Puzzle 38 - Light

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 Here is an easy logical puzzle. And many of you already know the solution.

There is a closet and a light bulb inside this closet. You can not see whether the bulb is on or off from outside. There are three switches outside the closet one of which controls the light bulb. You can not see these switches from the closet.

How do you find out which switch controls the bulb with a single try?

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