** Missing info: Lines per mm = 500 **
Ans: The wavelength is = λ = 1414.21 nm
Explanation:
The formula for diffraction grading is:
dsinθ = mλ --- (1)
Where
d = 1/lines-per-meter = (1/500)*10^-3 = 2 * 10^-6
m = order = 1
λ = wavelength
θ = 45°
Plug in the values in (1):
(1) => 2*10^-6*sin(45°) = (1)λ
=> λ = 1414.21 nm
