# Homework Help: KELVIN scale-Can't make sense of the last step of this solution

1. Oct 24, 2008

I do not understand how they went from $\ln T_c-\lnT_H=\theta_c-\theta_H$
to
$\theta=\ln T+C$

Why did the subscripts drop out? What just happened?

2. Oct 25, 2008

### physicsnoob93

exp means e^thethac if that is thetha

so you get e^(thethac-thethah) is Tc/Th.

If you ln both sides, you'll get ln(Tc/Th) = lnTc-lnTh and on the other side lne^(thethac-thethah) = (thethac-thethah)lne. lne is one.

Thus

lnTc-lnTh = thethac-thethah

3. Oct 25, 2008

### HallsofIvy

"C" and "H" just represent different measurements of the temperature. Since you take TH to be a fixed temperature, that just leaves one temperature- you don't need the "C" to distinguish it form "H".

4. Oct 26, 2008