interference pattern, wavelength

[muffintop]

1. The problem statement, all variables and given/known data
Suppose the interference pattern shown in the figure is produced by monochromatic light passing through two slits, with a separation of 127 µm, and onto a screen 1.14 m away. What is the wavelength?http://www.webassign.net/walker/28-34.gif


2. Relevant equations
wavelength = (dsin\theta) / m
y=Ltan\theta


3. The attempt at a solution
\theta= arctan (y/L) = arctan (.023 / 1.4) = .941
then plugged it in to get wavelenth. i used m = 2 for 2 slits
wavelenth = 127 x 10^-6m x sin .941 / 2

i think I have m wrong?

[rl.bhat]

i used m = 2 for 2 slits
m is not the number of slits. It is the order of the fringes starting from m=0 for the central bright fringe.