======Measuring the Speed of Light With a Microwave======


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**Alternative titles:** Microwave Marshmallow Speed of Light Experiment, Finding Wavelength of a Microwave 
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====Summary====                   
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====Procedure====  
  - Place mini-marshmallows in a microwave-safe dish in a single, even layer.  
  - Remove the rotating tray from your microwave so the dish does not move.  
  - Microwave the marshmallows for about 10 seconds (adjust if all or none melt).  
  - Remove the dish and observe where marshmallows melted compared to where they did not.  
  - Use a ruler to measure the distance between two adjacent melted spots (this represents half a wavelength).  
  - Find the frequency of your microwave (often listed on a sticker, usually around 2450 MHz).  
  - Use the equation: Speed of light = 2 × (distance between melted spots in cm) × (frequency in Hz).  
  - Compare your result to the accepted value of 3.00 × 10^8 m/s.



====Links==== 
Measuring the Speed of Light with Marshmallows - Wise Wonders:
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📄 Measure the Speed of Light Using Your Microwave - The Wonders of Physics: [[https://wonders.physics.wisc.edu/measure-the-speed-of-light/]]\\

====Variations====
  * Try using chocolate chips instead of marshmallows.  
  * Test different microwaves to see if results vary.  
  * Use larger dishes to get more melted spots and more accurate measurements.



====Safety Precautions====
  * Always use oven mitts when handling hot dishes.  
  * Do not overheat marshmallows to avoid burns or fire.  
  * Ask an adult for help when removing the rotating tray.




====Questions to Consider====
  * Why do the marshmallows only melt in certain spots? (Because those spots are at the peaks of the standing wave, where the microwave energy is strongest.)  
  * Why is the measured distance only half a wavelength? (Because the distance between adjacent peaks is half the wave’s full cycle.)  
  * How close did your calculation come to the actual speed of light? What might cause differences? (Errors may come from uneven heating, inaccurate measurement, or microwave timing.)  
  * What does this experiment show about the nature of light and microwaves? (That light, like microwaves, behaves as a wave with measurable wavelength and frequency.)