My iMac boots but the screen doesn't work My iMac boots(i can hear the jingle and the CD drive) but the screen doesn't work. Is the screen working and I closed the screen from software by some means. 

Model is  iMac12,1 (MC309XX/A) if I press some keys I can hear some sounds. 

I have reset the PRAM but it still does the same.

Does someone happen to know this situation?
I'd first try increasing the brightness. F2 or fn + F2 (depending on user preference settings for the function keys)is the hot key for brightness on the Apple Bluetooth Keyboard.

If that doesn't work, a trip to the genius bar or a repair center would be my next step.