A dipole antenna is located at the origin with its axis...

A dipole antenna is located at the origin with its axis along the $z$ -axis. As electric current oscillates up and down the antenna, polarized electromagnetic radiation travels away from the antenna along the positive $y$ -axis. What are the possible directions of electric and magnetic fields at point $A$ on the $y$ -axis? Explain.

Key Concepts

Electromagnetic Wave Propagation

Electromagnetic waves are transverse waves where the oscillations of the electric and magnetic fields occur perpendicular to the direction in which the wave travels. This means that at any given point in space, the electric field, magnetic field, and the wave’s propagation vector form a set of mutually orthogonal directions.

Field Orthogonality in Electromagnetic Waves

In any electromagnetic wave, the electric and magnetic fields are oriented at right angles to one another and to the direction of propagation. This inherent orthogonality leads to the result that knowing one field’s orientation can be used to determine the other through simple vector relationships, such as the cross product between the fields.

Dipole Antenna Radiation Pattern

A dipole antenna radiates electromagnetic waves primarily in a direction perpendicular to its axis. The overall pattern of radiation depends on the geometry and orientation of the antenna, with maximum radiation occurring in the plane normal to the antenna’s length and nulls along the direction of the dipole axis.

Polarization of Electromagnetic Waves

Polarization describes the orientation of the electric field vector in an electromagnetic wave. It is a key property that defines the wave’s transverse oscillations and is determined by the setup of the source, such as the alignment of a dipole antenna, which sets the fundamental direction of the electric field.

Right-Hand Rule in Electromagnetics

The right-hand rule is a mnemonic used to determine the relationships between the directions of the electric field, magnetic field, and the propagation vector in electromagnetic waves. By aligning the fingers of the right hand in the direction of the electric field and curling them towards the magnetic field, the thumb then points in the direction of wave propagation, encapsulating the inherent cross-product relationship.

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