almost all the replies will be vague
a vague question get a vague answer. You want a global answer to a derivative dependent value, that IS impossible.

some people over here do suggest to go to other websites etc..then why is this forum there for?
If the full and complete answer is at a website, then a reference is far better than a few words.

this is a techinical forum not an english literature board.so, i did'nt thought that people here will find some grammatical mistakes in my thread and even highlight the words then suggest on trivial things.
Nobody has critized you - or anyone else - for grammatical mistakes, I have chided you for laziness not taking the time to write your best english, which by the way is pretty good, instead of stupid SMS

erik wrote that he is not going to hire me..what was my original question(about led's) but now the topic is about hiring ..who asked u to hire me
You stated that tjis was an interview question, most interviews are about hiring.

and even now i dont know the right answer for the query put by me!
Sure you do, it was answered correctly way back, I believe by Andy, with "that depends".

Erik