Mae gan groen arferol y gallu i amsugno golau i amddiffyn yr organau a'r meinweoedd yn y corff rhag difrod ysgafn. Mae cysylltiad agos rhwng gallu golau i fynd i mewn i feinwe ddynol â'i donfedd a strwythur meinwe croen. Generally, the shorter the wavelength, the shallower the penetration into the skin. The skin tissue absorbs light with obvious selectivity. For example, the keratinocytes in the stratum corneum can absorb a large amount of short-wave ultraviolet rays (wavelength is 180~280nm), and the spinous cells in the spinous layer and the melanocytes in the basal layer absorb long-wave ultraviolet rays (wavelength is 320 nm~400nm). The skin tissue absorbs different wavelengths of light differently, and most of the ultraviolet rays are absorbed by the epidermis. As the wavelength increases, the degree of penetration of light also changes. Infrared rays near the red light machine penetrate into the deepest layers of the skin, but are absorbed by the skin. The long-wave infrared (wavelength is 15~400μm) penetrates very poorly, and most of it is absorbed by the epidermis.
dadansoddwr croencan be used to detect deep skin pigmentation problems. Ydadansoddwr croen
