1. Bellwork 3/2
Describe how pressure & temperature change in our atmosphere.
What kinds of gases/materials are in our atmosphere?
Do the amounts of gases in the atmosphere matter? Use examples from your homework to explain.

2. Really quick, about the Safety Drill

3. Fate of Incoming Radiation
Radiation- emission of energy in the form of an electromagnetic wave
…for this class…the radiation we most care about is energy coming from the sun
 which travels in the form of a wave

4. 4 Laws Governing Radiation:
All objects emit radiant energy
2. Hotter objects radiate more total energy per unit area than cooler objects

5. 4 Laws Governing Radiation
The hotter a radiating object, the shorter the wavelength
4. Objects that are good absorbers of radiation, are good emitters as well

6. Which is emitting more energy, the fire or the coffee?

7. Which is emitting longer wavelengths, the fire or the coffee?

8. Which of these are emitting radiation?

9. Fate of Incoming Solar Radiation
There are 3 things that can happen to waves of energy traveling through our atmosphere:
Reflection
Scattering
Absorption
**The “fate” of the radiation depends on how the wave interacts with particles in our atmospehre

10. REMEMBER: Our atmosphere is made up of lots of gases and particles
Major components
Nitrogen, Oxygen, Argon
Variable Components
Water vapor, aerosols, ozone
Radiation (energy waves) interact with each of these gases and particles in different ways

11. Setting the Scene… The sun is OUTSIDE of our atmosphere
There are gasses and particles INSIDE our atmosphere
We’re talking about what happens when the two meet

12. Reflection:
light bounces off of a surface at the same angle at which it hits the surface AND with the same intensity
about 30% of solar energy reaching Earth is reflected back to space
HOW??
--Bouncing off of those gases & particles that make up our atmosphere 

13. Scattering
light bounces off a surface, but creates a larger number of weaker waves AND…
rays travel in all different directions

15. Absorption Gases are selective absorbers
absorb strongly in certain wavelengths
When radiation is absorbed, energy is transformed into molecular motion
which causes a rise in temperature

17. How does this play a role in creating different colors in the sky?
An application of scattering!

18. Some gases are better at scattering than others…
Nitrogen and Oxygen are very good at scattering high energy (low wavelength) waves

19. This leads to BLUE SKIES!
Most of the energy (in the visible light spectrum) being scattered is Blue, Indigo & Violet
Our eyes aren’t very sensitive to Indigo & Violet, se we see the daytime sky as blue

20. This also leads to RED SUNSETS!
As the sun approaches the horizon, the radiation must travel through more atmosphere
As the radiation path length increases, the wave encounters more atmospheric particles…meaning blue light is all scattered away and red/orange light reaches our eyes

21. “Blue Skies & Red Sunsets”