes
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LIGHT & USES: Optical Instruments
LASERS
Acronym: Light Amplification by Stimulated Emission of Radiation
Coherent Light – Waves are in phase so it is VERY powerful & VERY intense.
LIGHT & USES: Optical Instruments
LASERS
Holography – Use of Lasers to create 3-D images
Fiber Optics – Light energy transferred through long, flexible fibers of glass/plastic
Uses – Communications, medicine, t.v. transmission, data processing.
LIGHT & USES: Diffraction
Diffraction – Bending of waves around the edge of a barrier. New waves are formed from the original. breaks images into bands of light & dark and colors.
Refraction – Bending of waves due to a change in speed through an object.
LIGHT & USES: Diffraction
A diffraction grating. Each space between the ruled grooves acts as a slit. The light bends around the edges and gets refracted.
© 2000 Microsoft Encarta
SAMPLE STUDENT PROJECT: Diffraction Grating Glasses (Pd. 1)
© 2000 D. L. Power
© 2000 D. L. Power
SAMPLE STUDENT PROJECT: Diffraction Grating Glasses (Pd. 3)
© 2000 D. L. Power
SAMPLE STUDENT PROJECT: Diffraction Grating Glasses (Pd. 3)
are you hard at work or hardly working?
Hey girls,
© 2000 D. L. Power
SAMPLE STUDENT PROJECT: Diffraction Grating Glasses (Pd. 5)
Note: There’s more posing than working!
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SAMPLE STUDENT PROJECT: Diffraction Grating Glasses (Pd. 5)
© 2000 D. L. Power
SAMPLE STUDENT PROJECT: Diffraction Grating Glasses (Pd. 5)
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SAMPLE STUDENT PROJECT: Diffraction Grating Glasses (Pd. 6)
© 2000 D. L. Power
SAMPLE STUDENT PROJECT: Diffraction Grating Glasses (Pd. 6)
© 2000 D. L. Power
EVALUATION: State Standards
Waves carry energy from one place to another
Identify transverse and longitudinal waves in mechanical media such as spring, ropes, and the earth (seismic waves)
Solve problems involving wavelength, frequency, & speed.
.
EVALUATION: State Standards
Radio waves, light, and x-rays are different wavelength bands in the spectrum of electromagnetic waves whose speed in vacuum is approximately 3x10 m/sec
Sound is a longitudinal wave whose speed depends on the properties of the medium in which it propagates.
EVALUATION: State Standards
Identify the characteristic properties of waves:
Interference
Diffraction
Refraction
Doppler Effect
Polarization.
 
References
http://www.scimedia.com/chem-ed/light/em-spec.htm, updated 2/1/97
 
http://encarta.msn.com/find/Concise.asp?ti=06AFC000
 
http://www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSpec2.html
 
http://www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSpec.html
 
http://www.physics.sfasu.edu/astro/color.html#linkshttp://www.physics.sfasu.edu/astro/color.html#links
 
http://www.isc.tamu.edu/~astro/color.html
 
References
http://www.scimedia.com/chem-ed/light/em-rad.htm, updated 11/22/97
 
http://www.isc.tamu.edu/~astro/color.html
 
http://www.isc.tamu.edu/~astro/color.html
 
http://www.holo.com/holo/cmpany/laserart.htmlhttp://www.holo.com/holo/cmpany/laserart.html
 
http://www.holo.com/holo/book/book1.html#defhttp://www.holo.com/holo/book/book1.html#def
 
 
WORKS CITED
http://www.scimedia.com/chem-ed/light/em-rad.htm, updated 11/22/97  

http://www.scimedia.com/chem-ed/light/em-spec.htm, updated 2/1/97  

http://encarta.msn.com/find/Concise.asp?ti=06AFC000
 
http://www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSpec2.html
 
http://www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSpec.html
 
http://www.physics.sfasu.edu/astro/color.html#linkshttp://www.physics.sfasu.edu/astro/color.html#links
 
http://www.isc.tamu.edu/~astro/color.html
 
http://www.isc.tamu.edu/~astro/color.html
 
http://www.isc.tamu.edu/~astro/color.html
 
http://www.holo.com/holo/cmpany/laserart.htmlhttp://www.holo.com/holo/cmpany/laserart.html
 
http://www.holo.com/holo/book/book1.html#defhttp://www.holo.com/holo/book/book1.html#def
 
The End…
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