(3) geo: electromagnetic radiation and the sun
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32 Terms
energy
the ability to do work or change the state of matter
where does the earth gets its energy?
from the sun
electromagnetic radiation
energy that moves through space by vibrating electrons
frequency
the number in waves that passes a fixed point in a given time
wavelength
the distance between two peaks
amplitude
the height of a peak or trough
electromagnetic spectrum
the range of wavelengths of electromagnetic radiation
what emits radiation?
everything, we use black bodies to understand how
wein’s law
the type of radiation matter emitted is proportional to the temperature of the object
hotter objects = bluer light, cooler objects = redder light
wein’s law
stefan-boltzmann law
as an object gets hotter, it emits more energy
since the sun is hotter..
it emits more energy at a shorter wavelength (about 72 mill watts m^-2 of shortwave EMR)
since the earth is cooler…
it will emit less energy at a longer wavelength (about 240 watts m^-2 longwave EMR)
insolation
the amount of energy coming into the earth from the sun
how much energy comes from the earth?
it varies by latitude and season
earth’s energy balance: input
shortwave radiation, sun to earth
ultraviolet, visible, shortwave infrared
earth’s energy balance: output
longwave radiation, earth to space
thermal infrared
net radiation in the top of the atmosphere
positive in the low latitudes, negative in the high latitudes
what are the celestial motions of the earth?
revolution and rotation
revolution
earth revolves around the sun once every 365.25 days
rotation
earth rotates along an axis once every 24 hours
cause of seasons
axial tilt = 23.5 degrees
what if there is no tilt?
no tilt = no seasons
90 degree tilt?
extreme seasons
concentrated sunlight
more energy
diffuse sunlight
less energy
june 22nd
sun is directly overhead the northern hemisphere (more direct radiation to north) (summer solstice)
december 22nd
sun is directly overhead the southern hemisphere (more direct radiation to south) (winter solstice)
solstice
the extremes in the sun’s movement in the sky
equinox
earth experiencing 12 hours of day length across all latitudes when the sun is directly overhead the equator (september 23rd and march 21st)
which day is the longest in the NH and the shortest in the SH
june 22nd
which day is the longest in the SH and the shortest in the NH?
december 22nd