Light Absorption Coefficient: How Light Behaves on the Skin

Whenever light comes into contact with a surface, it can do three things:

• Be absorbed: This is what we aim for in laser treatments.

• Be reflected: Light bouncing off the skin surface is energy lost. This is why patients must wear protective glasses.

• Be diffused: This leads to generalized heating but is not focused on the target.

Absorption is the key to successful treatment, as it converts light energy into heat, which can then destroy hair follicles. The substances in the skin that absorb light are called chromophores. The main chromophores in the skin are:

• Melanin (in hair and skin pigment)

• Hemoglobin (in blood vessels)

• Water (present in skin tissue)

Each chromophore absorbs light differently depending on the wavelength used. This allows for targeted treatments such as hair removal, pigmented lesion reduction, or vascular treatments​(Motus AY User Manual '22).

Learning Tip: Think of chromophores as "light magnets" that attract specific wavelengths of light to produce the desired effect, whether it’s hair removal or treating skin imperfections.