Light is composed of electric and magnetic fields and thus its alternate name "electromagnetic spectrum". Light can be absorbed and emitted by atoms and molecules. The precise details of which give us the world we see around us.
The equations of modern atomic theory are difficult to solve. Fortunately, many of the results can be obatined by following some simple rules. These rules are known as the Aufbau principle.
According to the physics of the time, Rutherford's planetary atom should have an extremely short lifetime. Bohr thought about the problem and knew of the emission spectrum of hydrogen. He quickly realized that the two problems were connected and after some thought came up with the Bohr model of the atom. Bohr's model of the atom revolutionized atomic physics.
Interactive - students can check answers. Great for student understanding. Unfortunately sometimes names get cut short. Have talked to developer - its a mac glitch he does not know how to fix :( Still use it anyway....