Calculate the ratio of the intensities of the reflected wave and the incident wave for a light wave incident normally on the surface of a deep body of water with index of refraction $n=1.33$.
Fresnel's equations give for light incident normally

$$
R=\frac{I_{\mathrm{r}}}{I_{\mathrm{i}}}=\left(\frac{n_{2}-n_{1}}{n_{2}+n_{1}}\right)^{2}=0.02 .
$$