Wave(Longtitudinal wave and transverse wave and EM wave)

Hope you wouldn't mind me answering in English! =] (My chinese typing is really slow and I learnt this in English)


1. http://en.wikipedia.org/wiki/Seismic_wave
地震波 ie. Seismic waves come in two types - P and S waves. P waves are longitudinal, but S waves are transverse.


2. For wave-particle duality of light: Einstein's photoelectric effect.
Einstein suggested that light comes in packets of energy - what u refer to as 粒子 is actually 光子, photons. At the same time, light can exist as a wave, for example, we see it can refract (折射) in water. Also, if you've read about Young's double slit experiment (http://en.wikipedia.org/wiki/Double-slit_experiment) you'll know that light also diffracts and causes interference.


3. First you have to understand what the definitions of longitudinal and transverse waves are:

Longitudinal: waves that have vibrations along or parallel to their direction of travel; that is, waves in which the motion of the medium is in the same direction as the motion of the wave.
http://en.wikipedia.org/wiki/Longitudinal_wave

Transverse - a moving wave, a wave that propagates (travels) in a direction perpendicular to the direction in which the oscillations that produce the wave are moving.
http://en.wikipedia.org/wiki/Transverse_wave

If you take a look at the two wikipedia pages, you'll see two animation to do with the 環形 waves you talked about. Both longitudinal or transverse waves can spread in rings, but if you know what the nature of the wave is (e.g. soundwaves are longitudinal, whereas waves in the sea is transverse.) you can define which type of wave it is. Most waves should be transverse though.

Hope this helps!