i have an led tv , before some time when i was sitting in front of it [and it was off] i saw a colour spectrum on its screen formed by light coming through a near by window ? how this can happen ?

I suspect it is a thin film effect very similar to oil floating on water.

Probably not a led television but a LCD television with led backlighting.

 

All LCD displays have a polarizer film adhered to the glass screen. That is what is causing the reflection you perceive. The leds have nothing to do with it.

As Externet says, it'll be the TFT: http://en.wikipedia.org/wiki/Thin-film_transistor

Edited April 1, 201312 yr by theholykrael