Microwaving a Lightbulb

In an effort to help students visualize the energy transmitted by microwave ovens, it is possible to use this microwave energy to make a lightbulb fluoresce.

This demonstration is fairly straightforward but has some important safety considerations that I will outline below 

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Set Up

Preparing a Lightbulb

• There are probably several styles of lightbulb that works for this demonstration but I am partial to a 12" tube like this one on Amazon. This is the same style of bulb that I use for my plasma ball magic so it is a nice chance to double dip on materials :)​
  
• You will notice in the picture and video below that the ends of this lightbulb have been taped over with electrical tape. This prevents plasma from arcing between the pointy metal contacts on the light bulb. I usually keep taping until no more metal is visible just in case.

Preparing the Microwave

• The microwave that I use for this and other microwave demonstrations has been retired from any food applications and is now entirely devoted to science. I would recommend against doing this in a microwave that you still plan on using for food.
• Since the lightbulb doesn't have much mass to absorb the microwave energy, it is important to include a couple of beakers of water.
• With the size of my lightbulb and beakers, I have disabled the turntable by removing the "wheels" from below the glass plate. Depending on the size of the bulb/microwave this may not be necessary though.
• Even with the added mass of the water beakers, I still only run this microwave in bursts of 10 seconds or so. Even in this short duration of time, it is sometimes possible to feel the lightbulb heating up and you don't want to run this risk of the bulb exploding.

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Running the Demonstration

Once you have ensured that everything is set up correctly, you just need to run the microwave for 10 seconds or so and watch the light show. I still remember the first time that I saw this and how shocking it was to see the lightbulb lighting up all on its own with the contacts taped off.

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