Answer
0 to 12cm
Work Step by Step
First we consider equation (34-8):
$\frac{n_1}{p}+\frac{n_2}{i}=\frac{n_2-n_1}{r}$
where $n_1=1.0$ because we assume normal air around the glass rod.
As $i$ approaches negative infinity, we can write:
$\frac{n_1}{p}+\frac{n_2}{-\infty}=\frac{n_2-n_1}{r}$
$\frac{n_1}{p}=\frac{n_2-n_1}{r}$
Solving for $p$, we obtain:
$p=n_1(\frac{n_2-n_1}{r})^{-1}$
$p=1.0(\frac{1.5-1.0}{6.0cm})^{-1}$
$p=12cm$
Therefore the object distance can be anywhere from 0 to 12cm.
