# Electronics and Communication Engineering - Electromagnetic Field Theory

21.
After reflection from a plane conducting surface, the apparent velocity of electromagnetic wave becomes greater than the velocity of light in free space is called
conventional velocity
phase velocity
propagation velocity
group velocity
Explanation:
No answer description is available. Let's discuss.

22.
In a turnstile antenna the crossed dipoles are excited with voltages
in phase with each other
90° out of phase with each other
120° out of phase with each other
180° out of phase with each other
Explanation:
No answer description is available. Let's discuss.

23.
Directivity of antenna is defined as
maximum directive gain
average directive gain
0
Explanation:
No answer description is available. Let's discuss.

24.
Consider the following; for a loss-less transmission line we can write,
1. Zin = - jz0 for a shorted line with l = λ/8
2. Zin = ± j ∞ for a shorted line with l = λ/4
3. Zin= jz0 for an open line with l = λ/2
4. Zin = 0 for a matched line of any length
Select the correct answer using the codes given below codes.
1, 2
2, 3
1, 3
2, 4
Explanation:
No answer description is available. Let's discuss.

25.
Strip lines are used at
microwave frequency
low frequency
High frequency
at any frequency