Calculating the speed of light using a microwave

[mynamewastaken]

I really liked this idea for my science fair project but I'm a little confused by how you're supposed to measure the cooked egg, and the egg should be cooked in one spot but not the other am I right? Can you please help me out? Thanks in advance

[deleted-249560]

The project idea calls for microwaving the egg white until it's partially cooked, with clearly cooked spots and other spots that are less cooked. Measure the distance between the cooked spots with a ruler. It would be best if you had one that was marked in centimeters with further subdivisions for accuracy

As the instructions indicate, if you end up cooking the egg too much, start again with a fresh egg white and use less time.

[mynamewastaken]

so between the cooked and partially cooked? and if it were in a line and there was a gap in between that wasn't cooked you would be measuring the gap?

[deleted-249560]

I haven't done the experiment myself, but yes, that's what I get from reading from reading the procedure.

In the procedure description, there's a sample image showing that the centers of the cooked spots are 6cm apart. You're looking for the gap between the centers of the hotspots.

[mynamewastaken]

Okay thank you so much, I got 5cm (which is equal to 0.5dm) and when I multiplied 0.5dm by the frequency I got half of the frequency. It said the spacing of the hotspots would be half of the frequency , is the way I got half correct or should the spacing of the hotspots itself be half the frequency? Sorry for so many questions I'm just trying to figure out if the way I got the numbers are right because I did get the right numbers.

[deleted-249560]

5 cm as 1/2 the wavelength means the wavelength is 10 cm or 0.1 meters. The speed of light (c) is 300,000,000 m/s and wavelength*frequency=c. Or, frequency=c/wavelength. 300,000,000/0.1 = 3,000,000,000 Hz or 3000 MHz. That's a bit higher than the generally known frequency of 2450 MHz, but it's close.

The procedure described was pretty clear but perhaps there are other reasons for the discrepancy. I tried it with our microwave (a larger micro/convention thing from 1989) and the hotspot patterns were nothing like the procedure described. Our microwave has a wave stirrer which is a reflective fan designed to bounce the waves all over the oven. It had hotspots but none that were spaced approximately 5 or 6 cm apart.

You ran several trials and got the 5cm repeatedly? Then just go ahead with that and write up your results.

Howard

[mynamewastaken]

I meant I got 5cm as the wavelength, and when i multiplied the wavelength by the frequency the sum was half of the frequency. Since 5cm is 0.5dm I did 0.5dm x 2450 = 1,225 (2450/2 = 1,225)

[deleted-249560]

The wavelength times the frequency is the speed of light. You measured 5 cm which is 1/2 of the wavelength, or 10 cm = 0.10 m. 2450 MHz = 2450000000 Hz. 0.10 * 2450000000 = 245000000, or 245,000,000 meters/sec which is close, but not quite the actual number: 300,000,000 meters/sec. When you present your data, can you think of reasons why your result might be off a bit?

[mynamewastaken]

Thank you! and I got results ranging from ~4.5cm to ~5.5cm but 5cm was the most frequent result, should it have been higher or lower? I will check if my microwave has that function/setting you were saying yours did

[deleted-249560]

For a microwave running at 2450 MHz, the 6cm shown in the image in the project idea is what we'd expect. Try the math with a measurement of 6 cm and see how it works out.

[mynamewastaken]

Hi again, I'm in my final stages of the project and the data seems it would be Quantitative (having numbers and measurments) but I'm not so sure if this can be graphed since the data is supposed to all be the same set of numbers

[deleted-249560]

You have the data from the multiple trials. If you graphed the results, the graph would show how your measurements were on either side of your average number. That may be the best you can do.

[mynamewastaken]

So for the question I used how does wave speed, frequency and wavelength relate (question giving on the topic outline) but i didn't know how to make it work because of the three variables so I was going to do how does frequency and wavelength relate ? knowing that as frequency goes up wavelength goes down and vice versa but somehow frequency is the independent variable for me because you can't change the frequency of your microwave? so I'm really stuck here

[deleted-249560]

That's an excelllent point. The microwave is always at the same frequency, so you can only discuss the relationship in general (show the equation, etc) and then offer up your table of experimental data and graph as evidence that you were able to measure it. Not all experiments have an easily manipulated IV. The same might be said for experiments where you're trying to discover something like a cure for a disease. You try something. When it fails, you try something else. When you eventually find something that works, you're done.

There is a lot of background information you can choose from to present here as well. I think you won't have any difficulty finding good information to write up. Pictures of your egg whites will also help tell your story. But yes, it's true that you couldn't manipulate the frequency component here - that's how it goes sometimes.

Howard