physics - waves

[cool dude]

my teacher said that it is easier to meaure the wavelength of a wave using the standing wave interference pattern than it is to meaure it directly. she tried to explain but i'm still not too sure why since if i just took a ruler and measure from crest to crest or trough to trough i would get the wave length, so why is it easier to get wavelength by using the standing wave interference?.

[1of42]

Since when were you able to stop a crest long enough to reliably measure it?

This thread reminds me of my favorite physics experiment eevr - finding out the speed of light by melting a piece of cheese in a microwave.

[chrispminis]

1of42 wrote:

Since when were you able to stop a crest long enough to reliably measure it?

This thread reminds me of my favorite physics experiment eevr - finding out the speed of light by melting a piece of cheese in a microwave.

EXPLAIN!

[Tony]

cool dude - when the wave is "standing", then you can measure from crest to crest. Any other type of interference will make the wave bounce back with a different offset than the first first and the result will no longer be in wave-like shape.

1of42 - do explain

[cool dude]

thanks. so its like constructive interference where the waves amplitute would get bigger or smaller and as a result of the amplitute change it will be difficult to measure it directly. the only thing i'm not too sure on though is wat exactly is a standing wave interference pattern. is it when the waves interfere destructively to cause nodes which are always in the same position therefore if we measure from node to node and multiply by 2 we can get wavelength?

[Tony]

that's right

Wikipedia has a pretty awesome animated picture to demonstrate the concept

[1of42]

Equipment: Standard microwave, plate, piece of cheese, ruler.

Microwaves list the frequency that they operate on on their backs. So there's the frequency for you.

Melt the piece of cheese in the microwave, and you will get a pattern of melting on the cheese that corresponds to an interference pattern from the standing wave pattern established in the microwave. By measuring the distance between two adjacent highly-melted places on the piece of cheese (antinodes of the wave), you get wavelength of the wave.

Since EM waves travel at the speed of light, from this you calculate the speed of light - v=f(lambda). Obviously it's a little rough, but I got only about a 5% error for the experiment, which is decent.

[person]

1of42 wrote:

By measuring the distance between two adjacent highly-melted places on the piece of cheese (antinodes of the wave), you get wavelength of the wave.

but doesnt the plate spin?

[Cervantes]

If you're doing a physics experiment, you should at least be able to stop the microwave plate from spinning...

[Mazer]

Not everyone has a turning table in their microwaves.

Regardless, I'm pretty disgusted with you 1of42. Cheese > Science, surely you know that!

[1of42]

person wrote:

1of42 wrote:

By measuring the distance between two adjacent highly-melted places on the piece of cheese (antinodes of the wave), you get wavelength of the wave.

but doesnt the plate spin?

I probably should have remembered to say that non-turntable microwaves are best

[person]

wait, there r none turning microwave plates?
wouldnt the food get cooked rlly badly?

[1of42]

person wrote:

wait, there are non-turning microwave plates?
wouldnt the food get cooked really badly?

fixed all the horrendous short forms.

as for your answer: i suppose it would, but I don't really think it's relevant

[chrispminis]

Regardless, witches need burning.