Electronics and Communication Engineering - Electromagnetic Field Theory - Discussion

Discussion Forum : Electromagnetic Field Theory - Section 1 (Q.No. 10)
10.
A rectangular metal waveguide filled with a dielectric of relative permittivity εr = 4, has the inside dimensions 3 x 1.2 cm, the cut off frequency for the dominant mode is
2.5 GHz
5 GHz
10 GHz
12.5 GHz
Answer: Option
Explanation:

for dominant mode.

Discussion:
15 comments Page 1 of 2.

Kamlesh said:   1 decade ago
Option A is correct.

Phase velocity is c/2 hence f = c/4a.

Vinay said:   1 decade ago
Yes option A is correct.

C' = C/2.

Allaa said:   1 decade ago
c = c0/sqrt(εr).
f = c/2a.

Ravi said:   9 years ago
Cut off frequency = c/(2a * sqrt (Er * Ur).

Anjli said:   9 years ago
As f = C'/2a.

And C' = C/2 (because Er = 4).

So f = c/4a.

Pk rai said:   9 years ago
A is correct.

Sunil Chavan said:   8 years ago
A is the answer.

Ronston said:   8 years ago
What does 'a' stand for? dimension?

Azar said:   8 years ago
fc = C/2a.

fc = Cut-off Frequency.
C = Speed of Light = 3 * 10^8,
a = Width = 3 cm.

fc = 3 * 10^8 / 2 *3 = 0.5 * 10^8 ==> 5 GHz.

Vijay said:   8 years ago
Fc should be divided by 2.


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