18. Following the previous question, what is the electric field of the transmitted wave?
(A)
(B)
(C)
(D) None of the above.

14. Consider a sheet current source at z =0. The medium on either side of the sheet is perfect dielectric. Assume the dielectric constant is higher in the z ＞0 region. Which of the following statcments is not correct? (A) The power flux is higher in the z＞0 region. (B) The power flux is higher in the z ＜0 region. (C) The power flux is the same in both regions (D) There is no power flux in both regions.

15. Assume the relation holds in a medium, where ε is a constant. What do we not imply for that medium? (A) The medium is linear. (B) The medium is isotropic. (C) The medium is nondispersive. (D) The medium is lossless.

複選題16. Assume two electromagnetic waves (frequency fA and fB) enters a nonlinear material whose polarization field includes a term that is proportional to the square of the clectric field. Which of the following frequencies could one possibly observe at the output of the nonlincar material? (A) fA+ fB(B) 2fA (C) 2fB (D) All of the above.

17. Consider a situation that region 1 (z ＜0) is free space and region 2 (z ＜0) is an anisotropic lossless nonmagnetic material described by the following reiationship.  For a uniforn piane wave with the electric field incident on the interface z =0 form region I. What is the electric field of the reflected wave?(A) (B)(C) (D) None of the above.

19. A randomly polarized electromagnetic wave in free space is incident on a lossless medium with a diclectric constant of 3. At what incident angle does the reflected wave become linearly polarized? (A) 0 degree (B) 30 degrees (C) 60 degrees(D) None

20. Assume the electron density is 106 cm-3 in a certain layer of ionsphere. Which of the following frequency of electromagnetic waves that could pass through that layer? (A) 12 MHz (B) 8 MHz (C) 4 MHz (D) 1 MHz

21.If V/m. Find (z，t). (A)mA/m (B)mA/m (C)mA/m (D)m/Am

22. In an air-filled parallel-plate waveguide with dimension a = 4 cm, according to the expression of electric field distribution, E= E0(sin25πx+3sin50πx)sin(8x109πt) What is the value of phase constantβ2 of propagation wave? (A) 7.5 (B) 23.5 (C) 29.2 (D) 74 radm

23. Consider a parallel-plate waveguide (plates at y=0and y=b planes), with wave propagating in the +z direction. For the lowest-order TM mode, if the instantaneous field expression for the z-component of the clectric field at (x, y, z) = (x, b/4. 0) is Ez(t) = E0cos wt, what is the corresponding expression for Ez(t) at (x, y, z) = (x. b/2, d)? (A)2E0cos(wt-βd)(B)(C)2E0sin(wt-βd)(D) sin(wt-βd)

24. Find the spacing d for a parallel-plate waveguide having a dielectric of ε =4ε0, and u= u0 such that 5 GHz is the cutotr frequency of the dominant mode. (A) 1(B)1.5 (C)2 (D) 2.5 cm