On a hot summer night, the refractive index of air is smallest near the ground and increases 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

$\begin{array}{1 1} \text{bends upwards} \\ \text{becomes narrower} \\ \text{goes horizontally without any deflection } \\ \text{bends downwards } \end{array}$