Wavicles
It has previously been shown to follow directly from Maxwell’s equations that for an
electromagnetic wave of constant average intensity, the photonic pressure
P
in empty
space is given by
P =
P
/
A
c
, where
P
is the power in the wave,
A
is the area, and
c
is the
speed of light. Pressure, however, is force over area, so
A
can be cancelled in each
denominator to give
F =
P
/c
. Finally, constant force is momentum
p
per unit time just as
constant power is energy
U
per unit time, so after another pair of cancellations, it is found
that an electromagnetic wave can be considered to have a momentum
p = U/c
. Since it
has already been established that the energy in a single photon is
U = hf
, this would seem
to indicate that the massless “
wavicle
” called a photon has a momentum
p = h/
λ
.
Of course, reality is not required to obey results derived mathematically, but in 1922, a
experimental physicist named Compton discovered an effect supporting this idea. He
This is the end of the preview. Sign up
to
access the rest of the document.
This note was uploaded on 04/05/2012 for the course PHYS 131 taught by Professor Tibbets during the Spring '11 term at Cuyamaca College.
 Spring '11
 Tibbets
 Power, Photon

Click to edit the document details