It simply is a second derivative of electric field of charge (magnetic field is first). If charge moves with constant velocity - we only have first derivative (B), if with variable velocity (=acceleration) - then we have both B and new component of E ("on top" of E of non-moving) charge.

So, no need to have propagating charge. Thus, no effect from constant E or B on a photon.

The reason photons of some energy interact with matter more strongly than other is simple: if a photon's energy (=energy of e/m field) is NOT enough to change state of matter (=of electron or proton), it can not - symmetry of time (=energy conservation) does not let it to. So, low energy photons (radio waves) simply do not have enough energy to change state of bonded electron because electron's energy is quantizied in atom. In contrast,FREE electron does not have quantizied states, thus can easily change its energy. Thus metals (=free electrons) affect ANY low energy photons. Shielding and reflection ("silverish" appearance) is a consequense.

Too high energy photon (gamma rays) have so much energy left after it shared part of it with bonded electron it still have plenty left (= it moves deeper and deeper in matter until loses all its energy).

The reason a photon moves with c is it's lack of rest mass (which would take time to accelerate).

About internet search - I very RARELY do that. 3 reasons: 1) I am lazy (I admit that). 2) In 99% cases I know the answer right out of my head, or can find the answer with a pen and a paper (and sometimes a calculator) because this is my profession. Therefore, no need to go further. 3) Web is very (and very!) littered with poor quality information, wrong opinions, incorrect representation of facts, etc. (I also feel this from your responds). My advice: be selective when you trying to find something there - it is same sea of low-educated opinions out there as in any other non peer-reviewed media (if not more). Freedom of speach, after all.

• Ball? - luis_hamburgh - November 4, 2001 - 23:35 UTC
  • Forgot to ask... - luis_hamburgh - November 4, 2001 - 23:36 UTC
    • Next possible level down? - alexander - November 5, 2001 - 00:36 UTC
      • Two squared questions - luis_hamburgh - November 6, 2001 - 00:00 UTC
        • Some string models predict graviton to be 5 dimensional. - alexander - November 6, 2001 - 02:07 UTC
• Alex: Do you think Ditchburn's book is good? - dolphin - November 7, 2001 - 07:07 UTC