Single Slit Diffraction

 This applet shows the simplest case of diffraction, i.e., single slit diffraction. You can change the color of the light by draging or clicking the spectrum selector. You may also change the width of the slit by dragging one of the sides. 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.