# Multiple choice question for engineering

## Set 1

1. The waveguide is employed in the transmission lines, when operated at the range of

a) Hz

b) KHz

c) MHz

d) GHz

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2. The cut off frequency for a waveguide to operate is

a) 3 MHz

b) 3 GHz

c) 6 MHz

d) 6 GHz

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3. In rectangular waveguides, the dimensions a and b represent the

a) Broad wall dimensions

b) Broad wall and side wall dimension respectively

c) Side wall and broad wall dimension respectively

d) Side wall dimensions

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4. The Bessel function is denoted by

a) J_{n}(ha)

b) J_{m}(ha)

c) J_{n}(hb)

d) J_{m}(hb)

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_{n}(ha) = 0. Here n is the order of the Bessel function.

5. In a waveguide, always which condition holds good?

a) phase velocity = c

b) phase velocity greater than c

c) phase velocity lesser than c

d) group velocity = c

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6. The group wavelength is greater than the wavelength at any point. State true/false.

a) True

b) False

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7. Find the group wavelength of a wave, given that the group phase constant is 6.28 units.

a) 2

b) 3.14

c) 6.28

d) 1

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8. The phase velocity of a wave with frequency of 15 radian/sec and group phase constant of 2 units is

a) 30

b) 15

c) 7.5

d) 2/15

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9. The modes in a material having a V number of 20 is

a) 20

b) 400

c) 200

d) 100

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^{2}/2. Given that v = 20, we get m = 20

^{2}/2 = 200 modes.

10. The number of modes is given as 50, find the V number.

a) 5

b) 10

c) 50

d) 2500

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^{2}/2. Given that m = 50, we get v

^{2}= 2 x 50 = 100. The V number is 10.

## Set 2

1. The reflection coefficient of a wave with transmission coefficient 0.35 is

a) 1.35

b) 0.65

c) 0.35

d) 0.7

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2. The incident wave amplitude is 24 units. Find the reflected wave amplitude if the reflection coefficient is 0.6.

a) 14.4

b) 16.6

c) 13.3

d) 11.1

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3. Find the reflection coefficient of the wave passing through two media having intrinsic impedances of 4 and 9 respectively.

a) 0.5

b) 1

c) 0.38

d) 0.1

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4. The reflection coefficient of a wave travelling through two media having permittivities 4 and 9 respectively is

a) 0

b) 0.5

c) 0.25

d) 0.2

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5. Calculate the transmission coefficient, when the incident and transmitted amplitudes are 10 and 7 respectively.

a) 17

b) 3

c) 10/7

d) 0.7

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6. The transmission coefficient in a wave travelling through two media having intrinsic impedances of 5.5 and 1.33 is

a) 0.389

b) 0.55

c) 0.133

d) 0.42

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7. The transmission coefficient in a wave travelling through two media having permittivities 4 and 1 is

a) 1/4

b) 3/2

c) 3/4

d) 2/3

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8. The reflection coefficient of a transmission line having characteristic and load impedances as 50 and 30 ohm respectively is

a) 1/4

b) 1/8

c) 1/2

d) 3/4

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9. In matched line, the transmission coefficient is

a) 0

b) 1

c) -1

d) Infinity

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10. Find the power reflected in a transmission line, when the reflection coefficient and input power are 0.45 and 18V respectively.

a) 3.645

b) 6.453

c) 4.563

d) 5.463

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^{2}Pinc. On substituting for R = 0.45 and Pinc = 18, we get Prefl = 0.45

^{2}x 18 = 3.645 units.

11. The transmitted power in a transmission line, when the reflection coefficient and the incident power are 0.6 and 24V respectively, is

a) 15.36

b) 51.63

c) 15.63

d) 51.36

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^{2})Pinc, where R = 0.6 and Pinc = 24, from the given data. Thus Ptr = (1- 0.6

^{2}) x 24 = 15.36 units.

12. The reflection coefficient of a short circuit transmission line is -1. State True/False.

a) True

b) False

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## Set 3

1. The Snell’s law can be derived from which type of incidence?

a) Incidence angle

b) Reflected angle

c) Refracted angle

d) Oblique incidence

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2. The Snell’s law is given by

a) N1 sin θi = N2 sin θt

b) N2 sin θi = N1 sin θt

c) sin θi = sin θt

d) N1 cos θi = N2 cos θt

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3. Calculate the ratio of sine of incident angle to the sine of reflected angle when the refractive indices of medium 1 and 2 are given as 2.33 and 1.66 respectively.

a) 0.71

b) 1.4

c) 2

d) 3.99

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4. Find the ratio of the refractive index of medium 1 to that of medium 2, when the incident and reflected angles are given by 300 and 450 respectively.

a) 0.5

b) 1

c) 2

d) 4

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5. The refractive index of a medium with permittivity of 2 and permeability of 3 is given by

a) 3.56

b) 2.45

c) 3.21

d) 1.78

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^{8}√(2 x 4π x 10

^{-7}x 3 x 8.854 x 10

^{-12}) = 2.45.

6. The critical angle is defined as the angle of incidence at which the total internal reflection starts to occur. State True/False.

a) True

b) False

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7. The critical angle for two media of refractive indices of medium 1 and 2 given by 2 and 1 respectively is

a) 0

b) 30

c) 45

d) 60

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^{-1}(n2/n1) = sin

^{-1}(1/2) = 30 degree.

8. The critical angle for two media with permittivities of 16 and 9 respectively is

a) 48.59

b) 54.34

c) 60

d) 45

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^{-1}(3/4) = 48.59 degree.

9. The angle of incidence is equal to the angle of reflection for perfect reflection. State True/False.

a) True

b) False

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10. The angle of incidence of a wave of a wave with angle of transmission 45 degree and the refractive indices of the two media given by 2 and 1.3 is

a) 41.68

b) 61.86

c) 12.23

d) 27.89

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^{-1}(1.3 sin 45)/2 = 41.68 degree.

11. The angle at which the wave must be transmitted in air media if the angle of reflection is 45 degree is

a) 45

b) 30

c) 60

d) 90

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12. For a critical angle of 60 degree and the refractive index of the first medium is 1.732, the refractive index of the second medium is

a) 1

b) 1.5

c) 2

d) 1.66

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## Set 4

1. In a transverse electric magnetic wave, which of the following will be true?

a) E is transverse to H

b) E is transverse to wave direction

c) H is transverse to wave direction

d) E and H are transverse to wave direction

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2. The cut off frequency of the TEM wave is

a) 0

b) 1 GHz

c) 6 GHz

d) infinity

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3. Which component is non zero in a TEM wave?

a) Ex

b) Hz

c) Ez

d) Attenuation constant

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4. TEM wave can propagate in rectangular waveguides. State true/false.

a) True

b) False

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5. The cut off wavelength in the TEM wave will be

a) 0

b) Negative

c) Infinity

d) 1/6 GHz

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6. The guided wavelength of a TEM wave in a waveguide having a wavelength of 5 units is

a) 0

b) Infinity

c) 5

d) 1/5

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7. The guided phase constant of a TEM wave in a waveguide with a phase constant of 2.8 units is

a) 2.8

b) 1.4

c) 0

d) Infinity

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8. Which type of transmission line accepts the TEM wave?

a) Copper cables

b) Coaxial cable

c) Rectangular waveguides

d) Circular waveguides

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9. For a TEM wave to propagate in a medium, the medium has to be

a) Air

b) Insulator

c) Dispersive

d) Non dispersive

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10. Stripline and parallel plate waveguides support the TEM wave. State true/false.

a) True

b) False

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## Set 5

1. When the phase angle between the Ex and Ey component is 0^{0} or 180^{0}, the polarisation is

a) Elliptical

b) Circular

c) Linear

d) Perpendicular

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^{0}and 180

^{0}for linearly polarised wave. The wave is assumed to be propagating in the z direction.

2. The magnitude of the Ex and Ey components are same in which type of polarisation?

a) Linear

b) Circular

c) Elliptical

d) Perpendicular

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3. When the Ex and Ey components of a wave are not same, the polarisation will be

a) Linear

b) Elliptical

c) Circular

d) Parallel

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4. Identify the polarisation of the wave given, Ex = Exo cos wt and Ey = Eyo sin wt. The phase difference is +90^{0}.

a) Left hand circularly polarised

b) Right hand circularly polarised

c) Left hand elliptically polarised

d) Right hand elliptically polarised

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5. Identify the polarisation of the wave given, Ex = 2 cos wt and Ey = sin wt. The phase difference is -90^{0}.

a) Left hand circularly polarised

b) Right hand circularly polarised

c) Left hand elliptically polarised

d) Right hand elliptically polarised

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6. Identify the polarisation of the wave given, Ex = 2 cos wt and Ey = 2 sin wt. The phase difference is +90^{0}.

a) Left hand circularly polarised

b) Right hand circularly polarised

c) Left hand elliptically polarised

d) Right hand elliptically polarised

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7. Identify the polarisation of the wave given, Ex = cos wt and Ey = sin wt. The phase difference is -90^{0}.

a) Left hand circularly polarised

b) Right hand circularly polarised

c) Left hand elliptically polarised

d) Right hand elliptically polarised

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8. For a non-zero Ex component and zero Ey component, the polarisation is

a) Parallel

b) Perpendicular

c) Elliptical

d) Circular

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9. Identify the polarisation of the wave given that, Ex = 2 cos wt and Ey = cos wt.

a) Elliptical

b) Circular

c) Parallel

d) Linear

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10. The Snell law is applicable for perpendicular polarisation and the Brewster law is applicable for parallel polarisation. State True/False.

a) True

b) False

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11. When the polarisation of the receiving antenna is unknown, to ensure that it receives atleast half the power, the transmitted wave should be

a) Linearly polarised

b) Elliptically polarised

c) Circularly polarised

d) Normally polarised

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12. Identify the polarisation of the wave given that, Ex = 2 sin wt and Ey = 3 sin wt.

a) Linear

b) Elliptical

c) Circular

d) Parallel