Role of Atmosphere: Introduction of Atmosphere, Functions, and Importance of Atmosphere (For CBSE, ICSE, IAS, NET, NRA 2022)

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Introduction to Atmosphere

  • Atmosphere can be defined as the envelope of gases surrounding the earth or another planet.
  • It consists of physical mixture of gases and particle matter.
  • It acts as a protective layer that safeguards the earth from the harsh conditions of the solar system.
    • Harmful ultraviolet and infrared rays of the Sun.
  • The layers get thinner at higher altitudes.
Structure of Earth

Functions and Importance of Atmosphere

  • Atmosphere helps in protecting the earth from the radiations and cosmic rays.
  • The ozone layer protects the earth from the harmful ultraviolet radiations.
  • It protects us from meteorites.
  • It is also responsible for regulation of daily temperatures, night, and day.
  • It allows the light energy to reach the surface of earth and ocean.
  • It protects materials from the outer space to enter earth.
  • It further helps in retaining the necessary warmth on the earth and helps in the circulation of water vapour.
Layers of Atmosphere

Temperature and Speed of Sound

  • Temperature decreases with altitude starting at sea level.
  • The temperature increases with height in the stratosphere starting above about 20 km.
  • The speed of sound depends only on temperature and not on the gas pressure or density due to an ideal gas of constant composition.

Optical Properties

Scattering

  • The photons interact with the atmosphere through scattering when light passes through Earth՚s atmosphere.
  • Indirect radiation is light that has been scattered in the atmosphere.
  • One of the examples is that of Rayleigh scattering where shorter (blue) wavelengths scatter more easily than longer (red) wavelengths.

Absorption

  • The energy of the molecule gets increased the moment it absorbs a photon.
  • O2 and O3 absorb all wavelengths shorter than 300 nanometers.
  • Infrared and radio windows transmit some infrared and radio waves at longer wavelengths.
    • One of the examples is the radio window runs from about one centimeter to about eleven-meter waves.

Emission

  • It occurs when an object emits radiation.
  • Depending on their “black body” emission curves, objects tend to emit amounts and wavelengths of radiation.
  • Colder objects emit less radiation, with longer wavelengths.
  • On clear nights Earth՚s, surface cools down faster than on cloudy nights.

Refractive Index

  • The refractive index of air is close to, but just greater than one.
  • The systematic variations in refractive index can lead to the bending of light rays over long optical paths.
  • The refractive index of air depends on temperature.
    • Gives rise to refraction effects when the temperature gradient is large.
    • Mirage is an example.

FAQs

Q 1. What is an Atmosphere?

Answer: Atmosphere can be defined as the envelope of gases surrounding the earth or another planet.

Q 2. What are some of the important functions of the Atmosphere?

Answer:

Some of the important functions of the Atmosphere are:

i) The ozone layer protects the earth from the harmful ultraviolet radiations.

ii) It protects us from meteorites.

iii) It protects materials from the outer space to enter earth.

Q 3. What are the five different layers present in Atmosphere?

Answer:

Five different layers of Atmosphere are:

i) Troposphere

ii) Stratosphere

iii) Mesosphere

iv) Thermosphere

v) Exosphere

Q 4. Why the speeds of sound depend on temperature and not on gas?

Answer: The speed of sound depends only on temperature and not on the gas pressure or density due to an ideal gas of constant composition.

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