What is the practical effect of using a larger spot size on depth of penetration?

What is the practical effect of using a larger spot size on depth of penetration?

• A. Spot size does not affect penetration.
• B. Larger spot sizes increase energy density.
• C. Larger spot sizes enable deeper penetration and more uniform energy distribution.
• D. Larger spot sizes reduce treatment time.

Answer: (C)

Larger spot sizes change how the laser energy travels through the skin, allowing deeper penetration and more uniform heating. With a bigger spot, there’s less energy loss in superficial layers and less scattering, so more of the beam reaches deeper hair follicles. At the same time, a larger spot covers more area in a single pulse, distributing energy over a wider zone and reducing hotspots, which helps every follicle in the treated area receive a similar amount of energy. So the practical effect is deeper penetration and more uniform energy distribution. (Increasing spot size doesn’t automatically boost energy density per pulse; fluence depends on pulse energy and spot area, though size can still affect the overall tissue response.)

Larger spot sizes change how the laser energy travels through the skin, allowing deeper penetration and more uniform heating. With a bigger spot, there’s less energy loss in superficial layers and less scattering, so more of the beam reaches deeper hair follicles. At the same time, a larger spot covers more area in a single pulse, distributing energy over a wider zone and reducing hotspots, which helps every follicle in the treated area receive a similar amount of energy. So the practical effect is deeper penetration and more uniform energy distribution. (Increasing spot size doesn’t automatically boost energy density per pulse; fluence depends on pulse energy and spot area, though size can still affect the overall tissue response.)