BLOCK 6: NON-IONIZING RADIATION - Units 7, 8, 9, & 10: Lasers (complete)

Question 1

Laser radiation is optical radiation that propagates in the form of a beam that maintains special properties. We rely on the LASER acronym to help us understand these special properties of laser radiation:

Answer 1

Light Amplification by Stimulated Emission of Radiation

Question 2

What are the 3 main components of a laser?

Answer 2

–> POWER PUMPING STATION
–> ACTIVE MEDIUM
–> OPTICAL CAVITY

Question 3

The source of energy that creates excitation of the laser medium (active medium).

Answer 3

POWER PUMPING STATION

Question 4

The source of photon energy found in the center of the laser.

Answer 4

ACTIVE MEDIUM

In this picture, the He-Ne mixture is the active medium in gas form. There are three different types of active media that laser systems may use: solid state, gas/dye, and semiconductor.

Question 5

Acts like a resonant feedback system that focuses and amplifies the photon energy into a coherent and collimated state to create the laser beam.

Answer 5

OPTICAL CAVITY

An optical cavity contains the active medium and consists of a fully reflecting mirror at one end and a partially reflecting mirror at the other. An optical cavity is required to provide the amplification desired in the laser and to select the photons which are traveling in the desired direction.

Question 6

A light beam is said to be _______________ when there is a lack of cohesion, connection, or harmony.

Answer 6

INCOHERENT

Flashlights, lamps, and light bulbs are considered incoherent.

Question 7

A measure of the degree of phase correlation that exists in the radiation field of a light source at different locations and different times. Waves of laser light are tightly in phase or in step with one another.

Answer 7

COHERENCE/COHERENT

Question 8

The ability of the laser to minimize beam divergence (spread) over a given distance. Lasers have very low divergence. This can be best seen by comparing a laser with a flashlight.

Answer 8

COLLIMATION

Question 9

Delivers its energy in a form of a single pulse or a train of pulses.

Answer 9

PULSED EMITTING LASER

Question 10

TRUE OR FALSE:

Different types of lasers may fall into different categories within the EM spectrum.

Answer 10

TRUE

There are infrared lasers from 1400 to 700 nm, visible lasers in all colors from 700 to 400 nm, and ultraviolet lasers from 400 to 200 nm. (Fig. 21). The wavelength may determine certain characteristics of a laser but does not necessarily indicate the health risk severity of a laser.

Question 11

Generally, lasers in the UV region induce _______________ reactions; lasers in the infrared region induce _______________ effects.

Answer 11

Lasers in the UV region tend to induce PHOTOCHEMICAL reactions, while laser in the IR region induce THERMAL effects.

Question 12

The various structures of the eye and/or skin transmit, reflect, and absorb optical energy. Structures that transmit light are not damaged; therefore, energy must be _______________ to cause damage.

Answer 12

ABSORBED

Question 13

The _____ and _____ are the two critical organs susceptible to damage from lasers.

Answer 13

EYES and SKIN

The type of injury, threshold for injury, and damage mechanisms vary significantly with the laser’s wavelength.

Question 14

What areas of the eye are the most commonly damaged by lasers?

Answer 14

RETINA, CORNEA, and LENS

Question 15

____________________ is the most common cause of laser-induced skin damage.

Answer 15

THERMAL (BURN) INJURY

The thermal damage is generally associated with lasers that are operating at exposure times greater than 10 microseconds and in the wavelength region from the near ultraviolet to the far infrared.

Question 16

The _______________ is susceptible to injury by laser systems and is considered the primary organ of concern.

Answer 16

HUMAN EYE

The lens of the eye focuses the beam to a very small spot on the retina, the light sensitive layer at the back of the eye. The resulting high intensity may lead to a local burn, which causes degradation of vision.

Question 17

A layered, light-sensitive membrane in the inner eyeball connected to the brain by the optic nerve, acts as a screen on which to project images, like a projection screen television, and is considered the most sensitive structure of the eye.

Answer 17

RETINA

It uses rods and cones to detect light and color to create the imaging property of the eye. The retina is most susceptible to visible light and near infrared radiation within the 350 to 1400 nm range of the EMF spectrum.

Question 18

Provides the most acute vision and color perception for your eyesight.

Answer 18

FOVEA

Question 19

Common injuries to the _______________ are thermal coagulation, edema, and hemorrhage. Additional injuries include not allowing passage of light; significant loss of vision; and blind spots (scotoma).

Answer 19

RETINA

Repeated retinal burns from lasers may also lead to blindness.

Question 20

The transparent layer on the front of the eye and is susceptible to lasers producing UV within the 200 to 350 nm range and mid to far infrared radiation in the 1400 nm to 1 mm range.

Answer 20

CORNEA

The most common health complications to the cornea from lasers are photokeratitis, corneal discoloration, and blurred or optical obstructions.

Question 21

A transparent body behind the iris (colored part of the eye) that works with the cornea to focus light on the retina.

Answer 21

LENS

The focusing effect of the lens, along with the cornea of the eye, intensifies the laser beam which can be amplified by a factor of 100,000 times to the retina. This makes it susceptible to the formation of cataracts (cloudiness) when exposed to near UV and middle IR radiation and, thus, more susceptible to laser damage.

Question 22

The black-appearing center of the eye that changes size in response to light, and is also subject to damage as it may dilate, allowing 100 times more light into the eye.

Answer 22

PUPIL

Dark rooms or night exposures to lasers are more hazardous due to dilation of the .

Question 23

The secondary organ of concern is skin. Laser radiation can damage living tissue by which three basic mechanisms?

Answer 23

PHOTOMECHANICAL effects from pulsed lasers,
THERMAL effects from all lasers, or
PHOTOCHEMICAL effects from lasers in the UV range

Question 24

_______________ action, also known as acoustical effects, causes localized vaporization though brief pulses of light. These pulses can create a mechanical shockwave that spreads through the tissue. Shockwaves can cause tearing of tissue and can cause internal or external hemorrhaging (bleeding).

Answer 24

PHOTOMECHANICAL

Question 25

_______________ occur when the body’s ability to dissipate absorbed heat via evaporative and convective processes is overwhelmed and its temperature rises to damaging levels.

Answer 25

THERMAL BURNS

Thermal effects occur through energy absorption/heat buildup commonly referred to as the “cooking effect.” Short-term effects from lasers can cause instantaneous tissue damage; whereas, longterm effects cause heat buildup from sustained exposures.

Question 26

_______________ effects result from exposure to wavelengths less than 550 nm (blue-green through ultraviolet). These wavelengths can disrupt cell chemistry and may damage DNA, potentially causing mutagenic and cytotoxic effects within the cell.

Answer 26

PHOTOCHEMICAL

Question 27

TRUE OR FALSE:

A comprehensive laser inventory is required by federal law wherever lasers are used.

Answer 27

FALSE

A laser inventory is not “required” by regulation, however, it is important to know where and what radiation sources exist at a work center.

Question 28

A painful, temporary eye condition caused by exposure to ultraviolet rays.

Answer 28

PHOTOKERATITIS

Question 29

What are the primary ways of identifying radiation sources in the workplace?

Answer 29

–> INTELLIGENCE (example: documentation)
–> OBSERVATION (from routine/non-routine shop visits)
–> INTERVIEWS (with shop supervisors/workers)
–> SURVEYS

Question 30

In an _______________ setting you may find lasers for various operations such as laser cutting, laser micro-drilling, and carpentry alignment.

Answer 30

INDUSTRIAL

Question 31

In a _______________ facility you may find lasers used for LASIK eye surgery, dental procedures, skin resurfacing, and endootoprobe procedures (ear surgery).

Answer 31

MEDICAL

Question 32

Another application for lasers in the Air Force is in _______________ ; lasers are used in many ways to conduct scientific and materials research.

Answer 32

RESEARCH

Question 33

____________________ operations requiring laser systems are commonly directed at advancing weapons systems. Common uses for lasers in the Air Force are tactical high-energy lasers, airborne lasers, precision-guided munitions, directed energy weapons, and targeting and navigation.

Answer 33

MILITARY-SPECIFIC

Question 34

The increase in beam diameter (spread) as the distance increases from the laser

Answer 34

DIVERENCE

Question 35

The highest power per unit area is from the _______________ of the laser.

Answer 35

APERTURE (or opening)

Question 36

The primary organ of concern is the __________ due to the viewing of the laser beam.

Answer 36

EYES

Depending on the intensity and duration from viewing the beam, lasers can cause irreversible damage to one’s eye.

Question 37

The most dangerous way an eye can be affected by a laser is through direct or _______________ viewing.

Answer 37

INTRABEAM VIEWING

This is where the laser beam exits the laser and has the ability to enter directly into the eye.

Question 38

This is where the laser beam reflects off a mirror-like surface and maintains its characteristics (especially collimation where the light rays spread minimally). The mirror-like surface can be a mirror, glass, water, or even a wall with a very smooth surface.

Answer 38

SPECULAR REFLECTION

Question 39

Reflection off a non-reflective or uneven surface that changes the geometry/properties of the beam, causing the laser beam to spread, thus becoming less collimated and less hazardous.

Answer 39

DIFFUSE REFLECTION

Question 40

Any laser system containing a laser that cannot emit laser radiation at levels that are known to cause eye or skin injury during normal operation.

Answer 40

CLASS 1 LASER

Lasers can be Class 1 because they are very low power or because the beam is fully enclosed. A laser normally classified as a Class 3 or 4 may be classified as a Class 1 if it is embedded into the components of another system, such as a fully enclosed laser engraver. If, however, the component in which the laser is embedded is opened for maintenance, then the maintenance personnel will be subject to the higher-class controls.

Question 41

Low-power visible lasers. Under normal operation, they are considered not strong enough to damage a person’s eyes because a person will normally blink and look away from the laser if it enters the eyes.

Answer 41

CLASS 2 LASER

However, these lasers may not be safe for a person who deliberately overcomes the natural aversion response to a very bright light and stares into the laser beam for longer than 0.25 second.

Question 42

A sub-classification of the Class 1 laser, where it is considered incapable of
producing hazardous exposure unless viewed with collecting optics, such as binoculars.

Answer 42

CLASS 1M LASER

Question 43

A subclass of Class 2, they are intermediate-power visible lasers, but are potentially hazardous in less than 0.25 seconds if viewed with collecting optics.

Answer 43

CLASS 2M LASER

Question 44

High-power lasers that are hazardous to view under any condition (i.e. direct beam or diffusely scattered) and are a potential skin and fire hazard.

Answer 44

CLASS 4 LASER

Question 45

Lasers that are potentially hazardous under any viewing conditions and may present skin hazards if focused and stable.

Answer 45

CLASS 3B LASER

Question 46

Intermediate-powered lasers and may be hazardous under direct and specular reflection viewing and may be hazardous with diffuse reflection if the eye is appropriately focused and stable.

Answer 46

CLASS 3R LASER

Question 47

The maximum level of laser radiation to which personnel may be exposed without adverse biological effects.

Answer 47

MAXIMUM PERMISSABLE EXPOSURE (MPE)

Question 48

The MPE is dependent on the wavelength and exposure duration of the laser system and is
expressed in _______________.

Answer 48

JOULES PER SQUARE CENTIMETER (J/CM^2)

Question 49

The distance along the laser beam, beyond which the exposure is not expected to exceed the appropriate MPE.

Answer 49

NOMINA OCULAR HAZARD DISTANCE (NOHD)

Question 50

The area within a laser workplace in which the exposure from direct beam, specular, and diffuse reflection could exceed the MPE

Answer 50

NOMINAL HAZARD ZONE

Question 51

Used to totally enclose the entire length of the beam and are considered the most effective engineering control for laser hazards.

Answer 51

BEAM ENCLOSURE

By using a beam enclosure, you may eliminate the need for other safety precautions, because the beam is inaccessible to the worker at risk. In most operations, this control is not feasible due to Air Force mission requirements.

Question 52

A physical barrier sufficient to contain the beam and laser radiation from exiting the laser system, except at the beam aperture.

Answer 52

PROTECTIVE HOUSING

Protective housings or enclosures must have an interlock system, which is activated when the protective housing is opened during operation and maintenance.

Question 53

Control in which the laser is maintained at a height level other than the normal position of the eye of a person in standing or seated position and never look into the beam.

Answer 53

LASER BEAM HEIGHT

Question 54

Usually work in tandem with a protective housing; protective housings must be _______________ so that the laser cannot operate when the housing is opened or removed.

Answer 54

INTERLOCKED / INTERLOCKING

Question 55

All Class 3B or 4 lasers and laser systems require a ____________________. The switch can be operated by a key or computer code. When disabled (key or code removed), the laser cannot be operated. Only authorized system operators are to be permitted access to the key or code.

Answer 55

MASTER SWITCH CONTROL

Question 56

Can be used where the user may operate the laser system remotely rather than directly near laser sources.

Answer 56

REMOTE OPERATION

Question 57

Inside the laser control area; an alarm (for example, an audible sound
such as a bell or chime), a warning light (visible through protective eye wear), or a verbal
“countdown” command can be used during activation or startup.

Answer 57

WARNING SYSTEMS

Question 58

Written procedures that should be established for operation, alignment, and
maintenance of laser systems.

Answer 58

STANDARD OPERATING PROCEDURES (SOP)

Question 59

Personnel working with/near lasers should be properly _______________ and educated to understand the risks and hazards associated with laser radiation. Understanding that beams do not have to be viewed directly to cause damage is very important to worker protection.

Answer 59

TRAINED / TRAINING

Question 60

Only those individuals who are trained and aware of proper safety practices are allowed in the environment where the laser hazard exists.

Answer 60

ACCESS LIMITS

Question 61

Verbiage is based on the laser classification; posted state precautionary or protective instructions and describe the type of laser, emitted wavelength, maximum output, and pulse duration along with the class of the laser.

Answer 61

SIGNS

Question 62

When selecting PPE to control laser radiation hazards, we are primarily concerned with protecting the __________ and __________.

Answer 62

SKIN and EYES

Question 63

Skin protection can best be achieved through _______________ controls which terminate or enclose the laser radiation.

Answer 63

ENGINEERING

Question 64

All protective eyewear must be clearly labeled with the _______________ and _______________.

Answer 64

OPTICAL DENSITY and WAVELENGTH