Calculate the grating spacing,a , using the data of Step P1, where you recorded n, the number of ruled lines per unit length of the diffraction grating. (b) Describe the grating spacing,a , by sketching an enlarged version of a typical diffraction grating. (c) What do the "lines" on the diffraction grating represent? What is their purpose? W2. (a) Draw a sketch showing the major parts of the grating spectrometer used in the experiment. Describe their functions. (b) Specify a natural phenomenon that exhibits a similar spectrum of a white-light source like what you observed in Step P2, and briefly discuss how it is formed. Does it also possess the higher- order spectrums that you saw in Step P2? Explain. W3. Determine the wavelengths of the spectrum of the Hg source you used in Step P3. In Eq. (19.1), use the value ofa calculated in Question W1 above, and take as half the difference between the absolute left position,L , and the absolute right position,R , i.e.L R ( ) . One must use this averaged value for to take into account the possibility that the diffraction grating was not precisely oriented perpendicular to the zeroth-order beam, which would cause