Electronics and Communication Engineering - Electromagnetic Field Theory

26. 

Consider a loss less antenna with a directive gain of + 6 dB. If 1 mW of power is fed to it the total power radiated by the antenna will be

A. 4 mW
B. 1 mW
C. 7 mW
D. 1/4 mW

Answer: Option A

Explanation:

6 dB = 10 log10

= 100.6 3.98

Pr = 3.98 mW.


27. 

A uniform plane wave is one in which

A. x = 0
B. .
C. and are perpendicular
D. and lie in a plane

Answer: Option D

Explanation:

For uniform plane wave, E and H must be in a plane but perpendicular to each other.


28. 

The electric field of the incident wave is , where ω = 3 x 109p and β = 10 p. The electric field of the transmitted wave Et is given by

A.
B.
C.
D.

Answer: Option C

Explanation:

In, question, it is not mentioned, about medium; dielectric etc.

Ei = Et + Er

Et = Er

Et = Ei.


29. 

A short circuited stub is shunt connected to a transmission line as shown in the figure is, if z0 = 500 ohms, the admittance y seen at the function of the stub and the transmission line is

A. (0.01 - j 0.02) mho
B. (0.02 - j 0.01) mho
C. (0.04 - j 0.02) mho
D. (0.02 + j 0) mho

Answer: Option A

Explanation:


30. 

Which of the following should dominant wave have?

A. Lowest cut off frequency
B. Highest cut off frequency
C. No attenuation
D. No phase shift

Answer: Option A

Explanation:

Lowest cut off frequency or highest wave-length in a waveguide gives dominant modes.