Rutherford Scattering

In the early 20th century, quite a bit less was known about the structure of the atom. Several ideas were proposed, including the plum pudding model, which suggested that particles were distributed uniformly throughout the atom.

Rutherford Scattering is a Java-based simulation that lets you run a couple of experiments which show how the plum pudding model was disproved. As the name suggests, it highlights Rutherford scattering, which occurs when particles encounter the dense nucleus of an atom.

At a time when little was understood about the nature of the universe at a microscopic scale, the leading theory was that electrons were distributed uniformly in a region of space that was positively charged (the pudding).

For this theory to be true, alpha particles fired at the atom should either pass through unaffected or only be deflected slightly.

What Ernest Rutherford observed, however, was that particles were deflected at large angles, sometimes even being turned around. This would only be possible if the atom’s mass were concentrated in a very small area, which contradicted the plum pudding model.

With this program, you can fire alpha particles at an atom’s nucleus and observe how their trajectories are deflected when getting close to it. You can also modify their energy, as well as the number of protons and neutrons in the nucleus.

The second simulation shows how the results would likely have looked if the atom’s mass were spread out over a larger area. The alpha particles would pass through and maintain their trajectories.

Rutherford Scattering is an interesting simulation that can help physics teachers explain this phenomenon more intuitively. It is easy to use and only requires Java to be installed on your computer.