This chapter discusses light and matter, including key topics such as: - Electromagnetic waves are created by accelerating charges and can transmit energy through space without a medium. - The electromagnetic spectrum encompasses radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. - Spectroscopy techniques allow analysis of spectra to identify elements and temperatures of objects. - Atomic structure explains the formation of spectral lines through electron transitions between energy levels. - The Doppler effect alters the perceived frequency of light based on relative motion between the source and observer.