![]() The illustration shows the hydrogen spectrum. It acts as a "super prism", separating the different colors of light much more than the dispersion effect in a prism. The diffraction grating is an immensely useful tool for the separation of the spectral lines associated with atomic transitions. However, angular separation of the maxima is generally much greater because the slit spacing is so small for a diffraction grating. The condition for maximum intensity is the same as that for a double slit. The relative widths of the interference and diffraction patterns depends upon the slit separation and the width of the individual slits, so the pattern will vary based upon those values. The overall grating intensity is given by the product of the intensity expressions for interference and diffraction. The intensities of these peaks are affected by the diffraction envelope which is determined by the width of the single slits making up the grating. There are multiple orders of the peaks associated with the interference of light through the multiple slits. This illustration is qualitative and intended mainly to show the clear separation of the wavelengths of light. ![]() Different wavelengths are diffracted at different angles, according to the grating relationship.Ī diffraction grating is the tool of choice for separating the colors in incident light. Orders 1 and 2 are shown to each side of the direct beam. When light of a single wavelength, like the 632.8nm red light from a helium-neon laser at left, strikes a diffraction grating it is diffracted to each side in multiple orders. The peak intensities are also much higher for the grating than for the double slit. The condition for maximum intensity is the same as that for the double slit or multiple slits, but with a large number of slits the intensity maximum is very sharp and narrow, providing the high resolution for spectroscopic applications. A large number of parallel, closely spaced slits constitutes a diffraction grating. ![]() This "super prism" aspect of the diffraction grating leads to application for measuring atomic spectra in both laboratory instruments and telescopes. For example, with values of n=4 (35.5°) and n=5 (46.6°) for the blue light I get wavelength values that both round to 436nm, but this is apparently incorrect.Īlso I don't understand how the two yellow maxima are so close together because this would normally mean there is a tiny wavelength, much smaller than that of visible light.When there is a need to separate light of different wavelengths with high resolution, then a diffraction grating is most often the tool of choice. I have tried guessing numbers to make sure the wavelengths are in the range 400nm to 700nm. However, I'm not sure where to go from there as I don't know what order of maxima they are as 0° to 30° is not examined. So for the first angle: $n\lambda = 3 \times 10^ \times sin 32.7$ To calculate wavelengths, I know that: $n\lambda = dsin \theta$. No other maxima are observed in this range of angles. The spectrum is examined over the range of angles from 30° to 50°, and maxima of intensity are observed at the angles and with the colours shown in the table. ![]() I am having some problems calculating wavelengths from some given information about a grating spectrum.Ī diffraction grating with a spacing of 3μm is used in a spectrometer to investigate the emission spectrum of a mercury vapour discharge lamp.
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