Transverse-magnetic (TM) Mode

When a particular mode is excited in a waveguide, an extra electric component appears in the direction of propagation. This resulting mode is known as the transverse-magnetic (TM) mode. Let's delve into the details of this phenomenon.

Waveguides and Modes

A waveguide is a structure that guides electromagnetic waves along a specific path. It is usually made of a metallic material and has a hollow interior. Waveguides are used to transmit and control electromagnetic signals in various applications.

Modes in a waveguide refer to the possible ways in which an electromagnetic wave can propagate through it. Each mode has a specific distribution of electric and magnetic fields within the waveguide. The mode with the lowest cutoff frequency is called the fundamental mode.

Transverse-Electric (TE) and Transverse-Magnetic (TM) Modes

In the transverse-electric (TE) mode, the electric field is perpendicular to both the direction of propagation and the walls of the waveguide. This means that there is no electric field component in the direction of propagation.

In the transverse-magnetic (TM) mode, the magnetic field is perpendicular to both the direction of propagation and the walls of the waveguide. In this mode, an extra electric field component appears in the direction of propagation. This additional electric field component is known as the longitudinal electric field.

Understanding the Resulting TM Mode

When a particular mode is excited in a waveguide, the resulting mode can be determined by analyzing the electric and magnetic field distributions within the waveguide. For the given scenario, since an extra electric component appears in the direction of propagation, it indicates the presence of the transverse-magnetic (TM) mode.

The longitudinal electric field in the TM mode contributes to the wave propagation and carries energy along the waveguide. It is important to note that in the TM mode, the magnetic field remains perpendicular to both the direction of propagation and the walls of the waveguide.

Therefore, the correct answer to the question is option 'B' - transverse-magnetic (TM) mode.

In Conclusion

When a particular mode is excited in a waveguide, the resulting mode can be determined by analyzing the electric and magnetic field distributions within the waveguide. In the case where an extra electric component appears in the direction of propagation, it indicates the presence of the transverse-magnetic (TM) mode. This mode is characterized by a perpendicular magnetic field and an additional longitudinal electric field component.