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28 Cards in this Set
- Front
- Back
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Thin lens
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Image distance = Focal distance
i=f |
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Magnification
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m=i/o=fpos/fneg
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collimated beam
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when focal points overlap
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eye damage - cornea
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ultraviolet
far infrared |
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eye damage - retina
to some degree cornea, lens and eye fluids |
visible
near infrared |
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a. Point source
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a source of light that radiates energy in all directions
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b. Extended source
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illuminates a point from many different directions
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4 processes that account for all light energy striking a surface
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a. Reflection
b. Transmitted c. Scattered d. Absorbed |
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a. Specular reflection
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reflected light that occurs at smooth surfaces and does not change the character of the beam itself.
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b. Diffuse reflection
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reflected light that occurs at rough reflecting surfaces and reflects light randomly and in all directions
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c. Fresnel reflection
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partial reflections of light from smooth surfaces of transparent material. First (diverging) and second (converging) surface reflections considerably reduce the magnitude of the light though second surface reflections can present an eye hazard
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Interbeam viewing
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direct viewing of a laser beam. The coherent directional laser beam enters the iris of the eye and is focused on the retina and has a much higher irradiance than the partial beam of a diffuse reflection
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ANSI Z136.1
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a. Defines maximum permissible exposure levels for various parts of the body
b. Presents a classification scheme for lasers, according to their level of hazard c. Presents safety measures, practices and procedures to be observed with lasers of each classification |
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a. Class 1
b. Class 2 |
a. lasers that cannot emit damaging levels of laser power because of low power or they are fully enclosed
b. lasers operating in the visible portion of the spectrum (400 nM to 700 nM) and for which protection is provided by the normal aversion response |
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c. Class 3
d. Class 4 |
c. medium power lasers which would be dangerous if viewed directly or the specular reflection were to be viewed. Viewing diffuse reflections would not be hazardous
d. high power lasers including continuous visible lasers with power output above 0.5 watts. They are hazardous for viewing a direct beam or specular reflections and may be for diffuse reflections as well. They may also be a hazard for skin burns and associated hazards such as fire |
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a. Frequency
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the number of cycles per second of a repeating wave
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b. Wavelength
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the distance over which a wave repeats itself
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Period Phase
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when all light waves are in step
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d. Amplitude Polarization
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describes the orientation of the electric field in space
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e. Hertz
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frequency in cycles per second
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4. Index of Refraction
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a ratio of the velocity of light in a vacuum to its velocity in a given material
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brewsters angle
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8. The angle at which all the parallel component of a wave and 85% of the perpendicular component are transmitted thru a medium.
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Temporal coherence
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concerned with the phase correlation of waves at a given point in space at two different instants of time.
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Spatial coherence
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the phase correlation of two different points across a wave front at a given instant of time
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antireflection coatings
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a. Reflection occurs at each surface of the coating. The two reflected waves are 180 degrees out of phase and cancel through destructive interference. No energy appears in the reflected beam and all the light is transmitted
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low to high (n)
high to low (n) |
180 phase change
no phase change |
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high reflectivity coatings
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using multiple layers at quarter wave thickness all the reflected waves are in phase and produce constructive interference increasing the reflectivity of the mirror.
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polarization orientation
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unpolarized
plane polarized horizontally polarized vertically polarized |
