Double Slit: Find Longest Wavelength

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Homework Help Overview

The discussion revolves around calculating the longest wavelength of light that can produce a first-order maximum in a double-slit experiment, with slits separated by 1200 nm. Participants are exploring the implications of the wavelength in relation to the double-slit setup and its position in the electromagnetic spectrum.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants are questioning the use of the formula sin(theta) = m(wavelength)/d, particularly the role of the angle theta and how it relates to the maximum wavelength. There is also discussion about the implications of the angle being constrained between -90 and 90 degrees.

Discussion Status

The discussion is ongoing, with participants attempting to reconcile the provided answer from a book with their own reasoning. Some participants express confusion about the calculations and the validity of the book's answer, while others are exploring the relationship between the slit separation and the wavelength.

Contextual Notes

There is uncertainty regarding the correctness of the book's answer, with some participants suggesting that it may be incorrect due to a possible oversight. The constraints of the problem, including the separation of the slits and the nature of the first-order maximum, are under consideration.

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Question: Calculate the longest wavelength of light falling on double slits separated by 1200nm for which there is a first-order maximum. In what part of the spectrum is the light?

Answer in Book: 12nm

my problem: the formula i thought you would use is sin(theta) = m(wavelength)/d?? However you do not know an angle? any ideas??
 
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Of course -\frac{\pi}{2} < \theta < \frac{\pi}{2}. Can you solve it now?
 
yeah i get what that means and that theta could not be greater then 90 or less then -90, so then how do i incorperate that into the equation? and get 12 nm?:confused:
 
Plugging theta in would give

\lambda _{max} \approx d

Which according to your book is wrong. I'm stunned. I suppose the answer in the book is wrong: they've forgotten the zeros.
 
so the biggest possible wavelength that could be created would be slightly under the width between the two slits?? and thanks a lot for your help:smile:
 

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