when the two waves interfere with eachother to make a dark spot the periodic difference of the two waves is π . the wave length for 2π is 600nm
. ie. for π difference it is 300nm
Longitudinal waves have energy that vibrates parallel to the medium - a compression is the region of greatest density and the rarefaction the region of highest density .The rarefaction (much like the maximum amplitude in a transverse wave) has a region of lowest density, typically situated in the exact center of the region.
They cause an increase in temp of earths atmosphere or warming by absorbing solar energy. hope this helps
