what is meant by photo-oxidation.How does accessory pigments protect chlorophyll a from photo oxidation?

Photo oxidation is the destruction of light absorbing pigments like chlorophyll a due to excessive exposure to light energy and oxygen.

The pigments other than Chlorophyll a present in chloroplast are called accessory pigments. The accessory pigments like xanthophylls desiccate the excess photon energy and protect the chlorophyll a from photo oxidation.