Unit 16 Processes, exercise 1

a Read text A below. Mark the statements true (T) or false (F) according to the text.

  1. The process of absorbing heat from the sun is called solar radiation.
  2. If the average surface temperature of the Earth goes above 15°C, plants and animals might die.
  3. Half of the sun's solar radiation is reflected by clouds and the atmosphere.
  4. The heat from the Earth and clouds goes back into space.

A message or some feedback if needed.

b Rewrite the false statements so that they are true according to the text.

3. A quarter of the sun's solar radiation is reflected by clouds and the atmosphere.

A All the planets absorb heat from the sun in a process known as solar radiation. However, for life on our planet to continue, Earth must stay at an average surface temperature of around 15°C. For the Earth to stay at a constant temperature, it needs to absorb and emit radiation at the same rates.

As solar radiation travels to Earth, there is a series of steps which reduces the amount of radiation that reaches the surface:

  • Firstly, some is removed as it enters the atmosphere – the mixture of gases that surround our planet. Around 25% is then reflected by the upper atmosphere and clouds, while a further 20% is absorbed by them.
  • 5% of the radiation is reflected from the surface of the Earth – by deserts or ice.
  • Finally, 50% is absorbed by the Earth's surface.
  • Around 10% of this heat radiates from the surface, and the remaining 40% moves to the clouds and the atmosphere. This heat is then radiated back out into space, completing the cycle.

Adapted from: Johnson, K. (2016). GCSE Physics For You. (5th ed.). Oxford: Oxford University Press. p.214.