A small bulb sits at the bottom of a pond of clear water, $2.0\ \text{m}$ below the surface. The refractive index of water is $4/3$. Seen from above, light comes out of the water only through a bright circle on the surface, as shown in the figure. The radius of this circle is closest to

Fig. 1: A bulb at the bottom of a pond 2.0 m deep. The rays that meet the surface at the critical angle C mark the edge of a bright circle of radius r.