解釋如下
Question: DOES THE ELECTRON TRAVEL AT THE SPEED OF LIGHT?
------------------------------------------------
Answer: No. If you calculate the instantaneous speed of electron
using the theoretical models it comes out to be the velocity
of light. However we cannot measure instantaneous speeds but only
speed averaged over some time scale by measuring position at two
instants of time. When we do this the speed is always less than
the velocity of light. Theoretical models also predict average
velocity less than speed of light.
The above discussion only applies to speed of light
in vacuum. Electrons can and do travel at
speeds faster than
speed of light in some media.
Jasjeet
SOURCE FROM http://www.newton.dep.anl.gov/askasci/phy99/phy99372.htm作者: stephenyeong 時間: 2005-9-24 01:58:11
解釋如下
Question: DOES THE ELECTRON TRAVEL AT THE SPEED OF LIGHT?
------------------------------------------------
Answer: No. If you calculate the instantaneous speed of electron
using the theoretical models it comes out to be the velocity
of light. However we cannot measure instantaneous speeds but only
speed averaged over some time scale by measuring position at two
instants of time. When we do this the speed is always less than
the velocity of light. Theoretical models also predict average
velocity less than speed of light.
The above discussion only applies to speed of light
in vacuum. Electrons can and do travel at
speeds faster than
speed of light in some media.
Jasjeet
SOURCE FROM http://www.newton.dep.anl.gov/askasci/phy99/phy99372.htm[/quote]
Speed of electron ??
drift velocity of electron作者: Billy 時間: 2005-9-24 09:00:44
[quote:566d81728d="stephenyeong"][quote:566d81728d="wychan"]Electrons can and do travel at
speeds faster than
speed of light in some media.
Jasjeet
[/quote]
electron travel speed in wire is very slow although free electron can travel at speed of 50% C. Drift velocity of electron is slower then 1m/s.
speed of light / em wave is the maximum speed in specified medium / environment.
Speed of light in vaccum is around 300000000 m/s[/quote]
this may be caused by the mass of electron (in term of wave density) is heavier then photon.作者: wychan 時間: 2005-9-24 12:49:36
[quote:614763bba5="stephenyeong"][quote:614763bba5="wychan"]Electrons can and do travel at
speeds faster than
speed of light in some media.
Jasjeet
[/quote]
electron travel speed in wire is very slow although free electron can travel at speed of 50% C. Drift velocity of electron is slower then 1m/s.
speed of light / em wave is the maximum speed in specified medium / environment.
Speed of light in vaccum is around 300000000 m/s[/quote]
this may be caused by the mass of electron (in term of wave density) is heavier then photon.作者: hales 時間: 2005-9-24 13:03:14
[quote:9f6e40f8e4="wychan"][quote:9f6e40f8e4="stephenyeong"][quote:9f6e40f8e4="wychan"]Electrons can and do travel at
speeds faster than
speed of light in some media.
Jasjeet
[/quote]
electron travel speed in wire is very slow although free electron can travel at speed of 50% C. Drift velocity of electron is slower then 1m/s.
speed of light / em wave is the maximum speed in specified medium / environment.
Speed of light in vaccum is around 300000000 m/s[/quote]
this may be caused by the mass of electron (in term of wave density) is heavier then photon.[/quote]
it always be Ture Photon is "Mass-less"......
但係有o的野好似....搞錯左喎.........
以我讀physical chem所學到既....
one more hints
點解光會折射? 折射率又是什麼?作者: unicorn 時間: 2005-9-24 20:42:22
所以我問signal的速度 不是electron 的速度.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
oops
your question is REALLY a question to elect engineer
not to physics guys
for a signal in 電線 it depends very much on those cap/inductance operating frequency and also the VOLATAGE
of how a CAT 5 cable can function
即係我地日日overclock PC既topics
however
for a optics fibre
it only depends on the signal wavelength and the modulator demodulator and media etc
that is why 電線 technology bandwidth advancement慢
that is why opto technology bandwidth advancement快
同時 v =c/n.........
咁光纖既..n又係乜呢?作者: stephenyeong 時間: 2005-9-24 22:42:45
[quote:c5000ffce6="hales"]你呢個0.7C係因為......
因為光線在光纖內要透過"全反射"來把光學signal 傳送
所以 光線本身internal既optical pathway distance係長過 光纖既phyical lenght?[/quote]
不是... 光之所以會折射 因為光的速度在不同介質會唔同.
reflective index = c/n n means speed of light in medium
而glass的reflective index 大約1.5 光在glass的速度大約66%...
plastic 的reflective index 應該有1.6.. (剛在綱search過)
光在fiber的pathway應該不會太長 因為fiber的diameter只不過900μm (0.1mm)作者: Billy 時間: 2005-9-24 23:53:04