Science Buddies: "Ask an Expert"

This project asks you to use the following equation:
wave speed (v) = frequency x wavelenth

the frequency is found on the back of the microwave oven, however, the project states that the distance between the hot spots will be equal to half on the wavelength of the microwaves.

I am not sure how to determine the wavelenth. What numbers should I be using to determine the wavelength?

wave speed = 2450 MHz x ? wavelength

How do I figure the wavelength number?

Hello inquisitive,

As is explained in the project description, you measure the spacing of the most-cooked spots. The spots are a half-wavelength apart, so the wavelength is just twice the distance between the most-cooked spots.

Some microwave ovens contain devices to constantly move the "hot spots" around to give more uniform cooking. If you don't see regularly spaced spots, maybe you could try another microwave.

Good luck, WW

i am still confused on this topic the math is confusing and you just repeated what the confusing experimental procedure said

how would you go about doing this project the math is really confusing what are you supposed to do

username 48,

As you noted in your original question, "wave speed (v) = frequency x wavelenth."

You read the frequency from the microwave label. I replied that "The spots are a half-wavelength apart, so the wavelength is just twice the distance between the most-cooked spots."

So you have the frequency, you can measure the distance between two spots and you just multiply those numbers. If you still don't understand how to get the wave speed, before I can help you I need to know much more specifically what you don't understand.

WW

so what youre saying is that one would multiply the hot spots by two so if the portions of the hotspots were 16cm across and the microwave was 2450mhz i would multiply the hot spot by 2 and then multiply the 32 times 2450 to get my answer?

username 48,

You've got it except that instead of multiplying by 2450, you multiply by 2,450,000,000. The 2450 is in units of megaHertz (mHz) so the number is 2450 x 1,000,000.

WW

Is there an independent variable in this project? I don't think there is.

inquisitive,

You're right. Since the experiment measures an invariant value, the speed of light, and you can't change the frequency of the microwave, it's just a point measurement.

WW

in the experiment it says the error of measurement... what is the purpose of finding the error of measurement

also i forgot to ask what is the error of measurement exactly

We may define error of measurement as the difference between a measurement taken by the scientist (in this case, you) and an approximate measurement. If you haven't been familiarized with finding error of measurement, percent error, margin for error, etc. for your labs at school or for experiments at home, you will soon. They are extremely important because they gauge how well (or not so well) the results of an experiment have turned out. For instance, you would not want to end up with a high error of measurement or a high percent error because that means that something went wrong with the experiment, perhaps because of human errors or even inherent flaws in the procedure, making your experimental values quite different from the accepted values. Oftentimes, we perform many trials for experiments so that we receive consistent results that allow our work to have validity. Error calculations and determining sources of error thus play an essential role in our understanding of an experiment, and may very well reflect the amount of work and effort we put in, as well.