Radiation & Temperature Change Flashcards

All 7 cards in this deck

What must be true of the radiation for a body to stay at a constant temperature?

It must radiate the same average power that it absorbs (power out = power in).

What happens to a body if the average power it absorbs is greater than the average power it radiates?

e.g. a lamp just after being switched on

Its temperature rises. The lamp heats up until it radiates power at the same rate as it is supplied, then stays at a constant temperature.

What happens to a body if the average power it radiates is greater than the average power it absorbs?

Its temperature falls (the body cools).

True or false? A body sitting at a constant temperature is emitting no radiation.

False. It is radiating, but at the same average power as it absorbs, so its temperature does not change.

What controls the average temperature of the Earth?

The balance between the average power of radiation absorbed from the Sun and the average power radiated back out into space.

What effect do greenhouse gases in the atmosphere have on the Earth's temperature?

They absorb infrared radiation emitted by the Earth and re-radiate some back to the surface, so less power escapes and the temperature rises.

What effect does a pale, reflective surface such as ice or cloud have on the Earth's temperature?

It reflects more of the incoming solar radiation, so less is absorbed and the temperature is lower.