If r is relative permeability, r is relative permittivity, c is velocity of light fc is cutoff frequency, phase velocity vp (i.e., speed with which a particular phase of the wave travels down a rectangular waveguide at frequency f) is given by

• A. <img src="/_files/images/electronics-and-communication-engineering/microwave-communication/12-95-1.png">
• B. <img src="/_files/images/electronics-and-communication-engineering/microwave-communication/12-95-2.png">
• C. <img src="/_files/images/electronics-and-communication-engineering/microwave-communication/12-95-3.png">
• D. <img src="/_files/images/electronics-and-communication-engineering/microwave-communication/12-95-4.png">