Final answer:
Mirages are formed due to refraction in hot air creating temperature layers. Therefore, the correct option is d.
Step-by-step explanation:
Mirages occur in deserts when there is a hot layer of air near the ground. This hot air has a lower refractive index than the cooler air above it. When light from faraway objects passes through these temperature layers, it undergoes refraction. The bending of light at different angles due to the varying refractive index creates an optical illusion, making it seem as though the light is coming from a pool of water on the ground.
This phenomenon is a result of the temperature-dependent refractive index causing the light rays to curve, creating the appearance of a reflective surface that isn't actually present.
Total internal reflection, dispersion, and reflection from the ground are not the primary mechanisms involved in the formation of mirages. While total internal reflection and dispersion play roles in some optical phenomena, the specific conditions in a desert environment, with temperature-dependent refractive index variations, lead to the refraction of light being the dominant factor in mirage formation.
Therefore, option (d) correctly explains the process underlying the creation of mirages in hot air.