You are standing outside a closed door. On the other side of the door is a room that has three light bulbs in it. The room is completely sealed off from the outside. It has no windows and nothing can get in or out except through the door. On the outside of the room there are three light switches that control each of the respective light bulbs on the other side of the door.
Your assignment is to determine which light switch controls which light bulb. You are allowed to enter the room only once, and once you come out, you must be able to state with 100% certainty which light switch controls which light bulb.
Turn one light switch on, wait a few minutes, then turn it off and turn another light switch on. Go into the room and feel the light bulbs. The one that's still warm is connected to the switch that you first turned on, the one that is on was the second switch you turned on, and the last bulb is controlled by the switch that you didn't touch.
To determine which light switch controls which light bulb, you can follow these steps:
1. Start by turning on the first switch and leaving it on for a few minutes.
2. After a few minutes, turn off the first switch and turn on the second switch.
3. Now, enter the room and observe the light bulbs.
- If one light bulb is on, that means it is controlled by the first switch.
- If one light bulb is off but warm to the touch, that means it is controlled by the second switch.
- If one light bulb is off and cool to the touch, that means it is controlled by the third switch.
Here's the explanation behind this approach:
Initially, all the light bulbs are off. When you turn on the first switch, one of two things can happen:
1. If the first switch controls the bulb that lights up, then you will find the bulb on. In this case, it means the first switch controls the first light bulb, and you can move to step 2.
If the first switch does not control the bulb that lights up, then either the second or third switch controls the first bulb. Proceed to step 2.
Next, you turn off the first switch and turn on the second switch. Here's what can happen:
2a. If the second switch controls the bulb that is still on and warm to the touch, then the second switch controls the second bulb.
2b. If the second switch controls the bulb that is off and cool to the touch, then the third switch controls the second bulb.
Lastly, the remaining switch that has not been used yet must control the third light bulb.
To summarize, by using a process of elimination and observing the behavior of the light bulbs after manipulating the switches, you can determine with certainty which switch controls each light bulb.