### Electronics and Communication Engineering - Electromagnetic Field Theory MCQs Part 7

1.When the phase velocity of an EM wave depends on frequency in any medium, the phenomenon is called

A. scattering
B. polarization
C. absorption
D. dispersion

2.A hertzian dipole has a radiation pattern with

A. a null in the direction of the dipole
B. a null in the plane perpendicular to the dipole
C. a peak in the direction of the dipole
D. none of the above

3.Circular polarized waves result when

A. magnitudes are the same
B. phases are the same
C. magnitudes are same and phase difference is 90°
D. magnitudes are same and phase difference is zero

4.Permeance is analogue to

A. reluctance
B. conductance
C. capacitance
D. resistance

5.Skip distance (D) is

A. (D ∝ f)
B.
C. D = f
D. D < f

6.A very reliable service has to be established between two points on earth separated by 1000 km. The band that will be used as

A. MF
B. VHF
C. VLF
D. HF

7.A rectangular waveguide (2.29 x 1.02) cm operates at a freq. of 11 GHz in TE10 mode. If the maximum potential gradient of the signal is 5 kV/cm, then the maximum power handling capacity of the waveguide will be

A. 31.11 mW
B. 31.11 W
C. 31.11 kW
D. 31.11 MW

8.A parabolic antenna produces a radiation pattern which is

A. circularly polarized
B. highly directional
C. omnidirectional
D. linearly polarized

9.Considerable ionization occurs between the range

A. 50 km to 400 km
B. 100 to 400 km
C. 50 km to 250 km
D. 10 to 50 km

10.Gain of isotropic antenna is

A. 10 dB
B. 0 dB
C. ∞
D. 1 dB