I find money in the jar

To solve the problem, we use Snell's law which states:

$\frac{sin\theta_{1}}{sin\theta_{2}}=\frac{n_{2}}{n_{1}}$

where, $\theta_{1}$ and $\theta_{2}$ are angle of incident and refraction (with normal), and $n_{1}$ and $n_{2}$ , the refractive indices of the two media respectively.

Now, $sin\theta_{1}= \frac {8}{\sqrt{h^{2}+8^{2}}}$ , $sin\theta_{2}= \frac {4}{\sqrt{h^{2}+4^{2}}}$ , $n_{1}=n_{air}=1$ , and $n_{2}=n=1.333$ .

Therefore, $\frac{sin\theta_{1}}{sin\theta_{2}}=\frac{n_{2}}{n_{1}}$

$\Rightarrow\frac{8}{\sqrt{h^{2}+8^{2}}}\times\frac{\sqrt{h^{2}+4^{2}}}{4}=\frac{1.333}{1}\Rightarrow\frac{2\sqrt{h^{2}+16}}{\sqrt{h^{2}+64}}=1.333$ $\Rightarrow 4(h^{2}+16) = 1.333^{2}(h^{2}+64)\Rightarrow 2.22h^{2} = 49.720896$ $\Rightarrow h^{2} =22.36545814\Rightarrow h =4.729213268\approx \boxed{4.73} cm$