How Far is the Third Interference Minimum in a Double Slit Experiment?

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Homework Help Overview

The problem involves a double slit experiment where light of a specific wavelength passes through slits and creates an interference pattern on a screen. The original poster seeks to determine the distance from the center of the pattern to the third interference minimum.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to calculate the position of the third interference minimum using given parameters and equations related to interference patterns.
  • Some participants question the original poster's interpretation of the interference order, suggesting a need to adjust the value of m to find the minimum instead of the maximum.
  • There is a discussion about the relationship between maximum and minimum orders in the context of the problem.

Discussion Status

Participants are actively engaging with the problem, with some providing guidance on interpreting the order of interference. The original poster appears to have reached a conclusion regarding the correct order for the minimum, although the discussion remains open to further exploration.

Contextual Notes

The original poster's calculations initially led to an incorrect identification of the interference order, which prompted clarification from other participants regarding the definitions of maxima and minima in the context of the experiment.

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Homework Statement



Light of wavelength = 655 nm passes through a pair of slits that are 245 µm apart and travels to a screen 9.0 m away. How far from the center of the pattern is the third interference minimum? (in mm)

d=245e-6
λ=655e-9
m=3
D=9
y=distance from center of 3rd interference minimum

Homework Equations



sinθ=λm/d
tanθ=y/D

The Attempt at a Solution



sinθ=λm/d=(655e-9)(3)/(245e-6)
θ=0.4595 degrees

tanθ=y/D
y=Dtanθ=9tan(0.4595)
y=0.722m=72.2mm (incorrect)
 
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Hi Wahsup, welcome to PF!
It seems to me you have found the 3rd maximum, but the question asks for the MINIMUM. You'll just have to adjust your m value.
 
Delphi51 said:
Hi Wahsup, welcome to PF!
It seems to me you have found the 3rd maximum, but the question asks for the MINIMUM. You'll just have to adjust your m value.

thanks!

if m=3 is the max, would that mean m=2 is the min?
 
nevermind. i got it.

Since m=3 is the max, the min is m=2.5

thank you for the help
 

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