How does sun cream block sunlight

An albino does not have the ability to generate melanin, so their hair is snow white, and their skin looks pale pink in colour because the blood corpuscles beneath its surface are the only chromophore they have. 

We have just seen that melanin is quite efficient at stopping UV light below about 370 nm. If the skin is damaged or the body cannot generate its own melanin - which is the case for an albino -then the UV will not be blocked. It is also common for young children and babies to have insufficient amounts of melanin in their skin to block the UV effectively. For this reason, babies should be protected from direct sunlight. 

Furthermore, following concerns over the way the ozone layer is being damaged by man-made chemicals, some UV-c now reaches the Earth s surface, particularly in Australasia and some parts of South America. People living in such places are not adequately protected against the harmful effects of the sun s rays by the melanin in their skin. 

There are now some health concerns concerning the safety of these compounds, since irradiation of Ti02 or ZnO causes the formation of radicals. 

The transmittance T of a sample is a quantitative measure of how much of the light entering a sample is absorbed. (Transmittance is also called optical transmittance, which means the same thing.) 

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