1. The problem statement, all variables and given/known data A student collects diffraction data using a lamp with known emission wavelengths of 425nm, 565nm, 600nm, and 700nm. These lines appeared on her spectroscope at 32mm, 59mm, 63mm, and 69mm(all measured from the same arbitrary 0mm position). With these data she is able to calibrate her spectroscope, and using this calibrated spectroscope she observes another lamp that has an emission line at 55mm. What is the wavelength of this emission line? (Use Excel to generate an equation of a line with a properly labeled graph) 2. Relevant equations dsin(θ) = m (λ) 3. The attempt at a solution In the equation above, I am provided with two out of four variables - I don't have the diffraction grating difference, nor do I have the angle at each wavelength. What I thought is this: sin(theta) = x (spacing between bright fringes, i.e 32mm) / L (path length). If I substitute it in to the equation above, I would get dx / L = m (λ). I still am missing two variables. Even if I had tan(θ) = x(fringe spacing) / L, and I assumed sin(θ) ~ tan(θ) as the angle is small, I'm still utterly confused. Now I attempt to address the last part of the problem in parentheses - plotting the equation - I had thought that in mλ = dsinθ, I would be able to find the slope to be some variable, but it seems I am still at a disadvantage without more information in the problem. Any tips? I'd appreciate anything - better just tips rather than the whole solution if possible; I still want to try and arrive at the solution myself.