Question

The cause of mirage formation in desert areas is

• A. The refractive index of atmosphere decreases with decrease in height
• B. The refractive index of atmosphere increases with decrease in height
• C. The refractive index of atmosphere does not change with height
• D. Scattering

Answer 1

The correct option is B The refractive index of atmosphere increases with decrease in height

The reason for mirage formation is "The refractive index of atmosphere increases with decrease in height" and hence the rays get totally refracted and forms a mirage.

As we go down in the atmosphere, the air gets denser and hence the velocity in that medium decreases. Since refractive index $\mu =\frac{c}{v}$. Hence, the refractive index increases as we decrease height.