Laser Physics & Safety Principles Flashcards
7 cards from real CLT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Laser Physics & Safety Principles flashcards as text
In a pulsed laser system, 'duty cycle' refers to:
Answer: The ratio of pulse-on time to the total period (on + off time)
Duty cycle = pulse duration × repetition rate, expressed as a percentage representing the fraction of total time the laser is actively emitting.
The laser beam property that describes highly parallel photon travel with minimal angular spread is:
Answer: Collimation
Collimation is the near-parallel directionality of laser beams, enabling tight focusing and maintaining intensity over long distances unlike conventional light sources.
The 'optical window' of tissue (approximately 600–1100 nm) is clinically significant because:
Answer: Both water and hemoglobin absorption are relatively low, enabling deeper photon penetration
In the 600–1100 nm optical window, the major tissue chromophores (water, hemoglobin) have lower absorption coefficients, allowing photons to penetrate several centimeters into tissue.
What distinguishes low-level laser therapy (LLLT) from ablative or surgical lasers in terms of tissue effects?
Answer: LLLT operates at sub-thermal power levels that stimulate biological processes without causing tissue destruction
LLLT uses power levels insufficient to heat tissue above physiological temperature, instead stimulating photobiomodulation pathways without ablation or coagulation.
The Er:YAG laser (2,940 nm) is particularly effective for skin resurfacing primarily because:
Answer: Its wavelength coincides with the peak water absorption coefficient, enabling precise superficial ablation
At 2,940 nm, the Er:YAG wavelength matches the peak absorption of water in tissue, allowing highly efficient, precise ablation with minimal residual thermal damage.
Why must laser safety eyewear be worn throughout the entire NHZ and not only when looking toward the beam?
Answer: Diffusely scattered laser light can still enter the eye and be focused by the lens onto the retina
Scattered laser light can enter the eye from oblique angles and still be focused to a damaging irradiance on the retina by the eye's optical system.
In photobiomodulation, the primary intracellular target believed to mediate therapeutic effects is:
Answer: Cytochrome c oxidase in the mitochondrial respiratory chain, leading to increased ATP production
Cytochrome c oxidase absorbs red and near-infrared photons, enhancing mitochondrial electron transport and ATP synthesis, which underpins photobiomodulation's cellular effects.