Everyone knows what a sunscreen is. It protects skin from the sun's radiation, particularly UV.

 

UV radiation can be broadly classified into 3:

 

UV-A:

 

1.Longest wavelength.

2.320-400nm.

3.Not absorbed by ozone.

4.Penetrate the top layer of skin.

5.Cause tanning, ageing, wrinkling, cancer of skin 

 

UV-B:

 

1.Medium wavelength

2.280-320nm.

3.Considerably absorbed by ozone.

4.Penetrate less deeply than UVA.

5.Cause delayed tanning, burning, ageing of skin etc.

 

UV-C:

1.Shortest wavelength.

2.100-280nm.

3.Completely absorbed by ozone.

4.Extremely hazardous to skin.(Shortest wavelength, so highest energy, max damage)

 

UV radiations can change the structure of cell and may result in mutation.

 

Sunscreens contain Aromatic compounds that absorb energy in UV region of electromagnetic spectrum. Now, what does it do after absorbing UV? Absorption of UV radiation promotes the electrons to higher energy levels after which the energy is dissipated through vibration of molecules. Or, we can say, UV is converted to IR in the form of heat.

 

The common aromatic compounds present in sunscreen are: para-aminobenzoic acid(PABA), 3-phenylpropenoic acid(cinnamic acid), benzophenone, o-hydroxybenzoic acid(salicylic acid).