July 13th, 2013
Measure the speed of light with your microwave!
Anime Relations: Steins;Gate
Absurdity? Science.
The tools you will need: a microwave, a ruler, a calculator, and a bar of chocolate (yes, chocolate).
Here is a briefer on all the physics you need going into this. If you already know what a standing wave is, and how to calculate wavelength, skip to after the pink fluffy teddy bear.
1) Microwaves are part of the electromagnetic spectrum. This spectrum includes UV rays, visible light, and X rays, and can most easily be described as a bunch of things that act like visible light, with the exception that we can't see them. And like visible light, microwaves travel at speed of light.
2) Microwave ovens emit microwaves in a special configuration, called a standing wave. A standing wave is a wave that stands so perfectly fits its container that it looks like it's standing still. You have probably created standing waves as children playing with jump ropes. If you lift the rope and push at the right moment, the jump rope will have one place that goes up and down - moving into peaks and valleys, while staying still at the two ends. If you put a little more effort into it, you can make the jump rope have two places that form peaks and valleys, and three points where it appears to be 'standing'. Here is Walter Lewin demonstrating the principle.
This s-like curve is one wave, and the length of it is one wavelength.
This principle of standing waves also applies to microwaves in the oven. The points that don't form peaks and valleys are points where no oscillation occurs. This is why the microwave tray rotates: it moves the food to ensure that every part of your food is exposed to the places of highest oscillation, resulting in a more evenly heated product.
3) The number of waves that pass by a certain point per second is called the frequency of the waves. Frequency, wavelength, and the speed of waves have the following established relation:
(Frequency) x (Wavelength) = Speed
With this, you are ready to do science!
It is time.
========
Place the chocolate bar (without the plastic!) into the microwave whose rotating tray has been removed. I recommend placing the chocolate on a microwavable plate for convenience. Heat the bar until you can make out at least 2 soft spots, which are the bubbles from heating. Since the tray isn't moving, the melting will not be even. Certain points will begin to bubble while the rest of the bar will be unharmed. The ideal chocolate bar for this experiment will have a smooth surface. Once you see these soft spots, stop the heating. It should look something like this:
Use the ruler to measure the distance between those two spots (ideally measured from their centers). This is half the wavelength of the microwaves emitted by your oven. Soft spots in red:
Double that distance, and you'll naturally have the required wavelength. Now convert this number to meters. A simple Google search of "x inches to m" should suffice.
Next you need the frequency. This is where microwave's label comes in handy. The label will have information as to what frequency the microwave emits waves at, normally in Hz (1 Hz = 1/s).
At last we can determine the speed of light!
Simply plug in the wavelength (that you converted to meters) and the frequency (that you found in 1/s). Do this, and voila! You have the speed of light in m/s. Almost. We skipped out on a branch of statistical analysis that deals with uncertainty and its propagation, but so long as you made the measurements carefully, your answer should be close to 3 x 10^8 m/s, which is 300000000 m/s.
Cool, huh? Feel free to reward yourself with that chocolate.
PS: Why this entry is related to Steins;Gate? Because MAL won't let me post it unless I had an 'anime relation'. And the most relevant anime I could find was Steins;Gate. Because microwaves and science.
The tools you will need: a microwave, a ruler, a calculator, and a bar of chocolate (yes, chocolate).
Here is a briefer on all the physics you need going into this. If you already know what a standing wave is, and how to calculate wavelength, skip to after the pink fluffy teddy bear.
1) Microwaves are part of the electromagnetic spectrum. This spectrum includes UV rays, visible light, and X rays, and can most easily be described as a bunch of things that act like visible light, with the exception that we can't see them. And like visible light, microwaves travel at speed of light.
2) Microwave ovens emit microwaves in a special configuration, called a standing wave. A standing wave is a wave that stands so perfectly fits its container that it looks like it's standing still. You have probably created standing waves as children playing with jump ropes. If you lift the rope and push at the right moment, the jump rope will have one place that goes up and down - moving into peaks and valleys, while staying still at the two ends. If you put a little more effort into it, you can make the jump rope have two places that form peaks and valleys, and three points where it appears to be 'standing'. Here is Walter Lewin demonstrating the principle.
This s-like curve is one wave, and the length of it is one wavelength.
This principle of standing waves also applies to microwaves in the oven. The points that don't form peaks and valleys are points where no oscillation occurs. This is why the microwave tray rotates: it moves the food to ensure that every part of your food is exposed to the places of highest oscillation, resulting in a more evenly heated product.
3) The number of waves that pass by a certain point per second is called the frequency of the waves. Frequency, wavelength, and the speed of waves have the following established relation:
(Frequency) x (Wavelength) = Speed
With this, you are ready to do science!
It is time.
========
Place the chocolate bar (without the plastic!) into the microwave whose rotating tray has been removed. I recommend placing the chocolate on a microwavable plate for convenience. Heat the bar until you can make out at least 2 soft spots, which are the bubbles from heating. Since the tray isn't moving, the melting will not be even. Certain points will begin to bubble while the rest of the bar will be unharmed. The ideal chocolate bar for this experiment will have a smooth surface. Once you see these soft spots, stop the heating. It should look something like this:
Use the ruler to measure the distance between those two spots (ideally measured from their centers). This is half the wavelength of the microwaves emitted by your oven. Soft spots in red:
Double that distance, and you'll naturally have the required wavelength. Now convert this number to meters. A simple Google search of "x inches to m" should suffice.
Next you need the frequency. This is where microwave's label comes in handy. The label will have information as to what frequency the microwave emits waves at, normally in Hz (1 Hz = 1/s).
At last we can determine the speed of light!
Simply plug in the wavelength (that you converted to meters) and the frequency (that you found in 1/s). Do this, and voila! You have the speed of light in m/s. Almost. We skipped out on a branch of statistical analysis that deals with uncertainty and its propagation, but so long as you made the measurements carefully, your answer should be close to 3 x 10^8 m/s, which is 300000000 m/s.
Cool, huh? Feel free to reward yourself with that chocolate.
PS: Why this entry is related to Steins;Gate? Because MAL won't let me post it unless I had an 'anime relation'. And the most relevant anime I could find was Steins;Gate. Because microwaves and science.
Posted by Hitchens | Jul 13, 2013 4:21 PM | 0 comments