Astronomy clicker question: photon energy requirement

Astronomy 210, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

Students were asked the following clicker question (Classroom Performance System, einstruction.com) at the end of their learning cycle:

A photon with slightly more energy than is required for an electron to move between energy levels 1 -> 2 would:
(A) be absorbed, causing the electron to move between energy levels 1 -> 2.
(B) not be absorbed, such that the electron stays in energy level 1.
(C) (Not enough information is given to answer this.)
(D) (I'm lost, and don't know how to answer this.)

Section 30674 (pre-)
(A) : 17 students
(B) : 10 students
(C) : 4 students
(D) : 0 students

This question was asked again after displaying the tallied results with the lack of consensus, with the following results. No comments were made by the instructor, in order to see if students were going to be able to discuss and determine the correct answer among themselves.

Section 30674 (post-)
(A) : 12 students
(B) : 17 students
(C) : 2 students
(D) : 0 students

Correct answer: (B)

A photon must have exactly the right amount of energy in order to be absorbed by an electron and cause the electron to make an orbital transition. "No more, no less."

Some students persistent in believing that an electron could absorb a photon with more than enough energy required. However in the quantum world: "Exact change only."

Pre- to post- peer-interaction gains:
pre-interaction correct = 32%
post-interaction correct = 55%
Hake (normalized) gain <g> = 33%