This preview shows pages 1–2. Sign up to view the full content.
ASTRONOMY 822
Electromagnetic Radiation
Problem Set 2
due Wednesday, October 12
at class time
1) Consider a plane electromagnetic wave of the form
~
E
= ˆ
e
y
E
0
cos(
kx

ωt
)
and
~
B
= ˆ
e
z
E
0
cos(
kx

ωt
)
.
The wavelength of the light is measured to be
λ
= 700 nm and its time
averaged energy density is
h
u
i
= 20 erg cm

3
.
a) An electron is placed at the origin, initially at rest (
~x
= 0 and
~v
= 0
at
t
= 0).
Let’s start by assuming that the motions of the electron are
highly nonrelativistic, and that the magnetic forces can be ignored. What
is the force exerted on the electron, in this case?
What is the maximum
displacement of the electron from the origin? What is the maximum velocity
of the electron? Was our assumption of nonrelativistic motions justiFed?
b) The most powerful “petawatt” lasers can produce energy densities as
large as
h
u
i ≈
3
×
10
17
erg cm

3
. Assuming this energy density is provided
by a single plane wave of wavelength
λ
= 1000 nm, what would be the
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview. Sign up
to
access the rest of the document.
 Fall '05
 RYDEN
 Astronomy

Click to edit the document details