E&M simple polarizability question

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In summary, the conversation discusses a homework problem regarding the atomic polarizability of a primitive model for an atom. The reference equation provided is used to find the electric field produced by the electron cloud at a certain distance from the center of the atom. The question then arises about the shift in the electron cloud and how it affects the electric field. The explanation is that the field becomes a dipole field, resulting in a change in the equation.
  • #1
iScience
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this is a homework problem i realized after posting it. so could a moderator please move this question to the homework section? thanks

one of Griffiths' example:

A primitive model for an atom consists of a point nucleus surrounded by a uniform charged spherical cloud of radius "a". Find the atomic polarizability of such an atom.

(reference equation):

$$\vec{p}=a \vec{E}$$
-------------------

First step:

the field (produced by the electron cloud) at distance d from the center of a uniformly charged sphere is

$$E_e=\frac{1}{4\pi \epsilon_0}\frac{qd}{a^3}$$

---------------so why is that the field produced by the shifted electron cloud?

ie, how does one go from

$$E_e=\frac{1}{4\pi \epsilon_0}\frac{q}{a^2}$$

to..

$$E_e=\frac{1}{4\pi \epsilon_0}\frac{qd}{a^3}$$

(where "d" and "a" are not equal)?
 
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  • #2
It's a dipole field.
 

1. What is polarizability in the context of E&M?

Polarizability is a measure of the ability of a material to become polarized when subjected to an electric field. It is a property that describes how easily the charges within a material can be redistributed in response to an external electric field.

2. How is polarizability related to simple harmonic motion in E&M?

In E&M, simple harmonic motion refers to the oscillation of charges within a material in response to an electric field. The polarizability of a material determines the strength and frequency of this oscillation, as well as the resulting electric dipole moment.

3. What factors affect the polarizability of a material?

The polarizability of a material is affected by several factors, including the electronic structure of the material, the strength of the electric field, and the temperature. Generally, materials with more loosely bound electrons and lower melting points tend to have higher polarizabilities.

4. How is polarizability different from conductivity?

Polarizability and conductivity are two different properties of materials in E&M. While polarizability describes the ability of a material to become polarized in response to an electric field, conductivity refers to the material's ability to conduct electricity. In general, materials with higher polarizabilities tend to have lower conductivities.

5. How is polarizability measured in experiments?

Polarizability can be measured through various experimental techniques, such as measuring the induced dipole moment in an electric field or observing the change in refractive index of a material in an electric field. The resulting data can then be used to calculate the polarizability of the material.

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