# Extensivity of an Ideal Solid

1. Nov 1, 2012

### cstang52

$\frac{}{}$1. The problem statement, all variables and given/known data
Starting from S(E,N)=c(N)+3Nk[1+LN($\frac{E}{3Nh\nu}$)], derive a version of the Entropy, S(E,N) of an ideal solid that is extensive, that is, for which S($\lambda$E,$\lambda$N)=$\lambda$S(E,N)

2. Relevant equations

3. The attempt at a solution
Basically have to prove that S($\lambda$E,$\lambda$N)=$\lambda$S(E,N).

I can set it up, but I don't know how to eliminate terms to get to a form I can work with.

2. Nov 1, 2012

### cstang52

I have it setup like this:

S(λ E,λ N)=λ S(E,N)

c(λN)+3(λN)k[1+ln$\frac{λE}{3(λN)h\nu}$]=λ{c(N)+3Nk[1+ln$\frac{E}{3Nh\nu}$]

But 1. I dont know how to reduce the left side, and
2. when I distribute λ through the right side, is it on everything ending up looking like this: c(λN)+λ(3Nk)[λ+ln$\frac{λE}{λ(3Nh\nu)}$]? Or something else...

3. Nov 1, 2012

### haruspex

There's one too many lambdas in there:
$c(λN)+λ(3Nk)[1+ln\frac{λE}{λ(3Nh\nu)}]$