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16 changes: 16 additions & 0 deletions content/maxwell1_fundamentals/appendix/appendix_index.rst
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@@ -0,0 +1,16 @@
.. _maxwell1_appendix_index:

Appendix
========

Here, supplementary derivations and content relevant to *Maxwell 1: Fundaments* is provided.

**Contents**

.. toctree::
:maxdepth: 1

wave_eq_derivation
totalrefl_and_brewsterangl


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@@ -1,16 +1,16 @@
.. _totalrefl_and_brewsterangl:

Total reflection and Brewster angle
===================================
Total Reflection and Brewster's Angle
=====================================

.. purpose::

We first identify total reflection and brewster angle for a dielectric media, then relate them to conductive medium.

Total reflection
Total Reflection
----------------

For a perfect dielectric, the conductivity is zero and the permeability is that of free space that is, :math:`\mu_1=\mu_2=\mu_0`. Snell's law of refraction shown in :ref:`snells_law` with the setup shown in :numref:`snellslaw_setup` then reduces to
For a perfect dielectric, the conductivity is zero and the permeability is that of free space that is, :math:`\mu_1=\mu_2=\mu_0`. In this case, Snell's law reduces to:

.. math::
\frac{\text{sin} \theta_i}{\text{sin} \theta_t} = \frac{k_1}{k_2} = \Big(\frac{\epsilon_2}{\epsilon_1}\Big)^{1/2} = n_{12}
Expand All @@ -26,8 +26,8 @@ where :math:`n_{12}` is the relative index of refraction. If :math:`\epsilon_2 >
Tranmission angle :math:`\theta_t` as a function of the incident angle :math:`\theta_i` when :math:`\sigma_1` = 1 S/m and :math:`\sigma_2` = 0.1 S/m. Magnetic permeability and dielectric permittivitivy assumed to be those of free-space (:math:`\epsilon = \epsilon_0` and :math:`\mu = \mu_0`)


Brewster angle
--------------
Brewster's Angle
----------------

From derived reflection coefficients for TE mode in :ref:`fresnel_equations`, the reflection coefficient for perfect dielectric can be written as

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@@ -1,36 +1,28 @@
.. _maxwell1_looking_for_more:
.. _maxwell1_appendix_wave_eq_derivation_time:

Looking for more?
=================
Derivation of the Wave Equation in Time
=======================================

.. _time_domain_equations_details:
Here, we derive the wave equations in time for the electric and magnetic fields.To accomplish this, we begin with :ref:`Faraday's Law <faraday>` and :ref:`Ampere-Maxwell's Law <ampere_maxwell>`:

Maxwell's equations in time
---------------------------
.. include:: ../../equation_bank/faraday_time.rst

To derive the wave equations in the time domain, we begin with :ref:`Faraday's
Law <faraday>` and :ref:`Ampere-Maxwell's Law <ampere_maxwell>`:
.. include:: ../../equation_bank/ampere_maxwell_time.rst

.. include:: ../equation_bank/faraday_time.rst
as well as the three constitutive relations:

.. include:: ../equation_bank/ampere_maxwell_time.rst

and the three constitutive relations:

.. include:: ../equation_bank/ohms_law_time.rst
.. include:: ../../equation_bank/ohms_law_time.rst

.. math:: \mathbf{d} = \epsilon \mathbf{e}
:name: depse

.. math:: \mathbf{b} = \mu \mathbf{h}
:name: bmuh

The derivations will be done for first :math:`\mathbf{e}` and then for :math:`\mathbf{h}`.
Derivation for the Electric Field
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Derivation for electric field
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

To derive the wave equation which uses only :math:`\mathbf{e}`, we first take
To derive the wave equation for :math:`\mathbf{e}`, we first take
the curl of Faraday's Law, shown in equation :eq:`faraday_time`:

.. math:: \boldsymbol{\nabla} \times (\boldsymbol{\nabla} \times \mathbf{e}) = - \boldsymbol{\nabla} \times \frac{\partial \mathbf{b}}{\partial t}
Expand All @@ -43,7 +35,7 @@ The appropriate constitutive relations can be substituted into Equation
.. math:: \boldsymbol{\nabla} \times \boldsymbol{\nabla} \times \mathbf{e} = - \boldsymbol{\nabla} \times \left ( \frac{\partial}{\partial t} (\mu \mathbf{h}) \right )
:name: hme2

Because we assume a homogenous space, the physical properties :math:`\mu`,
Assuming the physical properties are homogeneous throughout the domain, :math:`\mu`,
:math:`\epsilon`, and :math:`\sigma` can be moved out front of the derivative
terms. This simplifies the above expressions:

Expand Down Expand Up @@ -86,11 +78,11 @@ into :eq:`hme5`, we get the following expression:

This is the wave equation for the electric field in the time domain.

Derivation for magnetic field
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Derivation for the Magnetic Field
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

To derive the wave equation for :math:`\mathbf{h}`, we repeat the above
derivation but now start with taking the curl of Ampere's Law, shown in
derivation but start by taking the curl of Ampere's Law, shown in
equation :eq:`ampere_maxwell_time`:

.. math:: \boldsymbol{\nabla} \times (\boldsymbol{\nabla} \times \mathbf{h}) = \boldsymbol{\nabla} \times \mathbf{j} + \boldsymbol{\nabla} \times \frac{\partial \mathbf{d}}{\partial t}
Expand Down Expand Up @@ -139,74 +131,6 @@ into the wave equation. The following shows these derivations.
.. math:: \boldsymbol{\nabla}^2 \mathbf{h} - \epsilon \mu \frac{\partial^2 \mathbf{h}}{\partial t^2} - \sigma \mu \frac{\partial \mathbf{h}}{\partial t} = 0
:name: hmh6

Equation :eq:`hmh6` is then the wave equation for the magnetic field in the tim domain.

Summary
^^^^^^^

We now have two wave equations or second-order differential equations; one for
the electric field and one for the magnetic field, summarized in Equations
:eq:`hme7` and :eq:`hmh7`.

.. math:: \boldsymbol{\nabla}^2 \mathbf{e} - \mu \sigma \frac{\partial \mathbf{e}}{\partial t} - \mu \epsilon \frac{\partial^2 \mathbf{e}}{\partial t^2} = 0
:name: hme7

.. math:: \boldsymbol{\nabla}^2 \mathbf{h} - \mu \sigma \frac{\partial \mathbf{h}}{\partial t} - \mu \epsilon \frac{\partial^2 \mathbf{h}}{\partial t^2} = 0
:name: hmh7

Solving the wave equation when :math:`\sigma=0`
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

In the case where :math:`\sigma` is zero, Equations :eq:`hme7` and :eq:`hmh7` become:

.. math:: \boldsymbol{\nabla}^2 \mathbf{e} - \mu \epsilon \frac{\partial^2 \mathbf{e}}{\partial t^2} = 0
:name: hme13

.. math:: \boldsymbol{\nabla}^2 \mathbf{h} - \mu \epsilon \frac{\partial^2 \mathbf{h}}{\partial t^2} = 0
:name: hmh14

The following derivation will be the same for both the magnetic and electric
fields. Let's use the magnetic field for this analysis. In 1D, Equation
:eq:`hmh14` is now written as:

.. math:: \frac{\partial^2 \mathbf{h}}{\partial z^2} = \mu \epsilon \frac{\partial^2 \mathbf{h}}{\partial t^2},
:name: hmh15

for which there is a solution of the form:

.. math:: \mathbf{h} = \mathbf{h}_0 \cos \left ( 2\pi \frac{z-vt}{\lambda} \right ),
:name: slwave

where :math:`v` is the speed of the sinosoidal wave and :math:`\lambda` is its
wavelength. We can check this solution by taking the derivatives with respect
to :math:`z` and :math:`t` to see if we get back to Equation :eq:`hmh15`.

.. math:: \frac{\partial^2 \mathbf{h}}{\partial z^2} = \frac{\partial}{\partial z} \left [ - \mathbf{h}_0 \sin \left( 2\pi \frac{z-vt}{\lambda} \right) \left( \frac{2\pi}{\lambda}\right) \right ] = - \mathbf{h}_0 \cos \left( 2\pi \frac{z-vt}{\lambda} \right) \left( \frac{2\pi}{\lambda}\right)^2

.. math:: \frac{\partial^2 \mathbf{h}}{\partial t^2} =\frac{\partial}{\partial t} \left [ - \mathbf{h}_0 \sin \left ( 2\pi \frac{z-vt}{\lambda} \right ) \left ( \frac{-2\pi v}{\lambda} \right) \right ] = - \mathbf{h}_0 \cos \left ( 2\pi \frac{z-vt}{\lambda} \right ) \left ( \frac{-2\pi v}{\lambda} \right)^2

We now substitude these solutions into Equation :eq:`hmh15` and simplify:

.. math:: \left (\frac{2\pi}{\lambda} \right)^2 = \epsilon \mu \left (\frac{-2\pi v}{\lambda} \right)^2

.. math:: 1 = \epsilon \mu v^2

.. math:: v = \sqrt{\frac{1}{\epsilon \mu}}
:name: v

This shows that the solution to Equation :eq:`hmh15` is a wave of the form
given in Equation :eq:`slwave` if Equation :eq:`v` holds true. In free space,
we can quickly evaluate Equation :eq:`v`, knowing that :math:`\mu = 4\pi
\times 10^{-7} \frac{T \cdot m}{A}` and :math:`\epsilon = 8.85 \times 10^{-12}
\frac{F}{m}`:

.. math:: v = \sqrt{\frac{1}{( 4\pi \times 10^{-7})(8.85 \times 10^{-12})}} = 3 \times 10^8

The units of :math:`v` work out as following:

.. math:: \sqrt{ \frac{1}{\left[\frac{T \cdot m}{A} \right] \left [ \frac{F}{m} \right ]} } = \left ( \frac{A}{T \cdot F} \right) ^ {1/2} = \left ( \frac{\frac{C}{s}}{\frac{V\cdot s}{m^2} \cdot F} \right) ^ {1/2} =
Equation :eq:`hmh6` is then the wave equation for the magnetic field in the time domain.

.. math:: \left ( \frac{\frac{F \cdot V}{s}}{\frac{V\cdot s}{m^2} \cdot F} \right) ^ {1/2} = \left ( \frac{F\cdot V}{s} \frac{m^2}{V \cdot F \cdot s} \right ) ^{1/2} = \frac{m}{s}

Thus, the velocity of the wave is :math:`3 \times 10^8` m/s, which is the
speed of light! The same derivation can be done using the electric field.
Original file line number Diff line number Diff line change
Expand Up @@ -10,48 +10,7 @@ Visualization of the Electromagnetic Fields
By completing this exercise, you will become comfortable with the numerical modeling tools provided and gain a fundamental understanding of the fields which are caused by a harmonic electrical current dipole.



Introduction
------------

Here, we will show you how to use the widget and walk you through some research questions.



**Getting Started**

Within the jupyter notebook, there are 3 tools:


.. figure:: images/E_source_widget_geometry.png
:align: right
:figwidth: 50%
:name: widget_geometry

Visualization of problem geometry in 3D.


**Step 1: Choosing Geometric Parameters**

These toggles allow the user to adjust the problem geometry and visualize it in 3D.
Relative to the source dipole, the user may specify observation locations on a profile line or comprising a plane.
An example of the problem geometry is shown on the right.


**Step 2: Visualizing the Fields**

These toggles allow the user to change physical parameters relevant to the problem and visualize different components of the electric field, magnetic field and current density.
As any of the physical parameters or plotting parameters are changed, the fields are automatically plotted on the profile line and plane defined in Step 1.
An example of the fields on a profile line and on a plane is shown below.


.. figure:: images/E_source_plane_example.png
:align: center
:figwidth: 100%
:name: field_example

Visualization of the fields. (Left panel) Vector plot of :math:`E_x` at locations on a plane. (Right panel) In-phase component of :math:`E_x` along a profile line.

**Link to the modeling app**

Research Questions
------------------
Expand Down
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Expand Up @@ -13,6 +13,8 @@ Dipole Sources in Homogeneous Media
- Asymptotic expressions are provided for several cases.
- Numerical modeling tools are made available for investigating the dependency of the electric and magnetic fields on various parameters.

**Introduction**

Dipole sources are fundamental electromagnetic sources which exist at a single point in space.
Although true dipole sources do not exist in nature, they do very well at approximating the electromagnetic sources used for many geophysical applications.
In geophysics, there are two types of dipole sources: electrical current dipole sources and magnetic dipole sources.
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -10,31 +10,7 @@ Visualization of the Electromagnetic Fields
By completing this exercise, you will become comfortable with the numerical modeling tools provided and gain a fundamental understanding of the fields which are caused by a harmonic magnetic dipole.



Introduction
------------

Here, we will show you how to use the widget and walk you through some research questions.



**Getting Started**

Within the jupyter notebook, there are 3 tools:

**Step 1: Choosing Geometric Parameters**

These toggles allow the user to adjust the problem geometry and visualize it in 3D.
Relative to the source dipole, the user may specify observation locations on a profile line or comprising a plane.
An example of the problem geometry is shown on the right.


**Step 2: Visualizing the Fields**

These toggles allow the user to change physical parameters relevant to the problem and visualize different components of the electric field, magnetic field and current density.
As any of the physical parameters or plotting parameters are changed, the fields are automatically plotted on the profile line and plane defined in Step 1.
An example of the fields on a profile line and on a plane is shown below.

**Link to the app**

Research Questions
------------------
Expand Down Expand Up @@ -68,24 +44,20 @@ Now slowly increase the frequency by factors of 10. When you reach 1000 Hz, noti

**The Inductive Response:**

According to `Faraday's law<faraday>`, the effects of EM induction increase as frequency increases. Set the conductivity to 0.1 S/m and choose a point (x,y,z) = (40m, 0m, 0m). Examine the x,y and z components of the electric and magnetic fields.
According to :ref:`Faraday's law<faraday>`, the effects of EM induction increase as frequency increases. Set the conductivity to 0.1 S/m and choose a point (x,y,z) = (40m, 0m, 0m). Examine the x,y and z components of the electric and magnetic fields.

- At what frequency do the effects of EM induction become significant?
- Now increase the background conductivity to 1 S/m and examine the same location. At what frequency do the effects of EM induction become significant?
- Now choose a location closer to the dipole source (x,y,z) = (10m, 0m, 0m). At what frequency do the effects of EM induction become significant compared to the primary field?

**Magnetic Permeability and Dielectric Permittivity**

Set the log-conductivity to .

Set the log-conductivity to 0.01 S/m.

- Try increasing the relative permeability (:math:`\mu_r`). Do you notice any significant changes in the shape and amplitude of the electric and magnetic fields?
- Now try increasing the relative permittivity (:math:`\varepsilon_r`). When you do this at low frequencies, do you notice any significant changes in the shape and amplitude of the electric and magnetic fields? How about when you do this at high frequencies?


.. **Hypothetical Scenario 1:**

.. *I put this here in case we wanted to make a hypthetical scenario where these equations could be used to solve a practical problem.*



Expand Down
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@@ -1,7 +1,7 @@
.. _fundamental_laws_details:
.. _fundamental_laws_coulomb:

Details
=======
Gauss's Law from Coulomb's Law
==============================


.. _gauss_electric_equivalence_to_coulombs_law:
Expand Down
62 changes: 49 additions & 13 deletions content/maxwell1_fundamentals/formative_laws/gauss_electric.rst
Original file line number Diff line number Diff line change
Expand Up @@ -78,22 +78,58 @@ integrands, giving the differential form of Gauss's law:
It can be shown that Gauss' law for electric fields is equivalent to Coulomb's
law (see :ref:`gauss_electric_equivalence_to_coulombs_law`)

Gauss's Law in Matter
---------------------

Gauss's law for electric fields is most easily understood by neglecting :ref:`electric displacement<dielectric_permittivity_index>` (:math:`\mathbf{d}`). In matter, the :ref:`dielectric permittivity<dielectric_permittivity_index>` may not be equal to the permittivity of free-space (i.e. :math:`\varepsilon \neq \varepsilon_0`). In matter, the density of electric charges can be separated into a "free" charge density (:math:`\rho_f`) and a "bounded" charge density (:math:`\rho_b`), such that:

.. math::
\rho = \rho_f + \rho_b
:label: gauss_law_charge_decomp

The free-charge density refers to charges which flow freely under the application of an electric field; i.e. they produce a current which is divergence-free. The bounded-charge density refers to electrical charges attributed to electrical polarization (:math:`\mathbf{p}`). By combining Eqs. :eq:`Gauss_e_diff` and :eq:`gauss_law_charge_decomp` with our definition for :ref:`electrical polarization<dielectric_permittivity_index>`, we find that:

.. math::
\nabla \cdot \mathbf{d} - \nabla \cdot \mathbf{p} = \rho_f + \rho_b
:label:

By using the constitutive relationship :math:`\mathbf{d} = \varepsilon \mathbf{e}` and separating the previous equation into bounded and free contributions, we find that:

.. math::
-\nabla \cdot \mathbf{p} = \rho_b
:label:

and

.. math::
\nabla \cdot \mathbf{d} = \rho_f
:label:

The above equation is the **differential form of Gauss's equation in matter**. Meanwhile, the **integral form of Gauss's equations in matter** is given by:

.. math::
\int_V \nabla \cdot \mathbf{d} \; dV = \oint_S \mathbf{d} \cdot \mathbf{\hat n} \; da = Q_f

where :math:`Q_f` is the total enclosed free charge.

Units
-----

+-----------------------+---------------------+------------------------------------+---------------------------------------+
| Surface area | :math:`\text{S}` | :math:`\text{m}^{2}` | Square meter |
+-----------------------+---------------------+------------------------------------+---------------------------------------+
| Volume | :math:`V` | :math:`\text{m}^{3}` | Cubic meter |
+-----------------------+---------------------+------------------------------------+---------------------------------------+
| Electric charge | :math:`\text{q, Q}` | :math:`\text{C}` | Coulomb |
+-----------------------+---------------------+------------------------------------+---------------------------------------+
|Electric charge density| :math:`\rho` |:math:`\frac{\text{C}}{\text{m}^3}` | Coulomb per cubic meter |
+-----------------------+---------------------+------------------------------------+---------------------------------------+
| Electric field | :math:`\mathbf{e}` |:math:`\frac{\text{V}}{\text{m}}` | Volt per meter |
+-----------------------+---------------------+------------------------------------+---------------------------------------+
|Electrical permittivity|:math:`\varepsilon_0`| :math:`\frac{\text{F}}{\text{m}}` | Farad per meter |
+-----------------------+---------------------+------------------------------------+---------------------------------------+
+-----------------------+-----------------------------+---------------------+-------------------------+
| Surface area | :math:`\text{S}` | m :math:`\! ^{2}` | Square meter |
+-----------------------+-----------------------------+---------------------+-------------------------+
| Volume | :math:`V` | m :math:`\! ^{3}` | Cubic meter |
+-----------------------+-----------------------------+---------------------+-------------------------+
| Electric charge | :math:`q, Q, Q_f` | C | Coulomb |
+-----------------------+-----------------------------+---------------------+-------------------------+
|Electric charge density| :math:`\rho, \rho_f, \rho_b`| C/m :math:`\! ^{3}` | Coulomb per cubic meter |
+-----------------------+-----------------------------+---------------------+-------------------------+
| Electric field | :math:`\mathbf{e}` | V/m | Volt per meter |
+-----------------------+-----------------------------+---------------------+-------------------------+
|Electric displacement | :math:`\mathbf{d}` | A/m :math:`\! ^{2}` | Volt per meter |
+-----------------------+-----------------------------+---------------------+-------------------------+
|Dielectric permittivity|:math:`\varepsilon` | F/m | Farad per meter |
+-----------------------+-----------------------------+---------------------+-------------------------+

**Conversions**

Expand Down
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