6.3

Question 1

What is black body radiation?

Answer 1

An object that absorbs all radiation on it (none transmitted or reflected) and is the best possible emitter.

Question 2

Describe how the temperature of an object depends on the balance between radiation absorbed and radiation emitted.

Answer 2

• If an object is hotter than its surrounding, it will emit more radiation that it absorbs - decrease in temperature (e.g. coffee in cup) .
• If an object is cooler than its surrounding, it will absorb more radiation than it emits - increase in temperature (e.g. burgers on grill).
• If an object is at constant radiation, it is emitting radiation at the same rate as absorbing radiation.

Question 3

[Describe how to] Interpret diagrams to show how radiation affects the temperature of the Earth’s surface and atmosphere.

Answer 3

• Short wavelength radiation travels from Sun to Earth.
• Some is reflected (e.g. by clouds)
• The rest is absorbed by the Earth’s surface, and so it emits infrared radiation back.
• Some energy of infrared that is emitted from Earth trapped by green house gases in atmosphere

Question 4

What are examples of factors which determine the temperature of the Earth.

Answer 4

• Cloudy: the more clouds, the hotter the Earth as more infrared radiation emitted from is is reflected back.
• Pollution: the more pollution, the more green house gases which reflect infrared radiation emitted by Earth back.