LASERs

Question 1

The following features are true of Light Amplification by Stimulated Emission of Radiation (true or false):

It occurs spontaneously when a photon of light stimulates an atom

Answer 1

False. Spontaneous emission of radiation following photon stimulation of an atom is what defines fluorescence rather than LASER action.

Question 2

The following features are true of Light Amplification by Stimulated Emission of Radiation (true or false):

It occurs when electrons in a higher energy atomic orbit return to a lower energy orbit

Answer 2

True. Emission of radiation occurs due to electrons in high energy orbits falling to low energy orbits, whether this has occurred due to the action of other energised atoms (LASER activity) or whether by the action of an external energy source.

Question 3

The following features are true of Light Amplification by Stimulated Emission of Radiation (true or false):

It requires the interaction of identical neighbouring atoms with each other

Answer 3

True. Stimulation by energised atoms of identical neighbouring atoms is part of the process by which laser light is produced.

Question 4

The following features are true of Light Amplification by Stimulated Emission of Radiation (true or false):

Once the process has been initiated, there is no continuing requirement for an external energy source

Answer 4

False. The atoms in an energised state tend to spontaneously fall back into their ground state, so a continuing energy source is required.

Question 5

The following features are true of Light Amplification by Stimulated Emission of Radiation (true or false):

Amplification occurs by use of mirrors in a LASER device

Answer 5

True. As well as the energy source acting on the lasing medium, the use of mirrors allows continuous internal reflection of the stimulating light which ensures amplification of the process.

Question 6

Regarding the properties of LASER light (true or false):

The light is monochromatic, meaning a single colour

Answer 6

True. Mono- (single) -chromatic (colour).

Question 7

Regarding the properties of LASER light (true or false):

The light is coherent, meaning unidirectional

Answer 7

False. Coherent means the radiation waves are in phase.

Question 8

Regarding the properties of LASER light (true or false):

Light emitted as a result of phosphorescence is neither monochromatic nor coherent

Answer 8

True. These are two features which differentiate fluorescence from LASER activity.

Question 9

Regarding the properties of LASER light (true or false):

A reflected beam is less powerful than an incident beam

Answer 9

False. A reflected LASER beam is hardly attenuated at compared to the incident beam, and is one of the hazardous features of LASERs.

Question 10

Regarding the properties of LASER light (true or false):

Light from an argon LASER penetrates tissues to 2 mm

Answer 10

True. This is the penetration of an argon LASER (488-515 nm) used clinically.

Question 11

Regarding the different types of LASERs, their characteristic wavelengths and clinical uses (true or false):

LASER media exist as solids, liquids and gases

Answer 11

True. LASER media can exist in all these states.

Question 12

Regarding the different types of LASERs, their characteristic wavelengths and clinical uses (true or false):

A NAD:YAG LASER is a solid medium with a wavelength of 10 600 nm

Answer 12

False. A NAD:YAG LASER has a characteristic wavelength of 1064 nm.

Question 13

Regarding the different types of LASERs, their characteristic wavelengths and clinical uses (true or false):

An argon LASER is absorbed by haemoglobin and is used for coagulation

Answer 13

True. An argon LASER beam is blue-green in colour, and is absorbed by the complementary red colour of haemoglobin, and is therefore useful for coagulation of blood.

Question 14

Regarding the different types of LASERs, their characteristic wavelengths and clinical uses (true or false):

Dye LASERs are complex organic dyes in liquid solution, tuneable between 570 and 630 nm

Answer 14

True

Question 15

Regarding the different types of LASERs, their characteristic wavelengths and clinical uses (true or false):

Most LASERs in clinical use are in classes 1 to 3

Answer 15

False. Most LASERS in clinical use are class 4, with a higher output than those in classes 1 to 3, and are therefore more hazardous.

Question 16

Regarding power classifications of LASERs, their potential hazards, and safety precautions in a clinical environment (true or false):

High power class 4 LASERs are hazardous because they have a power output of more than 1000 mW

Answer 16

False. Class 4 LASERs are hazardous because of a power output of more than 500 mW.

Question 17

Regarding power classifications of LASERs, their potential hazards, and safety precautions in a clinical environment (true or false):

A class 4 LASER is hazardous to the eye and to the skin

Answer 17

True

Question 18

Regarding power classifications of LASERs, their potential hazards, and safety precautions in a clinical environment (true or false):

Goggles worn by LASER users protect the eyes against all laser wavelengths and are not necessary for the patient

Answer 18

False. Goggles used in the operating room should protect against a particular LASER emitting light of a specific wavelength. The patient’s eyes should be protected as well as those of all operating room staff.

Question 19

Regarding power classifications of LASERs, their potential hazards, and safety precautions in a clinical environment (true or false):

LASERs are a fire hazard only in an oxygen concentration of >35%

Answer 19

False. LASERs are a fire hazard, when used in the airway for example, in oxygen concentrations of more than 25%.

Question 20

Regarding power classifications of LASERs, their potential hazards, and safety precautions in a clinical environment (true or false):

Tube cuffs should be filled with saline rather than air when a LASER is used in the airway

Answer 20

True. Saline-filled tube cuffs are less of a fire hazard than air-filled cuffs.