30. Bohr Atom

When introducing the Bohr atom it is a good idea to review standing waves for the students, for example with Rudnick's String. You can show how the string resonates for various harmonics as the driving frequency is changed.

Another demonstration puts standing waves on a circular wire loop - standing waves around a circle. A mechanical wave driver controlled by a function generator shakes the loop at the bottom and it resonates with an odd number of antinodes on the circle at the frequencies:

Number of antinodes Frequency (Hz)
3 18
5 65
7 140
9 237