# Double Slit Interference Question

## Homework Statement

Light of wavelength 680 nm falls on two slits and produces an interference pattern in which thefourth-order fringe is 38 mm from the central fringe on a screen 2.0 m away. What is the separationof the two slits?

## Homework Equations

Sin$$theta$$=2m($$\lambda$$2d)

x=L($$\lambda/d$$

## The Attempt at a Solution

My givens are:
$$\lambda$$= 680nm
L= 2.0m
x438mm

using equation x=L($$\lambda/d$$ I got:

0.038 = 2.0m(680 x 10-9(4)/d)
d=2.0m(680 x 10-9(4)/d)/0.038)= 1.4x10-4m

Am I doing this correctly?

Thanks.

collinsmark
Homework Helper
Gold Member
I got:

0.038 = 2.0m(680 x 10-9(4)/d)
d=2.0m(680 x 10-9(4)/d)/0.038)= 1.4x10-4m

Am I doing this correctly?
That's how I did it. collinsmark
Homework Helper
Gold Member
I got:

0.038 = 2.0m(680 x 10-9(4)/d)
d=2.0m(680 x 10-9(4)/d)/0.038)= 1.4x10-4m
Oh, except you left the "/d" in there. But I'm guessing that's just a typo. Last edited:
Thanks! Definitely a typo, sorry about that.