Question

An electromagnetic wave radiates outwards from a dipole antenna with${E_0}$ as the amplitude of its electric field vector. The electric field ${E_o}$ which transports significant energy from the source falls off as
(A) $\dfrac{1}{{{r^3}}}$
(B) $\dfrac{1}{{{r^2}}}$
(C) $\dfrac{1}{r}$
(D) Remains constant.

Answer 1

Hint: Electric field strength is a quantitative expression of the intensity of an electric field at a particular point. SI unit is volt per meter which means that the field strength of one volt per meter represents a potential difference of one volt between the points separated by one meter. Any electrically charged object has the ability to produce an electric charge. Electric field strength is defined in terms of linear displacement instead of using surface area.

Complete step by step solution:
Since the electromagnetic waves fall outwards the amplitude of the electric field vector which carries energy from the source falls intensity inversely as the distance from the antenna.
$E = \dfrac{V}{r}$
Where V is the potential difference
Since the energy is constant E is inversely proportional to r.

So the correct answer is option C.

Additional information: EM waves which are basically electromagnetic waves are the waves which are created due to the vibrations between magnetic and electric fields, hence we can say that EM waves are the waves that are produced as a result of oscillating magnetic and electric fields. These magnetic and electric fields are perpendicular to each other. These both fields which are created by the charged particle are self-perpetuating-time dependent.

Note: EM waves are measured by their magnitude and wavelength hence they are transverse waves. Lowest point is referred to as the trough and the highest point is called the crest. Various types of EM waves are X-rays, gamma rays, IR waves, radio waves, microwaves, UV rays and optical rays.