Bent Sticks and Lightning Bolts
Each one of these wave modes can be transformed into any of the others. This is usually done by changing the angle at which a wave travels from a medium of a given density into another medium of another density. This is why a stick placed under water looks like it is bent in two pieces. The light traveling through the air is one mode (longitudinal) and becomes a Shear or Transverse mode once it strikes and travels through the water. The water is much denser than the air and causes the light ray to "bend" as it passes from the air in to the water. The very same thing happens with sound traveling through the air. You can hear this quite plainly during a thunderstorm. The thunder can be heard to rumble from lower to higher pitches. There are heard echoes and multiple occurrences of sound resulting from a single lightning clap. During a thunderstorm there are zones of cold and warmer air in the vicinity of these storms. The colder air is denser than the warmer air and the sound will refract (change mode) as it travels through these zones of differing densities.
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