Which bulb is which?

[g8rvet]

I just saw this forum and thought I would add one.  If it has been posted, sorry.

There is a room, with no windows.  Outside the room are three switches.  Inside the room are three plan light bulbs.  Each switch goes to one fixture.  You may do anything you want to the switches before you enter the room, but may not touch them after the door is opened.  How can you tell, exactly, without guessing, which switch goes to which bulb?

[Marc]

Turn one light on, and leave it on for some time...  Come back later, turn that light off, and turn on a different switch...

Immediately go inside and the light that is on goes to the switch that is on...  Touch the two remaining bulbs, and see which one is hot, and that is the first light that was already switched off...

I have not seen it here on this forum before...  Thanx for posting...

[g8rvet]