A mask with many, many slits equally spaced is called a
A diffraction grating produces many narrow bands of nearly equal brightness; bright spots occur at any angle for which
d sin(theta) = m lambda m = 1, 2, 3, ...
where "d" is the spacing of the slits
Light of different wavelengths will produce bright spots at different angles after passing through a diffraction grating; the grating creates a rainbow spectrum
of a diffraction grating is a measure of its ability to separate light of nearly equal wavelengths; it is equal to the number of slits times the order of the spectrum