煩請physics知識長 幫幫手

1. This is the interaction of electromagnetic waves with atoms. The orbital electrons of an atom is perturbated by the electric field of the wave, which causes them to oscillate and thus absorb the incident waves. The absorbed energy is re-emitted as scattered waves. This situation is similar to a forced oscillation in which the driving frequency is much greater than the natural frequency of the atoms. The resulted in the difference in scattered wave intensity with different frequency waves.

Detailed mathematical explanation of the process can be found in the following web-page:

http://farside.ph.utexas.edu/teaching/em/lectures/node97.html

2. It is not Lenz' Law. It is Faraday's Law and Ampere's Law. The two laws describe that a changing electric field induces a magnetic field, and a changing magnetic field induced an electric field. Since fields themselves can exit in vacuum (be aware that vacuum possesses a non-zero permitivity and permeability), electromagentic waves propagate by mutual induction of the eelctric and magnetic fields.

3.This is only a common practice. Generally, the electric field component of the electromagentic wave has greater interaction on electrons and atomic dipoles in substances.


4. Again, detailed explanation needs to rely on mathematical manipulation using Maxwell's Electromagentic Equations. A simple explanation is that certain crystal structure allows electric field vibration in a certain direction to pass through, but absorb electric field vibration in other directions.