Eduprobe
Question:
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 bends upwards.
bends downwards
goes horizontally without any deflection
bends upwards
becomes narrower
Solution:
Every point on the horizontal ray of light behaves as a source of light. Thus the secondary rays which are directed towards denser medium would bend towards the normal. This phenomena causes the bending of the rays upwards.