A beam of red light of wavelength 
is incident normally on a diffraction grating and produces a diffraction pattern on a screen placed parallel to the grating. The beam of red light is replaced with a beam of electromagnetic radiation of wavelength 
, which is incident normally on the same diffraction grating. The third-order maximum for the electromagnetic radiation of wavelength is at the same position on the screen as the second-order maximum for the red light. What is wavelength ?
