Interactive Tutorial about Diffraction
Interactive example : Bragg's law

Basic examples
Single atom
Pair of atoms
Row of atoms

Interactive examples
1D crystal builder
Polygons of atoms
Different atoms
Ewald sphere
Bragg's law


This example simulates the interference between two waves scattered by atoms located on two parallel layers. It is an interactive version of the graph that is used in many textbooks to explain Bragg's law.

The atom in the lower plane is fixed at the x-coordinate zero, the atom in the upper plane may be located at a different x-coordinate.

The incomming plane wave is scattered by each atom individually. The two scattered waves are plotted using the Bragg angle THETA that you provide. The resulting wave is the sum of these two waves and plotted as green wave.

As in the previous example, the oszillations are plotted normal to the wave vectors. Ideally these shoud be plotted normal to your computer screen, yet we still have to wait for proper holography to work... I'll beam it up once that works...

Start exploring and try to answer the questions below: For your first trials you should keep all parameters at their default values and just change the Bragg angle.

  • How does the amplitude of the green wave change with the Bragg angle theta?

  • What influence does the distance between the two layers have on the diffracted(=green) wave ?

  • What influence does the wave length have on the diffracted(=green) wave ?

  • Under which conditions do you get the highest (lowest) amplitude of the diffracted(=green) wave ?

  • How high is the highest (lowest) amplitude of the diffracted(=green) wave ?

  • What influence does the horizontal position of the upper atom have on the diffracted(=green) wave ?

Once you are done, click here to verify your answers.
© Th. Proffen and R.B. Neder, 2003