How Do You Derive the Diffraction Formula nλ = d sinθ?

[pianogirl]

Homework Statement

Basically there's a question that I'm doing which asks me to show how to derive:
n lambda=d sin theta
We haven't learned it yet and so how do you do it?

Homework Equations

n lambda=d sin theta

The Attempt at a Solution

Not a clue!

Thanks!

 

[Delphi51]

Take a look at this explanation
http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/slits.html#c1
Basically the little triangle with the δ in it is similar to the big one with the D and y, as long as D is very large. You write a sinθ formula for both of them and combine them to get the formula you want.