**Category:** Quantum Mechanics  
**Subtype:** Atomic Energy Levels and Photon Emission  
**Problem Description:** The problem involves calculating the number of emitted photons from a hydrogen atom when exposed to different frequencies of radiation. It starts with the energy levels of hydrogen atoms and how they transition between these levels when absorbing energy from incoming radiation. The goal is to determine how many photons are emitted when the atoms are exposed to a second frequency of radiation, given the behavior observed with the first frequency.