This Demonstration allows you to visualize the diffraction pattern of light coming through a single-slit source, which illustrates the wave nature of light. The maxima represent the bands where the light appears on the screen (solid radii) while the minima represent the bands where no light occurs (dashed radii).
You can vary the wavelength of the visible light source and the width of the slit. The color of the light changes with respect to the wavelength. The max/min slider allows you to traverse the maxima and minima values. The angle is where the maximum or minimum is located.