Which parameter change decreases the wavelength in laser settings?

• A. Increasing spot size (mm)
• B. Decreasing energy (J/cm2)
• C. Decreasing wavelength (nm)
• D. Increasing repetition rate (Hz)

Answer: (C)

Wavelength is a property of the laser light set by the laser source itself—the medium, the cavity design, and any wavelength-converting steps used. Changing how large the spot is or how much energy per area you deliver, or how often pulses occur, affects fluence, treatment speed, and interaction with the target, but not the actual wavelength of the light. So the only way to decrease the wavelength is to use a shorter-wavelength emission from the source (or apply a wavelength-conversion method to produce a shorter wavelength). The other adjustments influence energy delivery and timing, not the light’s wavelength.