|
|
On the previous couple of pages I introduced Planck's revolutionary idea that the energy of EM waves is quantized
into particles called photons.
Let us see some of the properties of photons.
- The energy of a photon related to an electromagnetic wave whose frequency is
 is given by 
- We know light propagates with the speed of light. Therefore the speed of photons is c.
- The rest mass
 of a
photon is 0.
We learned earlier that objects with nonzero rest mass cannot propagate with the speed of light. This comes
from the fact, that if you calculate the dynamical mass for greater than 0 and v=c, you get nonsense, a diverging expression.
It looks as if the dynamical mass became infinite, which means the energy of the particle became infinite. However,
if the rest mass is zero, you get 0/0, which in mathematics means an arbitrary number. By using mathematical tricks
(limits), one can still extract some information from such limits and get a meaningful value for the dynamical
mass.
This last item is very important. It sets the bridge between the particle and wave description of the world,
as we will see on the next page.
|
Photoeffect
(just as in classical
physics, momentum equals mass times speed) which gives us 