CALCULATION FOR RADAR TYPE LEVEL INSTRUMENT :
Radio waves travel at the velocity of light 2" 2.9979 x 10 rest to 8 meters per second in a perfect vacuum.
A formula relating wave velocity to relative permittivity (the ratio of a substance's permittivity to that of a perfect vacuum, symbolized as εr and sometimes called the dielectric constant of the substance) and the velocity of light in a perfect vacuum (c)
is shown here :
where Er is,