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CIH Non-Ionizing Radiation Questions and Answers Graded A+
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CIH Non-Ionizing Radiation
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CIH Non-Ionizing RadiationLASER - answer Light Amplification by Stimulated Emission of Radiation
Two types of lasers - answer Continuous wave and pulsed. Each has different types of
health risks.
Continuous wave (cw) - answer Light is emitted continuously. t is greater than or equal
to .25 seconds, which is the human blink reflex.
Pulsed - answer Light is emitted in pulses. t is less than .25 seconds.
Laser safety quantities - answer Irradiance, which is the dose rate and Radiant
Exposure, which is the dose.
Irradiance (dose rate) - answer Is power divided by area and is measured in watts per
centimeter squared (W/cm2). It is used for continuous wave lasers. When light goes
through lens it focuses it and it gets concentrated and causes a decrease in the area we
are concentrating the power to. 1 watt is equal to 1 joule per second.
Radiant exposure (dose) - answer Is energy divided by area (j/cm2). It is used for
pulsed lasers.
Irradiance calculation - answerNot on equation sheet, must memorize.
E=irradiance, P=power (W), A=Area (cm2)
E=P/Area=4P/3.14(d2)
Divergence - answerLaser beams are directional and do not diverge much. Divergence
measure how much the beam spreads. a is equal to emergent beam diameter and is
measured in millimeters.
Angular measurement - answerradians is equal to arc length (S) divided by radius (R).
1 radian is equal to 57.3 degrees
Target organs for laser damage - answerEyes are the most vulnerable and can receive
thermal and photoreceptor damage. Skin can also receive thermal and photochemical
damage.
, Types of laser exposure - answerDirect through looking at beam or specular reflection.
Indirect through diffuse reflection or scattered beam (bounces off surfaces). Short
wavelength lasers (less than 220 nanometers) can create ozone.
Cornea Hazard Range - answerNear UV (315 to 390 nanometers) are absorbed in
cornea and lens of eye. Penetration increases as wavelength increases.
Human visible UV range - answer400 to 700 nanometers. The closer UV light is to this
range, the more penetration will occur.
Retinal Hazard Range - answer400 to 1400 nanometers is the hazard range. The retina
is at the back of the eyes so this is deeper penetration. IR-A is 700 to 1400 nanometers.
Eye Surfaces - answerAbsorbed by water in the eye surfaces. Mid and far IR (1400
nanometers to 1 millimeter). Mid UV (180 nanometers to 315 nanometers).
Laser Exposure limits - answerTLV changes based on the wavelength of the laser.
Pulsed lasers have a TLV in radiant exposure (J/cm2). Continuous wave lasers have a
TLV in irradiance (W/cm2), which is also Joules divided by centimeters squared
multiplied by seconds. (j/cm2 x sec).
ANSI Z136 - answerLasers Classification standard
Class 1 laser - answerSafe under all conditions of normal use.
Class 1M laser - answerSafe for all conditions unless passed through magnifying optics.
Class 2 laser - answerSafe because the blink reflex limits exposure to less than .25
seconds.
Class 2M laser - answerSafe if not viewed through magnifying optics.
Class 3R laser - answerRestricted beam viewing
Class 3B laser - answerDiffuse exposure safe, but direct viewing hazardous
Class 4 laser - answerSkin and permanent eye injury possible
General Operational Parameters - answerWavelength, exposure duration, radiant
power, beam divergence, emergent beam diameter.
Pulsed Laser Parameters - answerAll of the general operational parameters plus energy
per pulse, pulse repetition frequency, pulse width (how long is pulse penetrating),
average power.
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