Post on 01-Jun-2018
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Reflection and Refraction
Physics
Mrs. Coyle
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Reflection
When a wave reaches a boundary it is:
Partially reflected (bounces off surface)Partially transmitted through surface.
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aw of Reflection
!ngle of incidence " !ngle of reflection
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#ote
$ %he angle of incidence is formedbetween the incident ray and thenormal.
$ %he angle of reflection is formedbetween the reflected ray and thenormal.
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iffuse Reflection
$ Reflection from a rough surface.
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https://reader010.{domain}/reader010/html5/0604/5b149b8f6b2bc/5b149b951ae19.jpg
http://micro.magnet.fsu.edu/primer/java/reflection/specular/specularjavafigure1.jpghttp://micro.magnet.fsu.edu/primer/java/reflection/specular/specularjavafigure1.jpg8/9/2019 Reflection and Refraction .ppt
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Reflection from a Plane Mirror
di=do
hi=ho
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%y'e of mage
$ Real or *irtual
$ +nlarged or Reduced
$ +rect or nverted
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What is the minimum mirrorheight re,uired for a 'ersonto see their full self in the
mirror-
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int: Com'are !/ to C
A
D
B
C
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Refraction
$ When a wave crosses a boundarybetween Medium 0 and Medium 12 thewave changes direction because itchanges velocity.
$ 3re,uency remains constant.
$ *elocity changes as a result ofwavelength change.
$ &imulations
$ htt':44www.walter5fendt.de4'h06e4refraction.htm 7777777
$ htt':44www8.interscience.wiley.com:904legacy4college4halliday46;081.htm
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Refraction
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+>am'le
Less Rigid
Medium
More RigidMedium
Refracted
ray bendstowards
thenormal.
Incident
Ray
Refracted Ray
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nde> of Refraction2 n
n = c / v
$ c :the s'eed of light in a vacuum28 > 09 m4sec
$ v : s'eed of light in the medium.
$ n: medium?s inde> of refraction
$ n>1 (hy!"
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Indices of Refraction
*acuum 0.
!ir 0.8
Water 0.88+thanol 0.8=
Crown glass 0.
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#ote
$ %he s'eed of light has a lower s'eedin a more o'tically dense medium.
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Problem
$ What is the s'eed of light in ,uartA-
$ !nswer: 0.B; > 0 9 m4s
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&nells aw
$ n1 sin 1 = n# sin
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#ote
When the incident ray travels from
a less o$tically dense medium(low n"
to
a more o$tically dense medium
(higher n"
then the refracted ray bends
towards the normal.
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Problem
$ What is the angle of refraction whena ray from air with an angle ofincidence of 1< o is incident to water-
$ raw the ray diagram.
$ !nswer: 09.
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%otal nternal Reflection
$ Can occur when ray goes fromhighern to lowern.
$ !bove a Critical angle (of incidence)the ray is reflected2 not refracted
$ htt$://www.walter%fendt.de/$h1&e/refraction.htm
$ 3or 'roblems2 set the angle ofrefraction to B2 and solve for criticalangle
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Problem
$ 3ind the critical angle for a light raythat is incident from water to air.
$ !nswer: 69.9 o
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is'ersion$ %he inde> of refraction of glass is different
for the colors that maDe u' white lightbecause the s'eed of light is slightlydifferent in glass for each fre,uency oflight. (n vacuum all colors have s'eedc"8>09m4s.)
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Problem
%he inde> of refraction for crownglass for red light is 0.
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Mirage
http://www.warren-
wilson.edu/~physics/PhysPhotOfWeek/!!"PPOW/!!"!#1$oad%irage/&%'(
1)))%irage*rop+!!.jpg
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Mirage%otal internal reflection occurs because
hot air has a lower n2 than cold air.
http://www.warren-wilson edu/~physics/PhysPhotOfWeek/!!"PPOW/!!"!#1$oad%irage/inde, html