Diffraction is a phenomenon which envolves the bending of waves around obstacles.
It's generally guided by Huygen's Principle, which states: every point on a wave
front acts as a source of tiny wavelets that move forward with the same speed as
the wave; the wave front at a later instant is the surface that is tangent to the
wavelets. If one considers diffraction through a slit then the properties of the
system are wholly dependant on the ratio **λ/w**, where **λ** is
the wavelength of the light and **w** is the width of the slit. If one maps the
intensity pattern along the slit some distance away, one will find that it consists
of bright and dark fringes. In the middle a central bright fringe can be found,
it is the largest bright fringe. The angle at which the dark fringes occur is given
by **sin θ = m(λ/w)** where **m ∈ {1,2,3,....}**. As you see,
the intensity pattern is determined only by the ratio **λ/w**. Notice the
effect of both the slit width and wavelength by dragging the slit sides and spectrum
selector, respectively.