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## Homework Statement

A double-slit interference pattern is observed on a screen 1.0m behind two slits placed on 0.3mm apart. Ten bright fringes span a distance of 1.65cm. What is the wavelength of the light?

## Homework Equations

Since we're looking at bright fringes:

(m+1/2)[tex]\lambda[/tex] = dsin[tex]\theta[/tex] = d(x/L)

## The Attempt at a Solution

d = 3E

^{-4}m

m = 4 (I feel like I'm supposed to use just one half of the bands, excluding the middle band. Is this right? Why do I do this?)

L = 1.0m

y = 8.25E

^{-3}m (this is the spread of the 10 fringes divided by 2 since I'm using half of them)

(m+1/2)[tex]\lambda[/tex] = d(x/L)

(4+1/2)[tex]\lambda[/tex] = 3E

^{-4}(

**8.25E**/1.0)

^{-3}[tex]\lambda[/tex] = 5.5E

^{-7}m

On my formula sheet there is an 'x'...the variable for the spread of the fringes is traditionally 'y'...I figured they were just the same thing so used y for x in the above example. If that's wrong then could someone explain where I get 'x' from? Any explanation would be appreciated.

Thanks!