Unit 16 Processes, exercise 1
a Read text A below. Mark the statements true (T) or false (F) according to the text.
b Rewrite the false statements so that they are true according to the text.
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.