This book aims to provide a solid foundation in physics for students at an elementary level. Physics is crucial for comprehending the modern world and is an integral part of our culture. The book explores the forefront of physics research, examines the role of physics in society, and offers recommendations to enhance the field and its ability to address important needs. Furthermore, the book delves into the mathematical and numerical methods employed in electron emission. It explains the origins of these equations, their relationships, and how they can be applied accurately to model real-world sources for devices that utilize electron beams. The intention is to serve as an introductory reference on computational methods and techniques, targeting undergraduate students in science, mathematics, and engineering, typically at the sophomore or junior level.