A hydrogen atom initially in an excited state emits two photons as it returns to the…
PHYSICS · Single correct · A Level · Physics · Particles and radiation · Particles and radiation
Problem
A hydrogen atom initially in an excited state emits two photons as it returns to the ground state. Photon X has wavelength 121nm and photon Y has wavelength 656nm. Which of the following best explains why photon X carries more energy than photon Y?
(a) Photon X involves the electron dropping two principal quantum levels instead of one, and a larger change in n always releases more energy.
(b) Photon X corresponds to a transition that ends at the first energy level, so the energy difference between the two states is larger.
(c) Photon X has a shorter wavelength, and since photon energy is directly proportional to wavelength (E∝λ), it must carry more energy than photon Y.
(d) Photon X is emitted first in the cascade, and the first photon released always carries the greatest energy.