Propagation of Error for Sodium Doublet Lines

[Browntown]

Homework Statement

I need help propagating the error in a formula

Relevant Equations

Δλ = (λ^2
/ 2Δd)

The equation we used in this lab was Δλ = (λ^2 / 2Δd) where Δλ is the separation of the sodium D doublet lines and is the value we're trying to calculate, λ^2 is the wavelength of sodium light given in the lab manual (589 nm) and Δd is the distance one of the mirror moves to go from one faint spot in the interference pattern to the next.

The part I'm confused with is we've been told to propagate the error for Δλ but the only value we have in the formula that has an uncertainty is Δd. I've tried many different formulae to propagate the error but I keep getting wrong units, no units, etc..

If someone could give me some advice that would be awesome. Thank you!

 

[Orodruin]

Please show your work.

 

[Cutter Ketch]

Surely you wouldn’t be asked to propagate error without someone at sometime telling you how to propagate error. Do you not have some formulae or instructions related to error propagation?