Is "The Wave" at the stadium a transverse wave or a longitudinal wave?
1. Transverse
2. Longitudinal
3. Neither
Note:
* Correct Answer: A
A wave on a stretched drum head is an example of a:
1. transverse wave
2. longitudinal wave
3. it's not a wave at all
Note:
* Correct Answer: A
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* Quiz next Friday (Maxwell Ampere + Poynting Vector)
* Determine the electric and magnetic field in a situation where there is a displacement current
* Discuss the direction of the Poynting vector and how it relates to conservation of energy
The electric field for a plane wave is given by:
$$\mathbf{E}(\mathbf{r},t) = \mathbf{E}_0e^{i(\mathbf{k}\cdot\mathbf{r} - \omega t)}$$
The vector $\mathbf{k}$ tells you:
1. The direction of the electric field vector.
2. The speed of the traveling wave.
3. The direction the plane wave moves.
4. A direction perpendicular to the direction the plane wave moves
5. None of these/MORE than one of these/???
Note:
* Correct Answer: C
The electric field for a plane wave is given by:
$$\mathbf{E}(\mathbf{r},t) = \mathbf{E}_0e^{i(\mathbf{k}\cdot\mathbf{r} - \omega t)}$$
Suppose $\mathbf{E}_0$ points in the $+x$ direction.
Which direction is this wave moving?
1. The $x$ direction.
2. The radial ($r$) direction
3. A direction perpendicular to both $\mathbf{k}$ and $\mathbf{x}$
4. The $\mathbf{k}$ direction
5. None of these/MORE than one of these
Note:
* Correct Answer: D
A wave is moving in the $+z$ direction:
$$f(x, y, z, t) = Re\left[A e^{i(kz – \omega t + \delta)}\right]$$
The value of $f$ at the point $(0,0,z_0, t)$ and the point at $(x, y, z_0 , t)$ are related how?
$f_1 = f (0,0,z_0 , t)$ vs. $f_2 = f(x, y, z_0 , t)$
1. $f_1 = f_2$ always
2. $f_1 >$ or $<$ or $= f_2$ depending on the value of $x,y$
<img src="./images/two_points_plane_wave.png" align="center" style="width: 500px";/>
Note:
* Correct Answer: A
The electric field of an E/M wave is described by:
$$\mathbf{E} = E_0\sin\left(kx-\omega t\right)\hat{\mathbf{y}}$$
What is the direction of the magnetic field?
1. $+x$
2. $+y$
3. $–x$
4. $+z$
5. $-z$
Note:
* Correct Answer: D