A 300 MHz electromagnetic wave in air (medium 1) is normally incident on the planar boundary of a lossless dielectric medium with ϵr = 9 (medium 2). What is the wavelength of the incident wave and the wave in medium 2? What are the intrinsic impedances of media 1 and 2? What are the reflection coefficient and the transmission coefficient at the boundary? If the amplitude of the incident electric field is 10 V/m, what are the maximum amplitudes of the total fields in media 1 and 2? A standing wave pattern appears in medium 1. What are the locations of the first minimum and maximum?

Respuesta :

Answer:

Wavelength of the incident wave in air = 1 m

Wavelength of the incident wave in medium 2 = 0.33 m

Intrinsic impedance of media 1 = 377 ohms

Intrinsic impedance of media 2 = 125.68 ohms

Check the explanation section for a better understanding

Explanation:

a) Wavelength of the incident wave in air

The frequency of the electromagnetic wave in air, f = 300 MHz = 3 * 10⁸ Hz

Speed of light in air, c =  3 * 10⁸ Hz

Wavelength of the incident wave in air:

[tex]\lambda_{air} = \frac{c}{f} \\\lambda_{air} = \frac{3 * 10^{8} }{3 * 10^{8}} \\\lambda_{air} = 1 m[/tex]

Wavelength of the incident wave in medium 2

The refractive index of air in the lossless dielectric medium:

[tex]n = \sqrt{\epsilon_{r} } \\n = \sqrt{9 }\\n =3[/tex]

[tex]\lambda_{2} = \frac{c}{nf}\\\lambda_{2} = \frac{3 * 10^{6} }{3 * 3 * 10^{6}}\\\lambda_{2} = 1/3\\\lambda_{2} = 0.33 m[/tex]

b) Intrinsic impedances of media 1 and media 2

The intrinsic impedance of media 1 is given as:

[tex]n_1 = \sqrt{\frac{\mu_0}{\epsilon_{0} } }[/tex]

Permeability of free space, [tex]\mu_{0} = 4 \pi * 10^{-7} H/m[/tex]

Permittivity for air, [tex]\epsilon_{0} = 8.84 * 10^{-12} F/m[/tex]

[tex]n_1 = \sqrt{\frac{4\pi * 10^{-7} }{8.84 * 10^{-12} } }[/tex]

[tex]n_1 = 377 \Omega[/tex]

The intrinsic impedance of media 2 is given as:

[tex]n_2 = \sqrt{\frac{\mu_r \mu_0}{\epsilon_r \epsilon_{0} } }[/tex]

Permeability of free space, [tex]\mu_{0} = 4 \pi * 10^{-7} H/m[/tex]

Permittivity for air, [tex]\epsilon_{0} = 8.84 * 10^{-12} F/m[/tex]

ϵr = 9

[tex]n_2 = \sqrt{\frac{4\pi * 10^{-7} *1 }{8.84 * 10^{-12} *9 } }[/tex]

[tex]n_2 = 125.68 \Omega[/tex]

c) The reflection coefficient,r  and the transmission coefficient,t at the boundary.

Reflection coefficient, [tex]r = \frac{n - n_{0} }{n + n_{0} }[/tex]

You didn't put the refractive index at the boundary in the question, you can substitute it into the formula above to find it.

[tex]r = \frac{3 - n_{0} }{3 + n_{0} }[/tex]

Transmission coefficient at the boundary, t = r -1

d) The amplitude of the incident electric field is [tex]E_{0} = 10 V/m[/tex]

Maximum amplitudes in the total field is given by:

[tex]E = tE_{0}[/tex] and [tex]E = r E_{0}[/tex]

E = 10r, E = 10t