Gauthama, my NHS friend and photographic freak like me recently purchased Circular Polarizing Filter (CPL). We both were experimenting the effect CPL. We were amazed to see the difference. The basic purpose of CPL is to avoid and cut off unwanted and reflected light.. See the differences yourself.
In above two pictures first one is without CPL and second one is with CPL. You can see that unwanted reflection from floor is cut off. (Please bare with me, pics are under-exposed)
In above 2 samples, you can observe the same difference. The unwanted reflected light from spec is avoided in second snap. Another similar sample below..
I am planning to buy a CPL next week.. :D