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The correct choice is (B) 200

The EXPLANATION: The number of MODES in a waveguide is given by m = V^2/2. On substituting for V = 20, we get m = 400/2 = 200 modes.

Right CHOICE is (c) H is transverse to wave direction

Easiest EXPLANATION: In transverse MAGNETIC WAVES, the magnetic field strength is transverse to the wave direction. They are also called E waves.

Correct CHOICE is (a) Phase CONSTANT α ω

Easiest EXPLANATION: The phase constant is given by β = ω√LC. THUS the relation is β is directly PROPORTIONAL to ω.

The correct choice is (a) 2.88 GHZ

The EXPLANATION: The cut off frequency of a TE WAVE in any other MEDIUM is mc/2a√εr. On substituting for a = 0.035 and εr = 2.2, we get the cut off frequency as 2.88 GHz.

Correct choice is (d) COMPLEX and equal to phase constant

The best I can EXPLAIN: The PROPAGATION constant is GIVEN by γ = α + jβ, where α and β are the attenuation and phase constants RESPECTIVELY. For a lossless line, the attenuation constant is zero. Thus γ = jβ. It is clear that γ is complex and equal to β.

Correct option is (c) 1

Explanation: The attenuation of a wave is given by α = R/2Z0. On substituting for R = 100 and Z0 = 50, we get α = 100/(2 X 50) = 1 unit.

Right choice is (d) 5 GHz

For explanation: The cut off FREQUENCY in dominant mode will be fc = mc/2a. On substituting for c = 3 x 10^8 and a = 0.03, we get the cut off frequency as 5 GHz.

Correct OPTION is (a) Dominant mode

To EXPLAIN: Dominant modes are the modes having LEAST cut off frequency. This implies they have highest cut off WAVELENGTH.

Right answer is (a) 628.33

For EXPLANATION: The intrinsic impedance of a TE wave is GIVEN by ηTE = η/cos θ, where cos θ is given by √(1- (fc/f)^2). On SUBSTITUTING for fc = 6 GHz, f = 7.5 GHz and η = 377, we get the intrinsic impedance as 628.33 units.

The correct ANSWER is (B) No

For EXPLANATION: For a waveguide, the DIMENSION a should be greater than b. Here a = 3 and b = 5.5, thus such waveguide does not exist.

Correct CHOICE is (c) E is transverse to WAVE direction

Best explanation: In TE waves, the electric field strength will be transverse to the wave direction. THUS the TE waves are also CALLED H waves.

The correct OPTION is (a) Increasing TRANSMISSION coefficient

To EXPLAIN I would say: The WAVEGUIDES are used to increase the transmission efficiency of the waves TRAVELLING through it.

Correct option is (b) 4

To ELABORATE: The cut off WAVELENGTH of a waveguide is GIVEN by λc = 2a/m. For the dominant MODE, m = 1. Given that λc = 2, thus we get a = 4 units.

The correct option is (a) Yes

Easiest EXPLANATION: The CUT off FREQUENCY for waveguide operation is 6 GHZ. Thus a wave of 5 GHz is not possible for transmission in a waveguide.

Right option is (c) Cut off FREQUENCY to frequency

The BEST EXPLANATION: The ratio of the cut off frequency to the frequency at any point gives the SIN θ in a WAVEGUIDE.

Correct option is (d) nc/2b

To explain: The CUT off frequency CONSISTS of modes m and n. For m = 0, the DIMENSION B will be CONSIDERED. Thus the frequency is nc/2b, where c is the speed of the light.

The CORRECT answer is (a) 0.1

Easiest explanation: The cut off wavelength of the waveguide is given by λc = 2a/m. on substituting for a = 0.05 and m = 1, we get λc = 2 x 0.05/1 = 0.1 UNITS.

The CORRECT answer is (B) a > b

Explanation: The dimensions a and b represent the BROAD wall and the side wall dimensions respectively. The broad wall will be greater than the side wall. Thus the CONDITION a>b is true.

Correct choice is (c) 7.5

Easy EXPLANATION: The phase velocity of a WAVE is GIVEN by Vp = ω/βg. on SUBSTITUTING for ω = 15 and βg = 2, we GET phase velocity as 15/2 = 7.5 units.

Right option is (d) 6 GHz

The BEST I can explain: The dominant mode in TE is TE10. The CUT off frequency will be mc/2a, where m = 1 and a = 0.025 are GIVEN. On substituting, we get the frequency as 1 x 3 x 10^8/2 x 0.025 = 6 GHz.

The CORRECT OPTION is (a) ω√(LC)

For explanation: The phase CONSTANT of a wave in a transmission line is given by β = ω√(LC), where L and C are the specifications of the line.

Right answer is (a) Attenuation constant

Easiest EXPLANATION: The propagation constant is given by γ = α + jβ. Here the real part is the attenuation constant and the imaginary part is the PHASE constant.

Correct answer is (C) 200

Easiest EXPLANATION: The RELATION between the MODES and the V number is given by m = v^2/2. Given that v = 20, we get m = 20^2/2 = 200 modes.

The correct ANSWER is (d) 1

The explanation is: The group wavelength is given by λg = 2π/βg, where βg is the group wavelength of the WAVE. On substituting for βg = 6.28, we GET group wavelength as UNITY.

Right ANSWER is (B) Broad WALL and SIDE wall dimension respectively

Easiest explanation: In rectangular waveguide, the a parameter is the broad wall dimension of the waveguide and the b parameter is the side wall dimension of the waveguide. Always, a > b in a waveguide.

Correct option is (d) 6 GHz

The explanation is: The CUT off frequency of the WAVEGUIDE is 6 GHz. This is the frequency at which the waveguide will start to OPERATE.

Right choice is (d) GHZ

Easy explanation: WAVEGUIDES are employed for effective TRANSMISSION, when the LINES carry ELECTROMAGNETIC waves in the GHz range.

Right choice is (a) True

The explanation is: In a scattering matrix, the PARAMETERS S11 and S22 INDICATE the transmission coefficients and the parameters S21 and S12 indicate the reflection coefficients.

Right option is (a) Low bulk resistivity

To EXPLAIN I WOULD SAY: Generally, the waveguides are made of materials with low bulk resistivity like brass, copper, SILVER etc. But if the interior walls are properly plated, it is possible with poor conductivity materials too. It is even possible to make plastic waveguides.

Correct option is (b) 0

The explanation is: The PARAMETERS S12 and S21 are the reflection coefficients. For a MATCHED LINE, the reflection coefficients are zero. Thus the parameters S12 and S21 are also zero.

The CORRECT ANSWER is (a) H parameter model

For explanation: The T, ABCD and S parameter models are USED in the transmission line modelling. The h parameter is not used for the same.

Correct answer is (b) HIGHEST wavelength

For explanation: The dominant mode is the mode which has the MINIMUM FREQUENCY or MAXIMUM wavelength available for propagation of the waves.

The correct choice is (c) Total internal reflection

Easiest explanation: The WAVEGUIDES use total internal reflection phenomenon to TRANSMIT the WAVES passing through it. THUS the acceptance angle and critical angle are important for effective TRANSMISSION.