The Pfund series results from emission/absorption of photons due to transitions of electrons in a hydrogen to/from the n=5 energy level from/to higher energy levels.What is the longest wavelength photon emitted in the Pfund series?
A)658 nm
B)2.29 µm
C)2.74 µm
D)7.47 µm
E)12.4 µm

Question

Quizplus · Accepted Answer

The Pfund series involves transitions from higher energy levels to n=5. Therefore, it corresponds to infrared wavelengths. The longest wavelength photon emitted corresponds to the transition from n=∞ to n=5, which is known as the Pfund limit. Using the formula for the wavelength of a photon emitted from a transition between two energy levels in hydrogen:

1/λ=R(1/52−1/n2)

where R is the Rydberg constant, we can calculate the wavelength of the photon emitted in the Pfund limit as:

1/λ=R(1/52−1/∞2)=R/25

Substituting the value of the Rydberg constant and converting to micrometers gives:

λ=1/(R/25) micrometers=7.47 µm

Therefore, the longest wavelength photon emitted in the Pfund series is option D) 7.47 µm.

The Pfund Series Results from Emission/absorption of Photons Due to Transitions