- #1
Palindrom
- 263
- 0
Hey everyone,
I'm having some trouble understanding this, any help would be appreciated:
Calculate the density of states for a free particle with momentum [tex]\[
\hbar k
\]
[/tex] for the angles between [tex]\[
\left[ {\theta _0 ,\theta _0 + d\theta } \right]
\]
[/tex] relative to an electric field [tex]\[
\vec \varepsilon
\]
[/tex], in the ultra-relative limit [tex]\[
E \cong pc
\]
[/tex].
In my solutions, the first thing they do is to say: Well, as usual, first find [tex]\[
N\left( E \right)
\]
[/tex] and then take the derivative with respect to [tex]\[
E
\]
[/tex], but that's OK. The problem is how they calculate [tex]\[
N\left( E \right)
\]
[/tex]:
[tex]\[
N\left( E \right) = \frac{V}{{h^3 }}\int\limits_{\theta \in \left[ {\theta _0 ,\theta _0 + d\theta } \right]} {d^3 p} = \frac{V}{{h^3 }}2\pi \sin \left( {\theta _0 } \right)d\theta \int\limits_0^{p_{\max } } {p^2 d^2 p}
\]
[/tex]
I can live with the first move. But I don't understand where this sine comes from, or [tex]\[
2\pi
\]
[/tex], and that other integral... help?
Thanks in advance!
I'm having some trouble understanding this, any help would be appreciated:
Calculate the density of states for a free particle with momentum [tex]\[
\hbar k
\]
[/tex] for the angles between [tex]\[
\left[ {\theta _0 ,\theta _0 + d\theta } \right]
\]
[/tex] relative to an electric field [tex]\[
\vec \varepsilon
\]
[/tex], in the ultra-relative limit [tex]\[
E \cong pc
\]
[/tex].
In my solutions, the first thing they do is to say: Well, as usual, first find [tex]\[
N\left( E \right)
\]
[/tex] and then take the derivative with respect to [tex]\[
E
\]
[/tex], but that's OK. The problem is how they calculate [tex]\[
N\left( E \right)
\]
[/tex]:
[tex]\[
N\left( E \right) = \frac{V}{{h^3 }}\int\limits_{\theta \in \left[ {\theta _0 ,\theta _0 + d\theta } \right]} {d^3 p} = \frac{V}{{h^3 }}2\pi \sin \left( {\theta _0 } \right)d\theta \int\limits_0^{p_{\max } } {p^2 d^2 p}
\]
[/tex]
I can live with the first move. But I don't understand where this sine comes from, or [tex]\[
2\pi
\]
[/tex], and that other integral... help?
Thanks in advance!