Powerpoint presentation Q2

3. Speed of E.M. Spectrum Waves in a Vacuum
299,792,458 mls (3 x 108 m/s), or 186,000 miles per
second.
It takes about two and a half seconds, for instance, for a
radio communication traveling at the speed of light to get to
the moon and back.
• Speed decreases as density of medium increases
• Change in medium causes refraction (bending)
Atthis speed it can goaround the world 7.5 times in
one second

4. Thomas T. Amy, Explotalfons An IntrodWlm to Astronomy, 2nd sditlm. Cepyffgh 0 J996 The McGraw•HilI Compsnl•s, Inc. All rights reserved.
Electromagnetic Spectrum
Increasing energy
0.0001 0.01 nm
Increasing wavelength
10 nm 1000 nm 0.01 cm 1 cm 1 m
4‹A› nm 5‹Xt nm 6fXi nm

5. E
Electromagnetic Waves
Electromaqnetic Waves - energy-carrying
waves emitted by vibrating electrons
Light, Radiation, or Photons
s[>c•c -I - uvzzvc•l c njgtl-i x fr¢>qLuc•nczy
w e l l
are / ^“
http..'’csc.ssh.durkcIcy.odu.'’img.'’cri wave.gif

6. Cosmic rays
Background radiation; particles of enormous energy igven
off by stars.
Gamma radiation D
e
a y
dl high energy given out by the sun and other stars.
Xrays High energy used in e
Xd
ru
a e t.
Ultraviolet rays
Invisible energy waves in lvu
i h which cause skin to
tan.
Visible light
Basic colors of light, emitted by the sun and visible to
the human eye. R* GBIV.
Infrared rays Rays of heat ner ; sensed by our nervous system.
Radio waves f•licrowaves; TV; radio energy
Electromagnetic Spectrum

7. Radio Waves
Longest wavelength, lowest frequency (smallest
amount of energy)
• Used for radio, television, cellular phones,
cordless phones, radio astronomy, microwaves,
and RADAR
Types
Shortwave (for very long ranges)
AM (can bend around large objects such as
mountains)
FM (strong signals in range of about 50-70 miles)
Television broadcast waves (FM for sound and AM for
picture)

8. Infrared Radiation
• Heat
Thermograms show how much infrared
radiation is being given off a living thing
• Used to view objects in the dark
night vision goggles
Heat lamps use infrared radiation to heat
food

9. Visible Light
• Only part of the EM spectrum humans can see
4 x 1014 Hz to 7.9 x 1014 Hz
Visible spectrum of color (from longest
wavelength to shortest)
Red (650 nanometers)
Blue (470 nanometers)
(Indigo)
Violet (400 nanometers)

10. Visible
Lig
What we call light depends on the overall
sensitivity of the eye, ranging in
wavelength from 380 nm to 760 nm.

12. itravioiet Radiation
• Causes us to make vitamin D in our skin
• Can be harmful
can cause skin cancer
• Used to kill germs and sterilize medical
equipment
Nail shops
Safety goggles

13. rays
Their high energy makes then pass
through many materials
Various exposure times allows for
numerous views

14. Gamma Rays
• Most energetic
• Used in radiation therapy to kill cancer
cells

15. Important Properties of
Amplitude determines brightness
The greater the amplitude, the greater the
brightness
• Wavelength determines color
The waveenefh
becomes shorter
(9ed: aéout Y00 nmJ
(Blue:abouf §§0 nm)

16. I
ntensi
ty
Lig i nsity
• Intensity or brightness of the light changes
along with the colors
40 0 soo
W o v e l e n g th
60O
http://fuse. pha.jh u.edu/ wpb/spectroscopy/basics.html

17. uare L
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inverse SquareL
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http://www.anees.com/6.html
http://www.astrosociety.org/edu
cation/publications/tnI/32/starsci
ence2.html

18. Additive Primary of Lig
• overlapping or
“adding” various
colors of light
together almost
any color can be
made. Additive Primaries
RGB
Red, Green, and Blue
Light

19. Secondary of Light
•CoIors made by mixi
mary
•G & R =
R & B = magenta
B & G =
Magenta
htt ://www.colorado.edu/ sics/2000/tv/’coIortv.html
Yellow
Cyan

20. ixi (Additive)
• White light is formed where red, blue
and green light overlap
http://soI.sci.uop.edu/ jfalward/reflection/refIection55.html

21. Photons
Light and EM radiation are composed of
small particles called photons.
Photons are thought to be carriers of EM
force.
H
a
v
eeitherparticle orw
a
v
e
l
i
k
ebehavior.
This duality in the nature of photons is a
key aspect of Quantum theory.

22. Different Wavelengths
• Medium dictates speed
• Since the photon's energy does not
change, its frequency cannot change;
therefore its wavelength changes.
Wavelength decreases as the speed
decreases.

23. Particle Wave?
Particles are discrete
energy is concentrated into
what appears to be finite
space: is homogeneous with
definite boundaries
• Waves, notconsidered a
finite entity.
Light energy does not exist in
a single location, as a wave
v a r i e s i n b o t h p l a c e a n d t i m e .
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24. W
a
v
eTheory V
SParticleTheory
Photon-massless bundle of concentrated electromagnetic energy
• WaveTheory
Light acts like
waves ripples in
SpaCe
Particle Theory
Light acts like
particles that stream
from the source
(creating shadows)
fJ

25. ua ure
I
Proof that Light
is a wave
Proof of Nothing Proof that light
is a Particle
Diffraction
(particles don't change
direction as they pass BY
abarrier)
nterference
(two or more particles
can NOT exist in the
same place at the same
time)
•PoIarization
(polarized filters allow
light which is vibrating in
one direction through;
only transverse waves
can be polarized
RefIection
Refraction
PhotoeIectric
effect (When light hits
a photoemissive metal,
electrons are knocked off)
Proves light is a particle
since each photon knocks
loose one electron
•Compton
Effect ‹iight can
collide with small particles
& change their
momentum)

26. Duai Lig
a Wave-Particle Duality: not
strictly one or the other
a Quantum electrodynamics
(QED) combines the wave-
particle nature of light into a
single theory.
» Light behaves as a wave
When light travels through an
opening
a Light behaves as particles
when light bounces off of metal
http //nobe prize org
/nobeI prizes/physic
s/art cles/ekspong/in
dex.html
http://new.c cs.k12.ny.us/physics/n
otes/ madern/ modern note.hI m

27. Photoeiectric effect
•The photoelectric effect refers to the emission, or
ejection, of electrons from the surface of,
generally, a metal in response to incident light.
Discovered by
Einstein in the early
20th century
electrons are ejected from
a solid when impinged
upon by electromagnetic
radiation
excitation
led to the understanding
of light as particles, or
photons
htjp./'.' .physics.uiowa.ed>’adven ure'’falJ
200'2’oct 15 05.htmI
hjp!.''.' uwsp.edu!geo'’facuI y'’itte‹/'geog101''textbook.'’enet
gy.'’nature of electromagnetic radiations 2.hmm

28. Lig as a Particle
Photoelectric Effect
UC Berkel ey 's Diqital Chem1A
http://www-inst.eecs.berkelev edu/ cs39j/sp02/session07.html

29. Polarization
The process of transforming non-polarized light
into polarized light is known as polarization.
Polarized light waves are light waves in which
the vibrations occur in a single plane.
http://www.gIenbrook.k12.iI.us/gbssci/phys/Class/light/u12I1e.html

30. Light reflected from a
horizontal surface is
partially polarized in the
horizontal plane.

31. Polarized Light wave not particle
e Light consists of
transverse waves
having components
that are perpendicular
to the direction of
propagation.
http://www.olympusmicro.com/primer/lightandcolor/p
artideorwave.html
ya‹tIcksandWrvesTh‹o«ghc‹oesedpokrlzers

32. Polarized Lenses Really
Make a Difference!
Light reflected from
surfaces like a flat road or
smooth water is generally
horizontally polarized.
Vertically oriented
polarized lenses result in
a reduction in glare.
Eliminate reflected glare
Enhance contrast
Great for use during snow or
water sports
htlp:.'’.'’www.spyoptic.com.'’img.'’42:19 tridentPoIarized.jpg

33. Areyourlensespolarized?
http://www.agape1.com/polarized.htm
R
O
A
D
CL0SID

34. http.//www.3d 1assesonline.ci›m/how-do-3d-
glasses-w'ork/inilCx.himl
iasses
T
w
oprojectors project t
w
o
respective views onto the
screen
each with a different
polarization.
The glasses are polarized
oppositely
allowing only one image into
each eye

35. < !/ Idle Law ofIteflection ep
e
t
ot
h
em
i
r
r
o
r
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eb
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a
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›o
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‹eflected offthemirror is
calledthersIle‹:t âI›«n.
be a
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eb
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M
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e
nt
h
ei
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c
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e
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tb
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a
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thenormal is calledtheangle a/incidence.
T
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f
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c
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a
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thenormal is talled theam
pleofreflection.

36. Law Refiection
Angle of
incidence is equal
to angle of
reflection
I = incoming light
N = Normal
R = Reflected light

37. Reflected Lig
(»'°»'u'°'•6'•'°)
• SPECULAR REFLECTIONlight is reflected in
the same forward direction only
DIFFUCE REFLECTION light is reflected in
many directions

38. reflect m a n y cJifferent an
e e
fes.
ght beams
ca
refiection because
deemed tow Qyour y s f
noc añ g t h erejected !i
Re@$d§@r raf?ectio
UOP on the
reflected at t*e
surface.
same angle. When your eye
Tight b e a m s are
detects the reflected beams. YOU Can see a ref lec-

39. Total Internai Refiection
• Occurs when light
travels from a
medium of larger to
smaller index of
refraction
the light ray can
actually bend so
much that it never
goes beyond the
boundary between
the two media
Cnbcal Ray

40. Total internai Refiection
If the fish looks upwards it
sees the sky, but if it looks
at too large an angle to the
vertical it sees the bottom of
the pond reflected on the
surface of the water.
The critical angle to the
vertical is equal to the
critical angle for total
internal reflection at an air-
water interface which is
approximately 49O
.

41. ota nterna eflection
Refracted ray
hLtp://www.glen
brook.k12.iI.us/g
bssci/plys/CLass
/refrn/u1413b.ht
ml

42. Fiber Optics
Fiber-optic lines are strands of optically pure
glass as thin as a human hair
The light in a fiber-optic cable travels through
the core (hallway) by constantly bouncing
from the cladding (mirror-lined walls)
total internal reflection

43. Refraction
http://fr.wikipedia,org/wikifRfiCà7aA9fraction

44. The Law Refraction
The law of refraction is used to predict the amount
of bend, or refraction.
The law of refraction is also known as Snell's Law,
named for Willobrord Snell, who discovered the law
in 1621.

45. More Refraction
• Assuming that the air
on both sides of a
window have the
same refractive
indices
Then the incoming
and outgoing light
beams are actually
parallel

46. Snell's Law
http //www op org/ icy/education/Teachift§ 9éLâfikgfiCñ8'1t
ngTo20Advanced%20Physics/Vibrations9o20and9o20Waves/Refiecti
on%20and%20refraction/page 447T.html
The relationship between the angles of
incidence and refraction and the indices of
refraction of the two media involved.

47. Bending Towards the Normai
• ex: light passing
from air into water
lower to higher
density
• the angle of
refraction is smaller
than the angle of
incidence
http:// id.mind.net/
efr6ction1.html
zona/mstm/physics/lighgrayOptics/refraction/r

48. Bendi A
w
a
yFrom theNormai
ex: light passing from
water into air
higher to lower density
• the angle of refraction is
larger than the angle of
incidence.
http://id.mind.n
e
w-zona/mstm/physics/light/rayOptics/refraction/refractio
n1.html

49. Exampies
that create a
Spectrum
Prism
Raindrops
• CD's
objects
Diffraction rating
The tracks of a compact disc
act as a diffraction grating,
producing a separation of the
colors of white light

50. Yellowish
White

51. s
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52. Transparent Materials
• object through which light can pass
in straight lines
EinorJ*,ont liay
http:/.*www.gcsescience.com/’pwav21. htm

53. Clear glass is transparent to visible light but
not to infrared light; therefore trapped heat!
http://www.ucolick.org/bolte/AY400/week2/lipht sidetripsC.html

54. Visible Lig Infrared
• Clear glass is transparent to Visible light.
• Absorbed, converted, emitted as Infrared.
• Clear glass is not transparent to Infrared
Light.
Trapped infrared light increases interior
temperature.

55. Opaque Materials
• ue the term applied to
materials that absorb light
http:/’/www.ronbigelow.co
m/articies/color
perception 2.’perception
2.htm

56. Transl Material
Allows some light to pass through
• ex: a filter or tinted glass
Incident Light
Transiiined
http://www.ronbigelow.com/articles/color-perception-2/perception-2-6.jpg

57. Shadows
• Umbra - the darker
part of a shadow
where all the light is
blocked
Penumbra a partial
shadow