Diffraction gratings and equationsWatch
Based upon the close proximity of said slits a very sharp interference pattern is produced (much better and clearer than with Young's Double slits) when a source of monochromatic and coherent light is passed through it.
This is due to the fact that there's such a large proportion of diffraction gratings interfering (experiencing superposition).
Waves that meet 180 degrees out of phase experience destructive interference and so produce a sharp minimum (dark point), and light rays that meet in phase (or 360 degrees out of phase) experience constructive interference and so produce a sharp maxima (bright point).
The diffraction grating equation is (for my spec - AQA):
n = d sin( )
n = the order of the beam produced
d = distance between two slits in the diffraction grating (often extremely small)
= the wavelength of the incident light being diffracted by the grating.
= the angle between the order beam in question (a maxima) and the zero order (normal).
n / d = sin( )
We can see this when we rearrange the diffraction grating equation.
We can therefore say as we increase diffraction increases (the waves spread out more) and so is greater - all just from looking at the grating equation