On a hot summer night, the refractive index of air is smallest near the ground and increase with height from the ground . when a light beam is directed horizontally, the Huygen's principle leads us to conclude that as it travels, the light beam:

Question

$\begin{array}{1 1} \text{goes horizontal without any deflection} \\ \text{bends down wards} \\\text{bends upwards}\\ \text{become narrower} \end{array} $