Bheja fry question

 Recently I came across this question on web radio.

Question

You are alone in a room.

Room has a door.

On the wall of the room, there are 3 switches.

These switches are connected to 3 bulbs which are at the other side of wall.

You have to tell which switch is for which bulb?

You can go out of the room to check whether the bulbs are glowing, only only once.

How do you do it  ???

Listening to the question, I was in the deep thought. 

It would be better if there are only 2 switches and 2 bulbs. I would have solved this puzzle in a second. !!

Now how to proceed ?

First switch on two switches.

Let them like that for 5 minutes.

Now out of 2 switches, switch off one switch.

Now remember there is already an untouched switch along with the switch we just have switched off.

Now open the door.

On the other side of wall, one bulb would be glowing as we have kept one switch ON. 

So this is the switch for the glowing bulb. 

Now there are 2 bulbs which are OFF. 

Out of them, one bulb would be hot compared to other bulb as it was ON for 5 minutes. 

Hence we can conclude the remaining switch we had used earlier out of 2 switches , is for the hot bulb. 

Now the left out bulb is connected to remaining untouched switch. 

PROBLEM SOLVED  !!!