Which wave characteristic is the same for all electromagnetic waves traveling through a vacuum?

If a substance is in the gas phase, which of qualities of the gas will stay constant? a: volume b: mass c: shape d: position of particles

Which is special about a dc circuit ? a. it has both series and parallel components b. it has only series or only parallel components c. charge moves in a single direction d. charge moves back and forth quickly

Ihave a density of 1.61g/cm^3 and a mass of 28g. find the missing value