This preview shows pages 1–3. Sign up to view the full content.
4/21/08 2:21 AM
MasteringPhysics
Page 1 of 10
http://session.masteringphysics.com/myct
Assignment Display Mode:
View Printable Answers
Physics 202
Assignment 11
Due at 11:00pm on Wednesday, April 16, 2008
View Grading Details
Electric and Magnetic Field Vectors Conceptual Question
Description:
Short conceptual questions about the direction the electromagnetic wave, electric field, and magnetic field
vectors point.
Part A
The electric and magnetic field vectors at a specific point in space and time are illustrated. Based on this information, in
what direction does the electromagnetic wave propagate?
Hint A.1
Righthand rule for electromagnetic wave velocity
In an electromagnetic wave, the electric and magnetic field vectors are perpendicular to each other. The wave propagates
in a direction perpendicular to both of the field vectors. Since the two field vectors define a twodimensional plane, there
are two distinct directions that are perpendicular to the plane. The righthand rule specifies in which of these two
directions the wave travels.
To employ the right hand rule, do the following:
1. Point the fingers of your right hand in the direction of the electric field vector.
2. Rotate your hand until you can curl your fingers in the direction of the magnetic field vector.
The direction of your thumb is then the direction of the velocity of the electromagnetic wave.
If the electric and magnetic field vectors at a specific point in space and time are as shown below, applying the right
hand rule should result in your thumb pointing downward, in the –
y
direction. Therefore, the velocity of the
electromagnetic wave is in the –
y
direction.
ANSWER:
+
x
–
x
+
y
–
y
+
z
–
z
at a +45
angle in the
xy
plane
Part B
The electric and magnetic field vectors at a specific point in space and time are illustrated. (
and
are in the
xy
plane.
Both vectors make 45
angles with the
y
axis.) Based on
this information, in what direction does the electromagnetic
wave propagate?
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document4/21/08 2:21 AM
MasteringPhysics
Page 2 of 10
http://session.masteringphysics.com/myct
ANSWER:
+
x
–
x
+
y
–
y
+
z
–
z
at a –45
angle in the
xy
plane
Part C
The magnetic field vector and the direction of propagation of an electromagnetic wave are illustrated. Based on this
information, in what direction does the electric field vector
point?
Hint C.1
Working backward with the righthand rule
Since the velocity of the wave is given, the orientation of your right thumb is known. Placing your right thumb along the
+
x
axis should inform you that the electric field vector must be in the
yz
plane. Since the electric field must also be
perpendicular to the magnetic field, and be "curlable" into the magnetic field, only one option remains for the orientation
of the electric field vector.
ANSWER:
This is the end of the preview. Sign up
to
access the rest of the document.
 Fall '08
 All
 Physics

Click to edit the document details