This is a first course on quantum mechanics and describes simple applications to physical phenomena that are of immediate and everyday interest. The first five chapters introduce the fundamentals of quantum mechanics and are followed by a quiz so readers can test themselves. The remaining chapters describe applications, including the physics of lasers, molecular binding, simple properties of crystalline solids arising from their band structure, and the operation of junction transistors. This new expanded edition now includes a chapter on the theory of spin and its application to magnetic resonance imaging, as well as a description of the WKB approximation and its application to alpha decay. Ideal either as a course text or a self-study text, the book contains nearly 100 exercises and hints to their solution.