This document provides information about waveguides, including: 1) A rectangular waveguide with dimensions of 5cm by 3cm is operating the TM11 mode, and the cut-off frequency is calculated to be 5.83MHz. 2) Cut-off frequencies and the number of supported modes are calculated for a rectangular waveguide with dimensions of 3.5cm by 2cm operating below 15GHz. 3) Operating parameters like cut-off frequency, waveguide impedance, time delay, and frequency range are calculated for a 7.5cm by 4.5cm rectangular waveguide operating at 3GHz.