Value of theta of first minimum

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Homework Help Overview

The discussion revolves around a problem involving a diffraction grating and the calculation of the angle for the first minimum using the wavelength of light and the separation between slits.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to apply the diffraction formula, but questions arise regarding the value of the slit separation used in their calculations. Some participants seek clarification on the correct value for the separation between slits.

Discussion Status

Participants are actively questioning the assumptions made by the original poster, particularly regarding the definition of the slit separation and the context of the problem. There is a suggestion that the problem may involve a single slit rather than a grating, indicating a potential misunderstanding of the setup.

Contextual Notes

There is a noted discrepancy in the values used for the separation between slits, which may affect the calculations. The original poster's reference to a figure is also mentioned but not provided, leaving some context unclear.

desmond iking
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Homework Statement


A parallel beam of monochromatic light of wavelength 580nm is incidentally normal on a diffraction grating. The separation between successive lines on the grating is 0.7μm as shown in the figure.
please refer to the photo , i am having problem with part (a)


Homework Equations





The Attempt at a Solution


my working is d sin θ = λ
sin θ = λ /d , where d is the separation between slits.. by plug in value of λ = 580x10^-9 and d = 1/ (5000x10^2) , i have my θ = 47 ° , the ans given is 56°
why am i wrong?
 

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Where are you given that value for d?
 
Last edited:
NascentOxygen said:
Where are you given that value for d?

sorry i made a typo.
here's what i mean :
sin θ = λ /d , where d is the separation between slits.. by plug in value of λ = 580x10^-9 and d = 0.7x10^-6 , i have my θ = 47 ° , the ans given is 56°
 
Part a asks about a single slit !
And the distance between slits is NOT 70 micrometer.
 

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