Page 199 - Blog Posts v1

E2 - Where do photons go in the skin?
When photons (light) enter the skin they can undergo only two processes – absorption or scattering.
Once a photon is absorbed, its energy is ‘gained’ by the absorbing site. This may be a melanosome in the epidermal basal layer (see figure 1 – ‘Epidermal absorption’). This absorption will transfer the photon’s energy into the melanin and raise its temperature (by a very small amount!)
Figure 1 – Absorption and scattering in the skin
More likely, the photons will scatter throughout the dermis as they ‘bounce’ off many atoms (this can be anywhere between 1 and several million atoms!!). This is because the likelihood of being absorbed in relatively low in most parts of the dermis, until the photons encounter something which ‘wants’ to absorb them strongly – like blood or melanin or another chromophore.
At some point a photon may be absorbed in the dermis (see figure 1 – ‘Dermal absorption’).
If it not absorbed by an atom in the dermis, it may continue its ‘random walk’ through the dermis until it reaches the deeper, fatty layer – where it may be absorbed by an atom there.
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