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why rainbow halo around the sun (in chennai,TN,INDIA ON JULY 11th,2010)?

ANS:on july 11th,around the sun , a halo(circle) with rainbow formed.inside that halo it was dark.actually due to humidity present in the clouds at the edge of halo, each droplet in the clouds ,act as a prism and dispersion occurs.[DISPERSION means splitting up of seven colours (VIBGYOR) when white light(i.e.light from sun,mercury vapour lamp etc.,)falls on prism or any glass materials]so we can able to see rainbow around the halo.dark portion at the center is due to  wherever in the space when these seven colours are mixed in unequal proportions it becomes dark or ash in colour.due to radiation pressure(force of sun's hot radiation,which we can feel when you ride a bike in hot sun,you can experience hot air forcibly acting on your face etc., )the clouds are moved to a maximum distance on all sides equally and forms a circle or halo like.this halo is formed in space between earth and sun i.e.,far away from the sun.