Introduction to Modern Physics — Chapter 6: Atomic spectra

About this lesson

This unit introduces modern physics concepts, starting with Bohr's model of the hydrogen atom and the emission of light. It explains how electrons in hydrogen atoms are excited to higher energy levels and then emit photons when returning to lower levels, producing line spectra. The unit details the five spectral series (Lyman, Balmer, Paschen, Brackett, and Pfund) and their locations in the electromagnetic spectrum. It also covers the use of a spectrometer to obtain pure spectra and distinguishes between continuous, line, emission, and absorption spectra, with examples like Fraunhofer lines. The unit then moves to X-rays, describing their properties, production in a Coolidge tube, and the two types of X-ray spectra (continuous and characteristic). It explains the mechanisms behind each type and lists applications such as studying crystal structures and medical imaging. Finally, the unit introduces lasers, explaining the concepts of spontaneous and stimulated emission, and how stimulated emission leads to coherent, collimated light.