Quantum Mechanics Solution Manual 

© Leon van Dommelen 

4.3.3.3 Solution hydcc
Question:
Based on the results of the previous question, what is the color of the light emitted in a Balmer transition from energy to ? The PlanckEinstein relation says that the angular frequency of the emitted photon is its energy divided by , and the wave length of light is where is the speed of light. Typical wave lengths of visible light are: violet 400 nm, indigo 445 nm, blue 475 nm, green 510 nm, yellow 570 nm, orange 590 nm, red 650 nm.
Answer:
The energy carried away by the photon is the energy lost by the electron, which is
Dividing by 1.054 10 J s gives the angular frequency to be 2.87 10/s, and then the wave length is 656 nm, using 3 10 m/s. That will be red light.