1. The problem statement, all variables and given/known data Some microowaves (EM radiation) have wavelength of 3 cm. What would be the order of magnitude of grating spacing needed to observe these ? 2. Relevant equations n[tex]\lambda[/tex] = d sin[tex]\theta[/tex] 3. The attempt at a solution First of all, I am not really sure if I was using the correct equation for that question but all what I am doing is about the diffraction grating spectrometer, gas spectra wavelength of light. In that question there was no angle so I can find n. The only thing is the wavelength given. I do not want you to solve it. I just want you to lead me to where should I go ?