What speed does light travel from the diode stack to the patient's skin?Light from the diode stack in a cosmetology laser (808 nm) is electromagnetic radiation, and its speed in vacuum and air is practically the same.Speed of light = 299,792,458 m/s
(approximately 300,000 km/s).What does this mean in practice?
- The distance from the diode stack to the patient's skin in the handpiece is usually 5–15 cm (inside the optical system: bars → lenses → sapphire window → skin contact).
- Time for light to travel this distance:
10 cm = 0.1 m → time = distance / speed = 0.1 / 299,792,458 ≈ 0.00000000033 seconds (0.33 nanoseconds).
In essence — instantaneously. The light reaches the patient's skin with virtually no delay.Why is this important to know?
- The entire effectiveness of hair removal depends not on the speed of light (it's always maximum), but on energy density (fluence), pulse duration, and cooling.
- Light doesn't "travel slowly" — it reaches the follicle in fractions of a nanosecond, while heating occurs in milliseconds (pulse duration 10–400 ms).
Fun fact: If you could see a laser pulse in slow motion, it would travel from the handpiece to the skin faster than you can blink (a blink is ~0.1–0.4 seconds).If you have calculations for a specific laser model — let me know!Romshi — Manufacturer of 808 nm Diode Stacks
Supplier of Laser Hair Removal Machines & Spare Parts www.romshi.com
