<span>In organic chemistry, covalent bonding is most often associated with carbon compounds, which are known as organic chemicals. Hydrogen is also involved most of the time, as well as oxygen. Other elements can also be involved, but less frequently.</span>
That depends on the wave, if you're talking about sound, it makes matter move in a similar wavelength as them, a mountainous shape. Light however would make whatever matter it hits start to move in the same direction as the light's angle of approach.
So this can explain the density of a person very clearly.
