http://en.wikipedia.org/wiki/Longitudinal_wave[Longitudinal wave]

http://en.wikipedia.org/wiki/Wavelength[More info on Wavelength]


-The Difference is the Wavelength
The bar above the wave represents one wavelength. This is the distance between any two successive crests (high points) of the wave and is identical to the distance between any two troughs (low points) of the wave. All electromagnetic waves are similar; only their wavelength is different.
-Heat transfer
Is the transition of thermal energy from a hotter mass to a cooler mass. When an object is at a different temperature than its surroundings or another object, transfer of thermal energy, also known as heat flow, or heat exchange, occurs in such a way that the body and the surroundings reach thermal equilibrium; this means that they are at the same temperature. Heat transfer always occurs from a higher-temperature object to a cooler-temperature one

-Heat Convection
Convection is heat transfer by mass motion of a fluid such as air or water when the heated fluid is caused to move away from the source of heat, carrying energy with it. Convection above a hot surface occurs because hot air expands, becomes less dense, and rises (see Ideal Gas Law). Hot water is likewise less dense than cold water and rises, causing convection currents which transport energy.