The Depth of penetration of EM wave in medium having conductivity ? at a frequen

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Question
The Depth of penetration of EM wave in medium having conductivity ? at a frequency of 1 MHz is 25 cm. The depth of penetration at a frequency of 4 MHz will be
Options
A. 6.25 cm
B. 12.50 cm
C. 50 cm
D. 100 cm

Correct Answer

12.50 cm

Explanation

Skin depth

The Depth of penetration of EM wave in medium having conductivity ? at a frequency of 1 MHz is 25 cm

The Depth of penetration of EM wave in medium having conductivity ? at a frequency of 1 MHz is 25 cm

⟹ ?₂ = ?₁/2 .

Electromagnetic Field Theory problems

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1. For a 400 kHz transmission line having L = 0.5 mH/km, C = 0.08 mF and negligible R and G, the value of propagation constant P will be
Options
A. 15.9 radians/km
B. 31.8 radians/km
C. 63.6 radians/km
D. 105.4 radians/km

2. A parallel polarized wave is incident from air into paraffin having relative permittivity 3, the value of its Brewster angle is
Options
A. 0�
B. 30�
C. 45�
D. 60�

3. 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?
Options
A.
B.
C.
D.

4. The velocity of electromagnetic wave in a good conductor is
Options
A. 3 x 10⁸ m/s
B. more than 3 x 10⁸ m/s
C. very low
D. high

5. The displacement flux density at a point on the surface of a perfect conductor is = 2(a_x - 3 a_z)c/m² pointing away from the surface. The charge density at that point c/m² will be
Options
A. 2
B. - 2
C. 4
D. - 4

6. 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
Options
A.
B.
C.
D.

7. The divergence of the electric field intensity at any point equals
Options
A. 1/4 p?₀ times the volume charge density
B. l/?₀ times the volume charge density at that point
C. ?₀ times the volume charge density at that point
D. the volume charge density at that point

8. A broadside array operating at 100 cm wavelength consist of 4 half-wave dipoles spaced 50 cm apart. Each element carries radio frequency current in the same phase and of magnitude 0.5 A. The radiated power will be
Options
A. 196 W
B. 73 W
C. 36.5 W
D. 18.25 W

9. A rectangular metal waveguide filled with a dielectric of relative permittivity ?_r = 4, has the inside dimensions 3 x 1.2 cm, the cut off frequency for the dominant mode is
Options
A. 2.5 GHz
B. 5 GHz
C. 10 GHz
D. 12.5 GHz

10. Two identical antennas are placed in the ? = p/2 plane as shown in the figure. The elements have equal amplitude excitation with 180� polarity difference, operating of the far-zone resultant electric field strength normalized with that of a single element, both computed for ? = 0, is
Options
A.
B.
C.
D.

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