The fourth book in the series of Understanding Physics describes three important topics. Fluids – which include both liquids and gases – play a central role in our daily lives. We breathe and drink them, and a rather vital fluid circulates in the human cardiovascular system. The Earth's oceans and atmosphere consist of fluids. Waves – deals with many phenomena like sound waves that carry our messages from our vocal cords to the ears of our friends. Electromagnetic waves carried through optic fibers or through the atmosphere, allow communication with satellites. The book presents: oscillations and harmonic motions, mechanical waves and sound waves. Thermodynamics – heat theory development is one of humankind's most profound intellectual achievements. Understanding thermodynamic principles was fundamental for steam engines that powered the industrial revolution. The book deals with the first law of the thermodynamics, the kinetic theory of gases and the second law of thermodynamics. As in former volumes of Understanding Physics – this book contains clear explanations from basics phenomena to complicated models. It allows readers to examine their understanding by reading exercises and examples. Many figures, diagrams and photos facilitate discovery with this book and convert the experience of learning into a vivid and plausible encounter. The book is based on Fundamental of Physics by David Halliday, Robert Resnick and Jearl Walker.

Magnetism and Optics is a second book in the series of three. This book is built on the foundations of the 6th Edition of Halliday, Resnick, and Walker’s Fundamentals of Physics. One of primary goals of this book is to help students make sense of the physics they are learning. We cannot achieve this goal if students see physics as a set of disconnected mathematical equations that each apply only to a small number of specific situations. We stress conceptual and qualitative understanding and continually make connections between mathematical equations and conceptual ideas. We also try to build on ideas that students can be expected to already understand, based on the resources they bring from everyday experiences. This text is designed to work with learning strategies such as microcomputer-based labs and interactive lectures that are increasingly being used in physics instruction.