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.