Question 1

Q.1 Explain monopole and dipole antenna.

Accepted Answer

A monopole antenna is a single quarter-wave conductor fed against a ground plane, radiating into the upper hemisphere; a dipole antenna is two collinear quarter-wave arms fed at the centre, radiating a full doughnut-shaped pattern in free space.

Question 2

Q.2 Define attenuation in a waveguide.

Accepted Answer

Attenuation in a waveguide is the reduction in signal amplitude as a wave travels along the guide, arising below cutoff from evanescent (non-propagating) exponential decay, and above cutoff from finite conductor and dielectric losses.

Question 3

Q.3 Explain the advantage of a waveguide.

Accepted Answer

The advantages of a waveguide are very low loss (no centre conductor to add ohmic loss, fields largely confined in air), very high power-handling capacity, and immunity from radiation leakage, at the cost of bulk, rigidity, and a nonzero cutoff frequency.

Question 4

Q.4 Define total internal reflection.

Accepted Answer

Total internal reflection is the complete reflection of a wave at the interface between a denser and a rarer medium when the angle of incidence (from the denser side) exceeds the critical angle θc = sin⁻¹(n2/n1), with no power transmitted into the second medium.

Question 5

Q.5 Explain the term group velocity.

Accepted Answer

Group velocity vg = dω/dβ is the speed at which the envelope of a modulated wave packet (and hence energy/information) actually travels through a dispersive medium or waveguide, generally different from the phase velocity vp = ω/β.

Question 6

Q.6 Define radiation parameter importance.

Accepted Answer

Radiation parameters (gain, directivity, beamwidth, radiation resistance, polarization) are important because they quantify how efficiently and in which directions an antenna converts feed power into usable radiated electromagnetic energy, directly determining link range, coverage and interference performance of any wireless system.

Question 7

Q.7 Define boundary condition and its utility.

Accepted Answer

A boundary condition specifies how field components (tangential E, normal D, tangential H, normal B) relate across an interface between two media; its utility is enabling unique solution of Maxwell's equations in piecewise-homogeneous regions by fixing the constants of integration from the physics at each interface.

Question 8

Q.8 Explain the different applications of a transmission line.

Accepted Answer

Transmission lines are applied in power transmission/distribution, telecommunication signal transport (coax, twisted pair), RF/microwave interconnects between system components, and as distributed circuit elements (stubs, quarter-wave transformers, resonators, delay lines).

Question 9

Q.9 Explain the utility of a Smith chart.

Accepted Answer

The Smith chart's utility is to graphically compute reflection coefficient, VSWR, and impedance/admittance transformation along a line, and to design impedance-matching networks (stub, quarter-wave), without needing repeated complex-number arithmetic.

Question 10

Q.10 Explain the effect of characteristic impedance.

Accepted Answer

Characteristic impedance Z0 determines the ratio of voltage to current for a wave travelling in one direction on a line, and any mismatch between Z0 and the load impedance ZL causes partial reflection, standing waves, and reduced power transfer to the load.

Question 11

Q.1 Explain the method of antenna radiation for a Hertz dipole.

Accepted Answer

For a Hertz (infinitesimal) dipole of length dl carrying current I0, the retarded vector potential is evaluated along the dipole axis and differentiated to yield the near- and far-field E and H components, with the far-field radiation pattern sinθ and radiation resistance Rrad = 80π²(dl/λ)².

Question 12

Q.2 What is a uniform plane wave? Show that the field in the uniform plane wa…

Accepted Answer

A uniform plane wave is a wave whose E and H field magnitudes and phase are constant over any plane perpendicular to the propagation direction; substituting the plane-wave assumption ∂/∂x = ∂/∂y = 0 into Maxwell's equations shows the fields depend only on the propagation coordinate (z) and time, confirming independence from the two transverse dimensions.

Question 13

Q.3 What is the significance of Maxwell's equations? Mention them in their va…

Accepted Answer

Maxwell's equations unify all classical electromagnetism (electrostatics, magnetostatics, induction, and wave propagation) into four coupled equations; their significance is predicting the existence of self-propagating EM waves at speed c, and they exist in differential, integral, phasor, and free-space forms.

Question 14

Q.4 Discuss the different types of transmission lines and their applications.

Accepted Answer

Transmission line types include two-wire (parallel) lines, coaxial cable, microstrip/stripline, and waveguides, applied respectively in low-frequency open runs, shielded broadband/RF signal transport, planar RF/microwave circuit integration, and high-power low-loss microwave transmission.

Question 15

Q.5 For a transmission line which is terminated in normalized impedance Zn, V…

Accepted Answer

For VSWR = 2, the normalized load impedance magnitude at the point where the line presents a real (resistive) impedance ranges between 1/VSWR = 0.5 (at a voltage minimum) and VSWR = 2 (at a voltage maximum); in general |zn| depends on the specific reflection-coefficient phase, but its extreme (real-axis) values are set directly by VSWR.

Question 16

Q.6 Discuss the degenerate and dominant modes in a rectangular waveguide.

Accepted Answer

Degenerate modes are two or more distinct waveguide modes sharing exactly the same cutoff frequency (e.g., TEm0 vs TMm0-type coincidences, or TEmn/TMmn pairs with m,n≥1 in rectangular guide); the dominant mode is the single propagating mode with the lowest cutoff frequency of all modes the guide supports (TE10 for standard rectangular waveguide with a>b).

Question 17

Q.7 Derive an expression for the fields in a rectangular waveguide in the cas…

Accepted Answer

For TM modes in rectangular waveguide, Ez satisfies the Helmholtz equation with Ez=0 on all four walls (Dirichlet condition); solving by separation of variables gives Ez = E0 sin(mπx/a)sin(nπy/b)e^{−jβz}, from which all transverse field components (Ex, Ey, Hx, Hy) are derived via the standard TM field relations.

Question 18

Q.1 An air-filled rectangular waveguide of inside dimension 7 × 3.5 cm operat…

Accepted Answer

For a 7×3.5 cm air-filled waveguide in dominant TE10 mode: (i) fc = 2.143 GHz; (ii) at f = 3.5 GHz, vp ≈ 3.79×10⁸ m/s (≈1.265c); (iii) guided wavelength λg ≈ 10.84 cm.

Question 19

Q.2 (a) Describe the Smith chart and its application in analysis of a transmi…

Accepted Answer

(a) The Smith chart graphically maps normalized impedance to reflection coefficient for VSWR, matching and line-transformation calculations (detailed derivation given in Part C, Q.5 of the companion 2024 Main/Back paper); (b) for Z0=50+j0.01Ω, ZL=73−j42.5Ω: Γ≈0.274−j0.251 (|Γ|≈0.371), VSWR≈2.18.

Question 20

Q.3 (a) Explain the radiation solution for the potential function. [7] (b) Ex…

Accepted Answer

(a) The radiation solution for the potential function uses the retarded Green's function (μ/4π)(e^{−jkR}/R) to solve the inhomogeneous wave equation for A, giving the retarded vector potential integral (fully derived in Part C, Q.3 of the companion 2024 Main/Back paper); (b) the basic laws of electromagnetism are Coulomb's, Gauss's, Faraday's, and Ampere's (with Maxwell's displacement-current correction), unified into Maxwell's four equations.

Question 21

Q.4 (a) Explain the propagation of waves and their types. [7] (b) Explain wav…

Accepted Answer

(a) Waves propagate as transverse (TEM, TE, TM depending on boundary geometry), longitudinal (rare in EM, e.g. plasma oscillations), or surface/guided types, classified by field orientation relative to the propagation direction; (b) in a conducting medium the wave equation gives a complex propagation constant γ=α+jβ, from which phase velocity vp=ω/β and group velocity vg=dω/dβ are derived (full derivation given in Part C, Q.2 of the companion 2024 Main/Back paper).

Electromagnetics Waves