Paper 1 - Temperature And Radiation Flashcards
How does radiation emitted by a body depend on its temperature ?
The intensity of radiation emitted by an object increases as its temperature increases. The wavelengths of the radiation emitted also change with temperature - the higher the temperature the shorter the wavelength
When do objects emit EM radiation ?
All objects above absolute zero will emit electromagnetic radiation. Their temperature will depend on how much of it they absorb and how much of it they radiate.
What factors affect temperature
- a body at a constant temperature absorbs the same amount of radiation it emits.
- an object will increase its temperature if it absorbs more radiation than it emits as the temp of a body increases more energetic radiation is emitted including infrared, visible and UV
- an object will decrease its temperature if it emits more radiation that it absorbs.
The earth’s energy balance
Incoming solar energy = 100% Absorbed by land an oceans = 51% Reflected by atmosphere = 6% Reflected by clouds = 20% Reflected from earth's surface = 4% Absorbed by atmosphere = 16% Absorbed by clouds = 3% (Radiates to space from clouds and atmosphere = 64%) (Radiates directly to space from earth = 6%) Radiation Absorbed by atmosphere = 16% Carried to clouds and atmosphere by energy in water vapour 23% Conduction and rising air 7%
How can we describe the earth’s energy balance ?
The amount of energy leaving the atmosphere is the same amount coming in
Intensity and wavelength
Intensity is the energy emitted per square metre per second, or the power emitted per square metre. The intensity and wavelength of the radiation emitted by a body depend on its temperature. As gets hotter the intensity increased and the wavelength that corresponds to the maximum intensity decreases.
What is the greenhouse effect ?
Some gases in our atmosphere naturally absorb some energy keeping the earth at a higher temperature than if there were no atmosphere. Scientists believe humans have disrupted this natural balance warming the earth due ro an increase in natural gases.
Greenhouse gas affects on the earth’s temp
Usually power from the sun absorbed and earth atmosphere radiate the same power that they recieve.
With greenhouse gases power is absorbed from the sun as usual and the earth and the atmosphere radiate less than they recieve as greenhouse gases absorb some energy increasing the temp.
Eventually the earth and the atmosphere go back to radiating the same energy they recieve but increased as the extra greenhouse gases absorb more energy. New constant temp
(WORKED EXAMPLE) explain why the temperature of the earth changes over the course of the day.
During the day the side of the earth facing the sun absorbs more than the other side so warms up. The opposite happens at night when facing away from the sun .
