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A plane wave having the electric field component $\vec{E}_{\mathrm{t}}=24 \cos \left(3 \times 10^{3} t-\beta y \right) \hat{a}_{z} \mathrm{~V} / \mathrm{m}$ and traveling in free space is incident normally on a lossless medium with $\mu=\mu_{0}$ and $\varepsilon=9 \varepsilon_{0}$ which occupies the region $y \geq 0$. The reflected magnetic field component is given by

1. $\frac{1}{10 \pi} \cos \left(3 \times 10^{\mathrm{k}} t+y\right) \hat{a}_{1}, \mathrm{~A} / \mathrm{m}$
2. $\frac{1}{20 \pi} \cos \left(3 \times 10^{k} t+y\right) \hat{a}_{x} \mathrm{~A} / \mathrm{m}$
3. $-\frac{1}{20 \pi} \cos \left(3 \times 10^{s} t+y\right) \hat{a}_{1} \mathrm{~A} / \mathrm{m}$
4. $-\frac{1}{10 \pi} \cos \left(3 \times 10^{8} t+y\right) \hat{a}_{1} \mathrm{~A} / \mathrm{m}$