WAVES: SOUND & LIGHT

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Nov 29, 2013 (3 years and 8 months ago)

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WAVES: SOUND & LIGHT

Waves carry energy from one place to
another

© 2000 Microsoft Clip Gallery

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
.



© 2000 Microsoft Clip Gallery

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

© 2000 Microsoft Clip Gallery


© 2000 Microsoft Clip Gallery


Transverse Waves


Energy is perpendicular to direction of
motion


© 2000 Microsoft Clip Gallery

Compression or Longitudinal
Waves

Electromagnetic Spectrum

© 2000 Microsoft Clip Gallery

Electromagnetic Spectrum


Visible Spectrum


Light we can see


Roy G. Biv


Acronym for Red,
Orange, Yellow, Green, Blue, Indigo, &
Violet.


Largest

to
Smallest

Wavelength.

Radio Waves


Invisible Spectrum


Longest wavelength &
lowest frequency.


Also emitted by Stars
and gases



Dangers
:


Radio wave
sickness


Cancers
-

leukemia

© 2000 Microsoft Clip Gallery

Modulating Radio Waves


AM





Carries
audio

for T.V. Broadcasts


Longer wavelength so can bend
around hills


FM




Carries
video

for T.V. Broadcasts

© 2000 Microsoft Clip Gallery

Infrared Rays


Invisible Spectrum (Cont.)


Light rays with longer wavelength than red light.


Our skin emits infrared rays


Far infrared = hot ; Shorter infrared = cool


Uses
: Cooking, Medicine, T.V. remote controls,
military


thermal imaging, astronomy and
weather forecasts, heat lamps for sports medicine


Dangers


Too much exposure = overheating

Infrared: Thermal Imaging

Microwave



Basically high frequency radio waves


Used in satellite communication and transmission, radar
systems and microwave cooking/microwave oven


travels in straight line without losing much of its energy


Dangers
:


Prolonged exposure



causes cataracts



Cell phones may cause



Brain damage



(tumors)

speed
-
monitoring
radar

satellite station

Ultraviolet Rays


Invisible spectrum (cont.).


Humans can’t see, but some insects can


EM waves with frequencies slightly higher than visible light


USES
: tanning beds, astronomy, food processing & hospitals to kill germs,
attracts insects (kills them), detecting counterfeit money, whitening teeth,
hardening dental
fillings,black

light, helps your body produce Vitamin D


Ozone layer blocks most UV from getting to earth


DANGERS
:


UV
-
B CHANGES DNA IN CELLS


CANCER


SKIN AND EYE DAMAGE, SUNBURN

X
-
RAYS



Invisible Spectrum


.High frequency waves


An X
-
ray machine works by firing a beam of electrons at a
"target". If we fire the electrons with enough energy, X
-
rays
will be produced.



Uses
: Medicine


Bones absorb x
-
rays; soft tissue does
not., airport security, astronomy



Lead absorbs X
-
rays

Dangers
:


Cancer, Cell damage e
sp. in first trimester for fetus

AIRPORT X
-
RAY MACHINE

GAMMA RAYS


Invisible spectrum (cont.)


Highest frequency EM waves; Shortest
wavelength. They come from outer space.


Uses
: cancer treatment, radioactive tracers,
sterilize foods through irradiation.


Dangers
:


Kills all living cells


Causes cancer


Only lead or concrete will block


Visible light



Seen by the human eye



Uses: fiber optics, medical
procedures, telecommunications,
chemical spectral analysis and
photosynthesis, endoscopy.
Lasers for medical, industrial and
surveying use.


CD's and DVD's, Laser printers,


Dangers
: Too much light can
damage retina

laser surgery

Visible Light cont’d

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.)

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.

© 2000 Microsoft Clip Gallery

OPAQUE


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.

© 2000 Microsoft Clip Gallery


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
color

© 2000 Microsoft Clip Gallery

Human Eye Diagram

LIGHT & ITS USES


Sources of Light


Incandescent light


light produced
by heating an
object until it
glows.

© 2000 Microsoft Clip Gallery

© 2000 Microsoft Clip Gallery

LIGHT & ITS USES


Fluorescent

Light




Light produced by electron
bombardment of gas molecules


Phosphor coating absorb photons
that are created when
mercury

gas
gets zapped with electrons. The
phosphors glow & produce light.

© 2000 Microsoft Clip Gallery

LIGHT & ITS USES
-

Neon


Neon

light


neon inside glass
tubes makes red
light. Other
gases make other
colors.

© 2000 Microsoft Clip Gallery

Compact Fluorescent lights


Energy Efficient


Designed to replace incandescent lights


Must be disposed of properly


DANGERS
:


Mercury poisoning


Destroys neurons

LIGHT & ITS USES
-

Reflection


Reflection



Bouncing

back of light
waves


LIGHT & ITS USES:

Reflection Vocabulary


Real Image




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


Formed in locations where light
does NOT reach


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

© 2000 Microsoft Clip Gallery

LIGHT & ITS USES: Mirrors


Plane Mirrors


Perfectly flat


Actually a
Virtual Image


Erect


Image is right side up

© 2000 Microsoft Clip Gallery

LIGHT & ITS USES: Mirrors


Reflection & Mirrors (Cont.)


Convex

Mirror


Curves
outward


Reduces
images.


Uses
: Rear view mirrors, store
security…

CAUTION! Objects are closer than they appear!

© 2000 Microsoft Clip Gallery

LIGHT & ITS USES: Lenses


Convex

Lenses


Thicker

in the center than edges.


Lens that
converges

(brings together) light rays.


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
enlarged
.

© 2000 D. L. Power

CONVEX

CONCAVE

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.

© 2000 Microsoft Clip Gallery

© 2000 Microsoft Clip Gallery

LIGHT & USES: Lenses

Vision



Human 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

© 2000 Microsoft Clip Gallery

© 2000 Microsoft Clip Gallery

© 2000 Microsoft Clip Gallery

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.
Breaks images into bands of light & dark and colors.


Each element has it's own unique
'fingerprint
' of color


Scientist identify stars based on the color emitted