Assertion: radio wave's amplitude | /r/CapableOf | vary with time
Facets:
value: cyclically
type: DEGREE
Source sentences:
text: Both are propagated through space in approximately straight lines at a velocity of about 300,000,000 metres (186,000 miles) per second and have amplitudes that vary cyclically with time; that is, they oscillate from zero amplitude to a maximum and back again.