Young's Slit Interference (Double Slit)

[singinglupine]

Find the slit separation of a double slit arrangement that will produce interference fringes 11.5 mrad apart on a distant screen with light of wavelength 471.0 nm.

tan(theta) = y/D
asin(theta) = p * wavelength

I know that I'm trying to solve for a, and that asin(theta) = 11.5, but I feel like I don't know enough information to solve the problem. Could someone point me in the right direction?

 

[Delphi51]

The angle is θ = 11.5 mrad, the wavelength 471 nm so your expression should be more like
a*sin(11.5 mrad) = p*471 nm.
Be sure to get rid of the milli and the nano.

There is a little problem with that formula - it gives the angles for the minima whereas there is a maximum at θ = 0, so you'll have to do a couple of calculations perhaps for p = 1 and p = 2 to get a difference in angle between two minima.

 

[singinglupine]

Ah thanks. :)