Single-slit Diffraction Question Pls help

[9giddjl]

Homework Statement

Monochromatic light of 585 nm is shone on a slit of width 8.0 x 10^-2 mm and the interference pattern is produced on a screen 1.8 m from the source. What is the width of the first-order bright fringe?

Homework Equations

PD/w=x/L

The Attempt at a Solution

PD=? I am not sure what n would be.. that's my main problem
wavelength= 5.85 x 10^-7 m
L= 1.8 m
w= 8 x 10^-5 m


When I used n=1 wavelength, i got the right answer, but n=1 is the first order dark fringe.. can someone please explain to me this.. i would just like to know what n would be.. thankyou any help is muchly appreciated.

thankyou xie xie ni mm goi!

 

[Hootenanny]

but n=1 is the first order dark fringe

Why do you think that?

Doesn't n refer to the n^th maximum?

 

[mrblister68]

single slit diffraction equations lead to dark fringes, however as the separation between two dark fringes and two bright fringes are the same, it does not make any difference