Destructive interference and fringes

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Homework Help Overview

The discussion revolves around calculating the distance between the 2nd and 3rd dark fringes in a double-slit interference pattern using monochromatic, coherent light. The original poster presents a formula involving the distance between slits, wavelength, and distance to the screen, but expresses uncertainty about its correctness.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to apply a formula for destructive interference but questions its validity. Some participants inquire about the reasoning behind the perceived error in the formula.

Discussion Status

The discussion includes a moment of realization from the original poster regarding a unit conversion error, indicating a productive direction. However, further questions about related topics suggest ongoing exploration.

Contextual Notes

The original poster mentions a second question related to interference in a film, indicating multiple areas of inquiry within the same thread.

Joza
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I am looking for the distance between the 2nd and 3rd DARK fringes on a screen.

Monochromatic, coherent light is shone through 2 slits a distance d apart.

Wavelength is L. Distance between grating and screen is R.

The formula I am using is: [(R(5/2)L)/d - (R(3/2)L)/d]

I am using 5/2 and 3/2 since these should be the number of wavelengths for destructive interference for the 3rd and 2nd fringes respectively.

The formula doesn't seem to be working though. Where have I gone wrong?
 
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BUMP!:approve:

Come on guys. Any help? I really need to get this sorted today.
 
Your formula looks OK to me. Why do you think its wrong?
 
I feel like an idiot.


Ah it was a classic unit conversion error!:blushing:


Thanks tho!
 
D'oh! (Been there, done that.)
 
Could you help me with my final part so?
 
Joza said:
Could you help me with my final part so?
Final part of what?
 
I have 2 questions relating to light. This is one. I have posted the other. It is do with interference in a film.

Please excuse the posts in the thread. The first one relates to the question.
 

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