Measure the speed of light… with chocolate!
The speed of light is an important number that gets used in loads of equations. It’s the c in Einstein’s famous E=mc², for example!
But you don’t need to be the next Einstein to calculate this very important number. All you need is a slab of chocolate (at least 18cm by 8cm), a microwave, a piece of paper towel, a plate, a ruler and a few toothpicks.
Here’s how to do it:
- Check the frequency of your microwave. Most microwaves operate at 2,45 Gigahertz (GHz), but it’s best to check for the sign marked RF on your particular model.
- Remove the rotating plate and place a bowl over the rotating mechanism in the middle, so nothing will rotate when you turn the microwave on.
- Place a piece of paper towel on a plate.
- Remove the packaging from the chocolate and place the slab on the paper towel.
- Put the plate in the microwave, with the longest sides of the chocolate slab facing the front and back.
- Heat the chocolate until it barely starts to melt, stopping the microwave to check every once in a while. It should take 20 to 90 seconds, depending on the strength of your microwave.
- Once the chocolate has begun to melt, take it out of the microwave and feel the surface for a pattern of hot melted spots.
- Use toothpicks to mark the centre of each hot spot.
- Measure the distance between the toothpicks and double it to get the wavelength of light.
- Multiply the wavelength (in metres) by the frequency of your microwave to get the speed of light in metres per second.