interference

[kidia]

I have one question here which I need clarification.

Automobile has two headlights. What sort of interference pattern do you expect to see from them?

[insane_alien]

none they are not coherent lights. interference only works if you use a laser

[s pepperchin]

There is interference but it isn't distiguishable. Each wavelength has its own pattern and they all overlap each other.

[insane_alien]

so basically there are uncountable trillions of patterns that absorb into a general indistinguishable mishmash. or, no.

[s pepperchin]

yes, but there is still interference.

[kidia]

none they are not coherent lights. interference only works if you use a laser

 

Remember that headlights always coming from same light source how can it be incoherent?

[s pepperchin]

none they are not coherent lights. interference only works if you use a laser

 

a laser is not required for interference. The original experiment was done with a candle and if you do it right you can see a interference pattern from look at a light sourse through the small gap between your fingers. try it with your index and middle finger.

[[Tycho?]]

Remember that headlights always coming from same light source how can it be incoherent?

 

Two different filaments, two different panes of glass, different amounts of dirt and stuff on them. They may be in phase, then again they may not be. Your getting a ton of different wavelenths moving in all kinds of different directions be reflected and refracted all over the place. As was pointed out, interference will occur, but I dont think there would be much of an interteresting pattern coming out of it.

[kidia]

'']Two different filaments, two different panes of glass, different amounts of dirt and stuff on them. They may be in phase, then again they may not be. Your getting a ton of different wavelenths moving in all kinds of different directions be reflected and refracted all over the place. As was pointed out, interference will occur, but I dont think there would be much of an interteresting pattern coming out of it.

 

OK,from your point ,if we take another similar example of sound waves abtained by driving two different loudspeakers from the same audio source They may be in phase, then again they may not be.Because we have different speakers,different amounts of dirt and stuff on them,IS IT?

[Bettina]

Ummm.... my teacher did this with a bulb and a piece of cardboard. Check this out. You will need Java.

 

http://www.mic-d.com/java/doubleslit/index.html

 

Bettina

[s pepperchin]

Another example you can use for this is go to radio shack and get the piezo electric buzzers (or however you spell it) and hook them up so that they are in parallel, but hook the red wire from one to the black wire of the other. When you do this you can set them a integer number of wavelengths plus a half wavelength and they will interfere with each other and you will not hear the buzzing. Found that out accidently in a physics lab once.

[m4rc]

To get an interference pattern, you must have a constant phase difference between the two sources. This can be accomplished in two ways. One way is to use two coherent sources of light (two lasers). If you use two incoherent sources of light, the phase difference between the two sources is not constant so no pattern is made. So your headlights do not make an interference pattern.

 

Another way to get interference is to use a single source of light and have it interfere with itself. You can make a single source look like two sources by using mirrors and/or slits. In this case, if the phase of the source changes (as it will in an incoherent source), it will change by the same amount for each path.

[swansont]

Remember that headlights always coming from same light source how can it be incoherent?

 

Light from a filament is generally incoherent. There is no mechanism that would make any one photon have a fixed relationship in wavelength or phase with another photon.