Physics 102
Practice Exam Problem #14

An astronomer observes the Orion nebula through a telescope and passes the light from Orion through a prism. This reveals a spectrum showing several emission lines including the Balmer lines that correspond to transitions from the 3rd, 4th and 5th energy levels to the n=2 level.

(a) Make a sketch of the Bohr atom energy levels, showing these transitions.

(b) Calculate the wavelengths and energies for these transitions. (The Rydberg constant is given on the cover of the exam to be R=1.097E7/m; Planck's constant and the speed of light are also given.)

(c) What is the energy of the n=2 to n=1 transition for hydrogen? Why is the astronomer not seeing this transition in the spectrum?

(Problem from an actual former Physics 102 exam)
Solution

Physics 102 HW page