Question 131. 3. The longest wavelength that can be absorbed by silicon, which has the bandgap of 1.12 eV, is 1.1 pm. If the longest wavelength that can be absorbed by another material is 0.87 pm, then the bandgap of this material is

Question 132. 0. In a rectangular waveguide there is one half-wave variation of a electric field across the narrow dimension and two half-wave variations of electric field across the wider dimension. What is the dominant mode?

Question 133. 2. The phase velocity of an electromagnetic wave propagating in a hollow metallic rectangular waveguide in the TE10 mode is

Question 134. 5. Characteristic impedance of a transmission line is 500. Input impedance of the open-circuited line is Zoc = 100 + j150 Q. When the transmission line is short-circuited, then value of the input impedance will be

Question 135. 4.  A lossless transmission line is terminated in a load which reflects a part of the incident power. The measured VSWR is 2. The percentage of the power that is reflected back is

Question 136. 7. A 30-Volts battery with zero source resistance is connected to a coaxial line of characteristic impedance of 50 Ohms at t = 0 second and terminated in an unknown resistive load. The line length is such that it takes 400 gs for an electromagnetic wave to travel from source end to load end and vice-versa. At t = 400 gs, the voltage at the load end is found to be 40 Volts The steady-state current through the load resistance is

Question 137. 9. The field in a rectangular waveguide of inner dimensions a x b is given by, where Ho is a constant, and a and b are the dimensions along the x-axis and the y-axis respectively. The mode of propagation in the waveguide is

Question 138. 6. A 30-Volts battery with zero source resistance is connected to a coaxial line of characteristic impedance of 50 Ohms at t = 0 second and terminated in an unknown resistive load. The line length is such that it takes 400 gs for an electromagnetic wave to travel from source end to load end and vice-versa. At t = 400 gs, the voltage at the load end is found to be 40 Volts.I The load resistance is

Question 139. 8. An air-filled rectangular waveguide has inner dimensions of 3 cm x 2 cm. The wave impedance of the TE20 mode of propagation in the waveguide at frequency of 30 GHz is (free space impedance go =377 CZ)

Question 140. 1.  A lossless transmission line is terminated in a load which reflects a part of the incident power. The measured VSWR is 2. The percentage of the power that is reflected back is