**Kazuhiro Hirasawa**

Emeritus Professor, University of Tsukuba, Japan

**1**

Section 1

Introduction

Section 1 Introduction

**3**

**Chapter 1**

**1. Introduction**

nucleus.

charged particles.

protons and electrons.

fields being coupled together.

transverse electromagnetic or TEM wave.

tional force attracts any object with mass.

Introductory Chapter:

Electromagnetism

*Kim Ho Yeap and Kazuhiro Hirasawa*

There are four fundamental forces in nature, namely:

(ii) The electromagnetic force which is in the order of 10<sup>−</sup><sup>2</sup>

(i) The strong nuclear force is the strongest among the four forces. The strong force is known to bind subatomic particles (such as protons and neutrons) to form

force [1]. The electromagnetic force governs the interactions among electrically

(iii) The weak nuclear force which is in the order of 10<sup>−</sup>14 of the strong force [1]. The weak force acts in each individual nucleons (i.e., collections of protons and neutrons) and is responsible for the radioactive decay when neutrons decay to

(iv) The gravitational force which is the weakest among all forces. The gravita-

A field is a spatial distribution of quantity, which may or may not be a function of time [2]. To put it in simple terms, an electromagnetic field is basically the field produced as a consequence of positively and/or negatively charged particles, be at rest or in motion, and exerted forces among each other. The electromagnetic field consists of both the electric field and the magnetic field. During static condition, both electric and magnetic fields exist independently. When only an electric field is present and is constant in time, the field is known as an electrostatic field; similarly, when only a constant magnetic field is present, it is known as a magnetostatic field. When the fields change over time (i.e., in time-varying condition), however, both fields have to be concurrently present. This is to say that a time-varying electric field induces a time-varying magnetic field and vice versa [1], resulting in both

Due to its particle-wave duality nature, an electromagnetic field can be viewed as a continuous field which propagates in a wavelike manner, while at the same time, it can also be seen as quantized particles called photons. When the wave of the electromagnetic field propagates in an isotropic homogeneous medium, the electric and magnetic field components are mutually transverse to the direction of the energy transfer, as depicted in **Figure 1**. The radiation is therefore known as a

that of the strong
