Optics has been part of scientific enquiry from its beginning and remains a key element of modern science. This book provides a concise treatment of physical optics starting with a brief summary of geometrical optics. Scalar diffraction theory is introduced to describe wave propagation and diffraction effects and provides the basis for Fourier methods for treating more complex diffraction problems. The rest of the book treats the physics underlying some important instruments for spectral analysis and optical metrology, reflection and transmission at dielectric surfaces and the polarization of light. This undergraduate-level text aims to aid understanding of optical applications in physical, engineering and life sciences or more advanced topics in modern optics.