This application shows the Bragg's diffraction model as it was introduced by William Henry Bragg (1862-1942) and his son William Lawrence Bragg (1890-1971). The applet shows two rays incident (with wavelength λ, and angle θ) on two atomic layers of a crystal, e.g., atoms, ions, and molecules, separated by the distance d. The layers look like rows because the layers are projected onto two dimensions and your view is parallel to the layers. The applet begins with the scattered rays in phase and interferring constructively. Bragg's Law is satisfied and diffraction is occurring. The meter indicates how well the phases of the two rays match. The small light on the meter is green when Bragg's equation is satisfied and red when it is not satisfied.

2 d sen θ = n λ

The meter can be observed while the three variables in Bragg's are changed by clicking on the scroll-bar arrows and by typing the values in the boxes. The d, λ and θ variables can be changed by dragging on the arrows provided on the crystal layers and scattered beam, respectively.