### Electronics and Communication Engineering - Electromagnetic Field Theory MCQs Part 10

1.For an incident wave which is normal on the perfect dielectric the reflection factor is given by (where ε1 and ε2 are the permittivities of 1st and 2nd medium respectively)

A.
B.
C.
D.

2.For EM wave propagation in free space, the free space is defined as

A. σ = 0, ε = 1, μ ≠ 1, = 0
B. σ = 0, ε = 1, μ = 1, = 0, = 0
C. σ ≠ 0, ε > 1, μ < 1, ≠ 0, = 0
D. σ = 0, ε = 1, μ = 1, ≠ 0, ≠ 0

3.For TE or TM modes of propagation in bounded media, the phase velocity is

A. independent of frequency
B. is a linear function of frequency
C. is a non-linear function of frequency
D. can be frequency dependent or frequency independent on the source

4.Frequencies in the UHF range propagate by means of

A. space wave
B. surface waves
C. sky waves
D. ground waves

5.Intrinsic or characteristic impedance of free space has a value of

A. 120 ohm
B. 73 ohm
C. 73 ε ohm
D. 120 ε ohm

6.Radiation resistance of half-wave dipole (λ/2) antenna is in free space

A. 73 Ω
B. 120 p
C. 36.5 Ω
D. 70 Ω

7.The effect of the inductance of a coil on a constant direct current is that

A. it does not effect the constant direct current
B. it decreases the current
C. it strengthens the current
D. it causes a higher voltage drop

8.If H = 0.1 sin (108p t + βλ) A/m for a plane wave propagating in free space, then the time average Poynting vector is

A. (0.6psin2 βy) w/m2
B. - 0.6p w/m2
C. 1.2p w/m2
D. - 1.2p w/m2

9.The ratio of tangential component of electric field at the surface of a conductor and the linear current density resulting from this field is __________ impedance

A. characteristic
B. critical
C. surface
D. polarizing

10.The gain of collinear arrays is maximum when the spacing between the elements is

A. 0.1 λ to 0.3 λ
B. 0.3 λ to 0.9 λ
C. 0.5 λ to 0.7 λ
D. 0.7 λ to 0.9 λ