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A medium of relative permittivity $\varepsilon_{r 2}=2$ forms an interface with free-space. A point source of electronagnetic energy is located in the medium at a depth of $1$ meter from the interface. Due to the total internal reflection, the transmitted beam has a circular cross-section over the interface. The area of the beam cross-section at the interface is given by

1. $2 \pi \; m^{2}$
2. $\pi^{2} \mathrm{~m}^{2}$
3. $\frac{\pi}{2} \mathrm{~m}^{2}$
4. $\pi \; \mathrm{m}^{2}$