Wavelength & frequency
The one equation behind every antenna, radio telescope and radar: wavelength equals speed divided by frequency. Run it forward, run it backward, and see what happens when the wave travels through ice or rock instead of empty space.
Speed of light
Most classroom problems (and the Cosmic Sanctuary packets) use the rounded value. Switch to the exact value to see how small the difference is: about 0.07%.
One wave
Inside a material a radio wave slows to v = c/√εr, so the same frequency has a shorter wavelength. Permittivity values for real materials vary with temperature, moisture and frequency; the presets are typical round numbers.
A frequency band
An instrument that must work across a band of frequencies has to handle the longest wavelength (lowest frequency) and the shortest (highest frequency) at the same time.