Electronics and Communication Engineering - Electromagnetic Field Theory

11. 

A wave is propagated in a waveguide at frequency of 9 GHz and separation is 2 cm between walls Calculate group velocity for dominant mode.

A. 1.8 x 108 m/sec
B. 5 x 108 m/sec
C. 3 x 108 m/sec
D. 1.5 x 108 m/sec

Answer: Option A

Explanation:

Vg . Vp = C2

where

.


12. 

For F1 layer the maximum ionic density is 2.3 x 104 electrons per cc. The critical frequency for this layer will be

A. 1.36 MHz
B. 13.6 MHz
C. 136 MHz
D. 1360 MHz

Answer: Option B

Explanation:

fc = 9Nmax .


13. 

Which one of the following does represents the electric field lines for the TE02 mode in the cross section of a hollow rectangular metallic waveguide?

A.
B.
C.
D.

Answer: Option C

Explanation:

TE02 m = 0, n = 2

in x direction no propagation, only in y, and normal to the waveguide, tangential component is continuous.


14. 

The velocity of electromagnetic wave in a good conductor is

A. 3 x 108 m/s
B. more than 3 x 108 m/s
C. very low
D. high

Answer: Option C

Explanation:

, for good conductor εr >> 1.


15. 

Radiation intensity of a dipole depends strongly on frequency. If at a frequency f, the intensity of radiation is 'I'. Then at a frequency of f/2, the intensity will be

A.
B.
C.
D.

Answer: Option A

Explanation:

I ∝ f.