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The question illustrates mono-chromatic red light passing through 2 slits and forming an interference pattern on the screen. The question then asks to suggest a suitable value for the slit separation.

How do I find a value for this or what basis should I approximate my answer?

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closed as too localized by John Rennie, Waffle's Crazy Peanut, David Z May 27 '13 at 17:00

This question is unlikely to help any future visitors; it is only relevant to a small geographic area, a specific moment in time, or an extraordinarily narrow situation that is not generally applicable to the worldwide audience of the internet. For help making this question more broadly applicable, visit the help center.If this question can be reworded to fit the rules in the help center, please edit the question.

I've added the homework tag. In the future, please use this tag on homework questions. – Ben Crowell May 26 '13 at 20:03
this answer cannot be solved with this information! i am pretty sure you are going to need some information such as which angles dark or bright fringes appear. – phaedrus May 26 '13 at 20:46
I think it should just be comparable to the wavelength $\lambda$ – ABC May 27 '13 at 14:51
up vote 0 down vote accepted

I suppose the question must be read as asking for a ballpark figure of what would be a reasonable slit separation to use to observe an interference pattern at reasonable angles. You will need to do something like the following:

  • Decide on what angle you would like to observe the first intensity maximum at
  • Find a formula relating the angle of the first maximum to slit separation (I bet that's easily found on wikipedia or in most textbooks on the subject)
  • Find out what the wavelength of "red light" is
  • Use the information you have from above to calculate the slit separation.

When doing the above, you should feel free to use approximations and round off numbers you look up. Good luck!

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