Radiation & Temperature Change (Edexcel GCSE Physics)

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Katie M

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Katie M

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Temperature of the Earth

Higher Tier Only

  • If the Earth had no atmosphere, the temperature on the surface would drop to about −180 °C at night, the same as the Moon’s surface at night
    • This would happen because the surface would be emitting all the radiation from the Sun into space

  • The temperature of the Earth is affected by factors controlling the balance between incoming radiation and radiation emitted
  • The Earth receives the majority of its heat in the form of thermal radiation from the Sun
    • At the same time, the Earth emits its own thermal radiation, with a slightly longer wavelength than the thermal radiation it receives (the surface temperature of the Earth is significantly smaller than the surface temperature of the Sun)

  • Some gases in the atmosphere, such as water vapour, methane, and carbon dioxide (greenhouse gases) absorb and reflect back longer-wavelength infrared radiation from the Earth and prevent it from escaping into space
    • These gases absorb the radiation and then emit it back to the surface

  • This process makes the Earth warmer than it would be if these gases were not in its atmosphere

greenhouse-effect, IGCSE & GCSE Physics revision notes

The Earth receives thermal radiation from the Sun but emits its own thermal radiation at the same time

  • The temperature of the Earth, therefore, depends on several factors, such as the rate that light and infrared radiation from the Sun are:
    • Reflected back into space
    • Absorbed by the Earth’s atmosphere or by the Earth’s surface
    • Emitted from the Earth’s surface and from the Earth’s atmosphere into space

The Greenhouse Effect

  • The rate of absorption and emission of radiation on Earth contributes to the Greenhouse Effect
    • This is the natural process that warms the Earth's surface from the Sun

  • The Sun's thermal radiation reaches the Earth's atmosphere where:
    • Some radiation is reflected back to space
    • Any radiation not reflected is absorbed and re-radiated by greenhouse gases

  • The absorbed radiation then warms the atmosphere and the surface of the Earth
    • This is similar to what happens in a greenhouse to keep a humid, and warm temperature to grow plants

edits-to-the-greenhouse-effect-new

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Katie M

Author: Katie M

Expertise: Physics

Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.