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MODULE 3.1
Earth’s Energy Budget
Energy from the Sun and Earth
Lesson Goal:
» Contrast the amount and type of energy emitted by objects at different temperatures, in particular, the Sun versus Earth.
Energy from the Sun and Earth
What can we actually measure?
Taking the Sun’s temperature
T?
Reading Review
THE ELECTROMAGNETIC SPECTRUM
Gamma Ray X-Ray Ultraviolet Visible Infrared Microwave Radio
MO
DIF
IED
FRO
M H
TTP:
//M
YN
ASA
DAT
A.L
ARC
.NA
SA.G
OV/
IMA
GES
/EM
_SPE
CTR
UM
3-N
EW.JP
G
Which of these stoves is the hottest?
A B C
Which of these stoves is emitting radiation with the LONGEST peak wavelength?
A B C
They are all emitting at the same peak wavelength
D
Which of these stars is the hottest?
A B C
IMA
GE
CRE
DIT
S: N
ASA
Where are the peak wavelengths for the different stars?
THE ELECTROMAGNETIC SPECTRUM
Gamma Ray X-Ray Ultraviolet Visible Infrared Microwave Radio
MO
DIF
IED
FRO
M H
TTP:
//M
YN
ASA
DAT
A.L
ARC
.NA
SA.G
OV/
IMA
GES
/EM
_SPE
CTR
UM
3-N
EW.JP
G
Emission Spectra for Sun and EarthIM
AG
ES: N
ASA
Radi
atio
n In
tens
ity SUN
EARTH
0.1 1 10 100Wavelength, �(microns)
Infrared VIS UV
… Wien s law … Tsun = 5800 K ~0.5 +m
)&% )$%
Earth emits radiation with a peak wavelength of about 11.4 microns (µm).
A. ! 3.9 KelvinB. !15 KelvinC. ! 255 KelvinD. !273 KelvinE. 305 Kelvin
IMA
GE:
NA
SA
Using Wien’s Law, what’s Earth’s temperature?
Ȝm = 2897 / T
CHOOSE THE CLOSEST ANSWER.
Stefan-Boltzmann’s law (very useful!)
����������������� F is the energy emitted, per unit time, per unit area, expressed in W/m2 [J/s*m2]
is a constant [5.67*10-8 W/m2K4]
T is the absolute temperature (K)
64 million W/m2240 W/m2
IMA
GES
: NA
SA
Key Points
» The Sun gives off shortwave radiation with a peak wavelength in the visible part of the electromagnetic spectrum.
» The Earth gives off long wave radiation with a peak wavelength in the infrared part of the electromagnetic spectrum.
» The general relationships are that xHOTTER objects emit MORE radiation than cooler objects, and xHOTTER objects emit radiation at SHORTER wavelengths than cooler objects
» COMING UP: These differences between radiation from the Sun and radiation from Earth are crucial to understanding the greenhouse effect.