Electronics and Communication Engineering - Electromagnetic Field Theory

21. 

Velocity of the wave when it passes from air into sphere

A. decreases
B. increases
C. same
D. no change

Answer: Option B

Explanation:

No answer description available for this question. Let us discuss.

22. 

The ratio of the directivity of an end fire antenna to that of a broadside antenna is

A. 2
B. 3
C. 4
D. 5

Answer: Option A

Explanation:

In Broadside, D = 2n

In End fire D = 4n.


23. 

If the electric field intensity associated with a uniform plane electromagnetic wave travelling in a perfect dielectric medium is given by
E(z, t) = 10 cos (2p x 107t - 0.1 pz) volt/metre, then the velocity of the travelling wave is

A. 3.0 x 108 m/sec
B. 2 x 108 m/sec
C. 6.28 x 107 m/sec
D. 2 x 107 m/sec

Answer: Option B

Explanation:

E(z, t) = 10 cos (2p x 107t - 0.1 pz)

f = 107 Hz, β = 0.1p


24. 

The absorption of radio waves by atmosphere depends on

A. their frequency
B. their distance from the transmitter
C. the polarization of atmosphere
D. the polarization of the waves

Answer: Option A

Explanation:

No answer description available for this question. Let us discuss.

25. 

For transmission-line matching over range of frequencies, it is best to use a

A. single stub of adjustable position
B. double stub
C. broadband directional coupler
D. balun

Answer: Option B

Explanation:

No answer description available for this question. Let us discuss.