LECTURE 4
What type of radiation does the Earth primarily emit? The sun?
Earth's surface and the sun absorb and emit radiation at many wavelengths
If an object emits and absorbs the same amount of radiation, temperature remains the same, and this is called...
Radioactive Equilibrium Temperature
Why does the temperature usually drop at night?
The earth emits more energy than it receives, so its temperature DECREASES
The Greenhouse effect
The greenhouse gases only absorb IR radiation and throw it in all different directions, some of it goes into space, other parts of it is put it in the earth, that's why the earth has become warmer
What objects emit radiation?
all objects emit radiation at all times
Green objects absorb...
all wavelengths except green- which is reflected
What is a greenhouse gas?
gases that only absorb/emit radiation at certain wavelengths
Darker objects absorb...
many colors trees, asphalt, dark roofs, black cars WARM QUICKLY IN THE SUN
Albedo
measure of reflectivity equation: reflected radiation divided by total incoming radiation
Is the atmosphere a blackbody?
No
What controls the intensity and amount of radiation an object emits?
Objects with HIGHER temperatures emit SHORTER (MORE ENERGETIC) wavelengths
Lighter colors...
REFLECT more colors. Snow, white pavement, light sand TEND TO NOT WARM FAST IN THE SUN
Blackbodies
Any object that is a perfect absorber as it is emitter
Why are sunsets red?
As the sun is lower, the air molecules have to pass through more of the atmosphere and the blue scatters away, then all we see is the red light
Why is the "greenhouse effect" a poorly named phenomenon?
Atmosphere doesn't trap the heat like a greenhouse, it just re-emits the heat in different directions, so that's why the name is not accurate
Examples of Greenhouse gases
Carbon dioxide H2O
Why are the clouds white?
Clouds reflect all colors of light equally as well Our eyes detect a mixture of all colors of light as WHITE
Why is the sky blue?
During the day, air molecules scatter blue light four times more than red light, we perceive it as blue
Why do you feel hotter in the sun?
Your body (or earth) receives more energy than it emits, so its temperature INCREASES
Objects that are hot enough emit __________.
visible light ex: red hot, white objects. The sun.