Final answer:
The question asks for the amplitude of the reflected electric field when an electromagnetic wave is incident upon a medium with a given relative permittivity. This requires the use of Fresnel equations to find the reflection coefficient and then use it to determine the amplitude of the reflected wave based on the incident electric field amplitude.
Step-by-step explanation:
The question is related to the reflection of an electromagnetic wave at the boundary between air and another medium with a given relative permittivity (εr=25). We need to determine the amplitude of the reflected electric field (Er) when a plane wave with an electric field amplitude of 9.3 V/m is incident normally upon the surface of this medium.
To solve this, we use the Fresnel equations for reflection, which give us the reflection coefficient at the boundary between two different media. The reflection coefficient (R) for normal incidence is given by:
R = ⅛frac{Z2 - Z1}{Z2 + Z1}
where Z1 and Z2 are the impedances of air and the medium, respectively. For air, Z1 is the impedance of free space (≈ 377 Ω), and for a non-magnetic medium (which typically has μr=1), Z2 can be found using Z2 = Z0/√εr. The electric field amplitude of the reflected wave is then:
Er = R × Ei
where Ei is the amplitude of the incident electric field (9.3 V/m). Plugging in the values and evaluating gives us the amplitude of Er.