This book revolves around questions rather than knowledge. It primarily addresses four questions, corresponding to four chapters: ① How were electromagnetic waves discovered? ② How do electromagnetic waves propagate and transmit? ③ How do electromagnetic waves radiate? ④ How do electromagnetic waves scatter? To thoroughly explain these four questions, this book encompasses various course knowledge, including existing electromagnetic wave theory, antennas, computational electromagnetics, and radar. It spans knowledge across undergraduate, postgraduate, and doctoral levels. This book does not aim to cover all knowledge points but strives to elucidate the core points and accurately reflect how these core points change with the times.