600 nm, we can infer that the grating spacing is about 1.8 μm. Semi-quantitative explanation A simple grating consists of a series of slits in a screen. If the light travelling at an angle from each slit has a path difference of one wavelength with respect to the adjacent slit, all these waves will add together, so that the maximum intensity of the diffracted light is obtained when: This is the same relationship that is given above. See also Fraunhofer diffraction equation Diffraction Huygens–Fresnel principle Kirchhoff's diffraction formula Fresnel diffraction Airy disc Fourier optics References Sources External links Fraunhofer diffraction on ScienceWorld Fraunhofer diffraction on HyperPhysics Diffraction Physical optics