Question

What do you mean by missing order? Cite example. Differentiate between prism and grating spectra.

Answer 1

The basic difference between the two is that the grating spectrum is due to diffraction and dispersion spectrum is due to dispersion.
We can hardly get higher order spectrum peaks in dispersion spectrum(only of order 1) but in grating spectrum we get higher order peaks(we can see of order 2 too).
Dispersion spectrum is continuous spectrum but Grating spectrum has line spectrum.
In dispersion spectrum red end will be closer to the direct ray but in grating spectrum violet end will be closer to the direct ray.