Fringe pattern of a vapour lamp

[aurao2003]

Homework Statement

Hi
Please, what fringe pattern would be obtained with a sodium vapour lamp?

Homework Equations

The Attempt at a Solution

I am guessing that a dominant yellow colour would be obtained. The sodium is almost acting like a monochromatic light and therefore has a particular wavelength. But I am not sure how correct my answer is. Also, what will the sketch look like? Please comment

 

[NobodySpecial]

What is the setup?
You don't have fringes from just a lamp on it's own