Question

(a) Explain briefly what is meant by atmospheric pressure, and why it decreases with altitude.

(b) Explain the role of the Earth’s magnetosphere in protecting the atmosphere from solar wind, and in creating the auroras.

(c) Why is the sky blue? Would you expect to see blue skies on other planets?

Answer 1

The pressure at any point on Earth is the weight of the molecules of air per area exerted by the air above that point.

As we move up along the atmosphere the amount of air column present above our location starts reducing so the weight of air molecules starts reducing and the atmospheric pressure reduces.

b) Auroras and solar winds basically consist of a stream of charged particles which includes protons, electrons and alpha particles. these charged particles coming from Sun travel towards Earth. The earth's magnetic field deflects these charged particles and protects or shield Earth's surface.

c) The sky is blue due to the phenomenon of scattering of light. As per Rayleigh scattering, the light with the lower wavelength (Blue has the lowest wavelength in visible light) undergoes maximum scattering and light with large wavelength undergoes least scattering.Blue colour scatters most and red the least. When Sunlight enters atmosphere blue light is almost completely scattered in the sky and so the sky appears blue.

However, on other planets or space, we do not have an atmosphere so there are no molecules of air to scatter light so the sky in space or other planets seems dark instead of blue.