The terms "electromagnetic wave" and "electromagnetic field" are related but have distinct meanings:
Electromagnetic Wave: An electromagnetic wave refers to the propagation of oscillating electric and magnetic fields through space. It is a self-propagating disturbance that carries energy. Electromagnetic waves can travel through a vacuum or a medium and exhibit characteristics such as frequency, wavelength, and polarization. Examples of electromagnetic waves include radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. These waves are categorized based on their frequency or wavelength.
Electromagnetic Field: An electromagnetic field, also known as an EM field, refers to the region of space surrounding an electrically charged object or a current-carrying conductor. When a charge or a current is present, it generates an electromagnetic field. The electromagnetic field consists of both electric and magnetic components, which are interconnected and vary in strength and direction with respect to each other. The field exists even when it is not propagating as a wave. It is a fundamental concept in physics used to describe the interaction between electric charges and magnetic fields.
In summary, an electromagnetic wave is the result of the oscillation of electric and magnetic fields that propagate through space, carrying energy. On the other hand, an electromagnetic field represents the presence of electric and magnetic fields in a given region, regardless of whether there is a propagating wave. Electromagnetic waves are a manifestation of the electromagnetic field when it is in a state of propagation.