They differ from each other<span> in wavelength. Wavelength is the distance between </span>one wave<span> crest to the next. </span>Waves<span> in the </span>electromagnetic<span> spectrum vary in size from very long radio </span>waves<span> the size of buildings, to very short gamma-rays smaller </span>than<span> the size of the nucleus of an atom.</span>
Direction and Strength can be measured of force
When paper burns, some of the chemical compounds in the
paper combine with oxygen in the air and become different
chemical compounds. That's a chemical change.
When iron rusts, or copper or silver turns green, that's the result
of the metal at the surface combining with the oxygen in the air and
forming a new chemical compound. Those are chemical changes.
When water evaporates, H₂O in the liquid phase gains thermal
energy and changes to H₂O in the gaseous phase. No chemical
compounds are lost, gained, or changed to other compounds.
It's just a physical change.
Density is defines as the ratio of mass to volume.
So you measure the mass and volume of a sample, and
divide the mass by the volume, to find the density.