With an emphasis on numerical modelling, Physics of the Sun: A First Course presents a quantitative examination of the physical structure of the Sun and the conditions of its extended atmosphere. It gives step-by-step instructions for calculating the numerical values of various physical quantities in different regions of the Sun. Fully updated throughout, with the latest results in solar physics, this second edition covers a wide range of topics on the Sun and stellar astrophysics, including the structure of the Sun, solar radiation, the solar atmosphere, and Sun-space interactions. It explores how the physical conditions in the visible surface of the Sun are determined by the opacity of the material in the atmosphere. It also presents the empirical properties of convection in the Sun, discusses the physical conditions which must be satisfied for nuclear reactions to occur in the core, and describes how radiation transports energy from the core outwards. This text enables a practical appreciation of the physical models of solar processes. Numerical modelling problems and step-by-step instructions are featured throughout, to empower students to calculate, using their own codes, the interior structure of different parts of the Sun and the frequencies of p-modes and g-modes. They encourage a firm grasp of the numerical values of actual physical parameters as a function of radial location in the Sun. It is an ideal introduction to solar physics for advanced undergraduate and graduate students in physics and astronomy, in addition to research professionals looking to incorporate modelling into their practises. Extensive bibliographies at the end of each chapter enable the reader to explore the latest research articles in the field. Features: Fully updated with the latest results from the spacecraft Hinode, Stereo, Solar Dynamics Observatory (SDO), Interface Region Imaging Spectrograph (IRIS), and Parker Solar Probe Presents step-by-step explanations for calculating numerical models of the photosphere, convection zone, and radiative interior with exercises and simulation problems to test learning Describes the structure of polytropic spheres and the acoustic power in the Sun and the process of thermal conduction in different physical conditions