?? 4 :????????????? Lab.4 - Refraction, Polarization, Interference and Diffraction of Light

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?? 4 ?????????????Lab.4 - Refraction,
Polarization, Interference and Diffraction of
Light

• To observe the various phenomena of light
• To study some important foudatmental optical
  principles.
• A. Refraction Index of Prism (???????)
• B. Polarization of Light (????)
• C. Thin-Film Interference of Air Wedge (????????)
• D. Multi-reflective Interference in Glass
  (???????????)
• E. Diffraction of Light (????)

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2. ?????????????????????????????,???????????????,????
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3. ???????,???????????,??????????????,???????????????
   ??????????,???????????????????????
4. ???????????????,????????,???????????????,?????????
   ???
5. ????????????????????,??????????????????????????,??
   ?????????????,????????

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??????????????Ref http//www.phys.ncyu.edu.tw/y
gwu/lasar_safety.doc

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I. Laser Safety Rulers

• Class 1 Lasers
• A warning sign indicating the laser
  classification should be placed in a visible
  location on the laser.
• Class 2 Lasers
• Do not stare at the laser or permit any person to
  stare at the laser beam.
• Do not point the laser at a person's eye.

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Class 3 Lasers

1. Never aim a laser beam at a person's eye.
2. Use proper safety eyewear if there is a chance
   that the beam or hazardous specular reflection
   will expose the eyes.
3. Only experienced personnel should be permitted to
   operate the laser. Never leave an operable laser
   unattended if there is a chance that an
   unauthorized person may attempt to use it. A key
   switch should be used. A warning light or buzzer
   should indicate when the laser is operating.
4. Enclose as much of the beam path as possible.
5. Avoid placing the unprotected eye along or near
   the beam axis as attempted in some alignment
   procedures since the chance of hazardous specular
   reflection is greatest in this area.
6. Terminate the primary and secondary beams if
   possible at the end of their useful paths.
7. Use beam shutters and output filters to reduce
   the beam power to less hazardous levels when the
   full output power is not required.
8. Make sure that any spectators are not potentially
   exposed to a hazardous condition.
9. Attempt to keep laser beam paths above or below
   either sitting or standing position eye level.
10. Operate the laser only in a well-controlled area.
    That is, in a closed room with no windows and
    controlled access.
11. Label lasers with appropriate Class III danger
    statements and placard hazardous areas with
    danger signs.
12. Mount the laser on a firm support to assure that
    the beam travels along the intended path.
13. Assure that individuals do not look directly into
    a laser beam with optical instruments unless a
    adequate protective filter is present.
14. Eliminate unnecessary specular (mirror-like)
    surfaces from the vicinity of the laser beam path.

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Class 4 Lasers

• Enclose the entire laser beam path if at all
  possible. If this is done, the laser device could
  be considered to be a less hazardous
  classification.
• Confine indoor laser operation to a light-tight
  room with interlocked entrances to assure that
  the laser cannot emit when a door is open.
• Insure that all personnel wear adequate eye
  protection, and if the laser beam irradiance
  represents a serious skin or fire hazard that a
  suitable shield is present between the laser beam
  and the any persons in the room.
• Use remote firing and video monitoring or remote
  viewing through a laser safety shield where
  feasible.
• Use beam traverse and elevation stops on outdoor
  laser devices to assure that the beam cannot
  intercept occupied areas or intercept aircraft.
• Use beam shutters and laser output filters to
  reduce the laser beam irradiance to less
  hazardous levels whenever the full beam power is
  not required.
• Assure that the laser device has a key-switch
  master interlock to permit only authorized
  personnel to operate the laser.
• Install appropriate signs and labels on
  entrances, switches and anywhere an unauthorized
  person might mistakenly activate the laser.
• Remember that optical pump systems may be
  hazardous to view and that once optical pumping
  systems for pulsed lasers are charged, they can
  spontaneously discharged, causing the laser to
  fire unexpectedly.
• Use dark, absorbing diffuse, fire-resistant
  targets and backstops where feasible.

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Refraction Index of Triangular Prism(???????)

• Object To measure the refraction index of prism.
• Principle referred from http//hyperphysics.phy-a
  str.gsu.edu/hbase/hframe.html, Light and
  Vision, in web site HyperPhysics, hosted by
  the department of Physics and Astronomy, Georgia
  State University, GA, US
• A-1 Refraction of Light
• Refraction is the bending of a wave when it
  enters a medium where it's speed is different.
  The refraction of light when it passes from a
  fast medium to a slow medium bends the light ray
  toward the normal to the boundary between the two
  media. The amount of bending depends on the
  indices of refraction of the two media and is
  described quantitatively by Snell's Law.
• -be responsible for image formation by lenses
  and the eye.

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Refraction of Light Index of Refraction
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Snells Law
Total Internal Reflection
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(No Transcript)
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Refraction of Prism
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Angle of Minimum Deviation of Prism
--Provides a good way to measure the index of
refraction of a material.
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Applications of Prism

• A refracting prism is a convenient geometry to
  illustrate dispersion and
• The use of the angle of minimum deviation
  provides a good way to measure the index of
  refraction of a material.
• Reflecting prisms are used for erecting or
  otherwise changing the orientation of an image.
• Making use of total internal reflection instead
  of refraction.

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Experimental Procedures

1. Let laser beam horizontally incident to the wall
   or a white paper which has a distance of about
   0.5 m far away. To mark the position of laser
   beam.
2. Settle the triangular prism on the optical
   platform with the U-shaped support device and
   angular scale disc. To adjust the proper position
   of prism to locate the path of laser beam.
3. Rotate the prism slowly and observe the deviation
   path of the refracted laser beam by prism. To
   mark the beam position when the angle of
   deviation through a prism is minimum.
4. Prisms are typically characterized by their angle
   of minimum deviation d. This minimum deviation is
   achieved by adjusting the incident angle until
   the ray passes through the prism parallel to the
   bottom of the prism.

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Experimental Procedures

1. To measure the distance of the both positions
   marked by step (1) and (3), and the distance
   between the prism and the screen of laser spot.
   To calculate the angle of minimum deviation, ?,
   for the prism based on the formula above.
2. Change the incident angle of laser into the prism
   and repeat the procedures (2) to (4), to get the
   other the angle of minimum deviation, ?.
3. To measure the apex angle of the prism ?.
4. To determine the refraction index of the prism.

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B. Polarization of Light (????)