It is often necessary to change the physical direction of ...

[abern]

It is often necessary to change the physical direction of propagation or the wave's polarization in waveguides. What is the purpose of a twist section?
 
  A. To produce shunting reactance across the guide
  B. To change the plane of polarization of the wave
  C. To change the physical direction of propagation
  D. So low received power does no damage to the powerful transmitter output

Question 2

Why is a waveguide often pressurized with nitrogen?
 
  A. To prevent contamination
  B. To change the plane of polarization of the wave
  C. To attach or weld a metal plate at the end of the waveguide
  D. To prevent reflections

[Jsherida]

Answer to Question 1

B

Answer to Question 2

A