Download 偏振、干涉和繞射(Optical).

實驗 4 :光的折射、偏振、干涉和繞射
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 (三稜鏡的折射率)
B. Polarization of Light (光的偏振)
C. Thin-Film Interference of Air Wedge (空氣楔的薄膜干涉)
D. Multi-reflective Interference in Glass (玻璃片內多次反
射的干涉)
E. Diffraction of Light (光的繞射)
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一、雷射使用的基本安全規則
1. 雷射光很容易對視網膜造成永久性的傷害，切記絕對不可將
雷射光直接對著自己或他人的眼睛射照。
2. 雷射光經光滑表面反射得的雷射光也可能會對眼睛造成嚴重
的傷害，所以雷用使用操作時也要隨時留意，避免經雷射的
反射光照射到自己或他人的頭部。
3. 高功率的雷射光，縱使不是經光滑表面反射，而是經過一般
粗糙的表面散射後，仍極有可能對人的眼睛、甚或人體造成
不小的傷害。所以，高功率雷射更要嚴格遵守使用雷射的相
關安全規範。
4. 雷射的內部通常含有高壓電源裝置，特別是高功率雷射，故
未經允許不可隨意開啟儀器外殼，以免發生高壓觸電的危險。
5. 雷射電源線的插頭必須是含有地線的安全插頭，且必須插到
接有地線的電源插座上。以防萬一雷射內部漏電，電流可經
由接地線快速流通到地下，才不致傷害人體。
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二、雷射危險度分級與防範對策
Ref: http://www.phys.ncyu.edu.tw/~ygwu/lasar_safety.doc
1. 雷射危險度的分類
2. 雷射處理上的安全對策
3. 雷射對眼睛的傷害
4. 雷射光對皮膚的傷害
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I. Laser Safety Rulers
 Class 1 Lasers
1. A warning sign indicating the laser
classification should be placed in a visible
location on the laser.
 Class 2 Lasers
1. Do not stare at the laser or permit any
person to stare at the laser beam.
2. Do not point the laser at a person's eye.
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Class
3
Lasers
Never aim a laser beam at a person's eye.
1.
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 ofPhysicsNTHU
the laser beam
path.
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Class 4 Lasers
1. 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.
2. Confine indoor laser operation to a light-tight room with interlocked
entrances to assure that the laser cannot emit when a door is open.
3. 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.
4. Use remote firing and video monitoring or remote viewing through a laser
safety shield where feasible.
5. Use beam traverse and elevation stops on outdoor laser devices to assure
that the beam cannot intercept occupied areas or intercept aircraft.
6. 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.
7. Assure that the laser device has a key-switch master interlock to permit only
authorized personnel to operate the laser.
8. Install appropriate signs and labels on entrances, switches and anywhere an
unauthorized person might mistakenly activate the laser.
9. 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.
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10.Use dark, absorbing diffuse, fire-resistant targets and backstops
where
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feasible.
A. Refraction Index of Triangular Prism
(三稜鏡的折射率)
Object: To measure the refraction index of prism.
Principle: referred from http://hyperphysics.phyastr.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 thePhysicsNTHU
eye.
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Refraction of Light & Index of
Refraction
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Snell’s Law
Total Internal Reflection
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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 Ushaped 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
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prism parallel to the bottom of the prism.
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Experimental Procedures
5. 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.
6. 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, .
7. To measure the apex angle of the prism .
8. To determine the refraction index of the prism.
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B. Polarization of Light (光的偏振)
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