
#1
Jan2613, 03:35 AM

P: 196

hi...
Got to ask about superpostion of waves... When two coherent light waves cross each at some point in space moving in different directions, do they superimpose? If they do, do we need a screen to be able to see the resultant or we can see it directly. Let's just assume we have a laser and with some sort of mirror arrangement we make the incident ray meet the reflected ray. The point where they meet can we see constructive or destructive interference (assuming 100% reflection and no losses)? Thanks for any help! 



#2
Jan2613, 07:00 AM

Mentor
P: 16,466





#3
Jan2713, 01:53 PM

P: 196

Thanks..
Looks like I got what I wanted. 



#4
Jan3013, 11:19 AM

P: 196

Superposition of waves, result visible?
can i ask one more thing here?
If i have a laser pointing towards the mirror, there will be superposition of light after it retraces its path. If a glass plate of negligible thickness is placed in between obliquely, then can we obtain the result of superposition in the form of interference fringe pattern. In this if we have assumed the light wave to be continuous (which it is for classical purposes) this pattern should be obtained in for any distance between the plate and the mirror. But there comes coherence length into picture. If light is continuous how does the path difference affect the result in any way?? 



#5
Jan3013, 01:26 PM

Mentor
P: 16,466

I am not sure that I understand what you are asking.
Are you asking about the length of different paths within the coherence length or are you asking about what happens after you are outside of the coherence length or are you asking about what happens as you move from within the coherence length to outside it? 



#6
Jan3113, 05:13 AM

P: 34

If you build an interferometer then you are splitting light into two arms and then recombining it. Roughly speaking, if the difference in the optical path lengths between the two arms is shorter than the coherence length then you will see interference  if it's longer then you won't. In practice it's not a sharp cutoff of course  it has a profile which is related to the Fourier transform of the source spectrum. If you're asking why the coherence length affects whether or not you see interference then I'm happy to explain that, although it involves either some maths or a fairly conceptually difficult written explanation. 



#7
Jan3113, 08:04 AM

P: 196




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