Temperature
• What is temperature
• Units
• Blackbody Radiation
What is temperature?
Robert Brown
Scottish
1773-1858
Botanist – named the
cell nucleus
http://upload.wikimedia.org/wikipedia/commons/4/43/Brown.robert.jpg
http://www.doc.ic.ac.uk/~nd/surprise_95/journal/vol4/ykl/report.br1
http://cnx.org/content/m14354/latest/Graphic4b.jpg
Temperature is motion
Einstein’s explanation of Brownian
motion won him a Nobel Prize
Units
• °Celsius
• °Fahrenheit
• Kelvin
Gabriel
Fahrenheit
German
1686-1736
http://centros5.pntic.mec.es/~virge133/emisora/pilares/cfk_cristina
_archivos/image004.jpg
Fahrenheit
• Wanted to set 100°F as body
temperature
• Really 98.6°F is body temperature
• 0°F is triple point of water
Anders Celsius
Swedish
1701-1744
http://www.termopares.com.br/anders_celsius/01.jpg
Celsius (Centigrade)
• 0°C is freezing point of water
• 100°C is boiling point of water
William
Thomson
Lord Kelvin
Irish
1824-1907
http://upload.wikimedia.org/wikipedia/commons/a/a0/Lord_Kelvin_photograph.jpg
Kelvin
• Same scale as Celcius
• 0K is Absolute Zero
Absolute Zero
• All motion of particles stop
• Pressure drops to 0
• Volume drops to 0
• Coldest possible
• Not actually physically possible to
reach, since will be warmed by
environment
Temperatures
Event °F °C K
Absolute Zero -460 -273.15 0
Universe -454 -276 3
Water freezes 32 0 273.15
Room temperature 65 20 293
Body Temperature 98.6 36 309
Water boils 212 100 373
Sun’s surface 10,000 5,500 5,800
Interior of Sun 18 million 10 million 10 million
Blackbody radiation
• “Blackbody” is an object that absorbs
light of all colors, and also emits light at
all colors.
• Temperature makes objects glow.
Max Planck
German
1858-1947
http://upload.wikimedia.org/wikipedia/commons/d/d7/Max_planck.jpg
Planck’s Law
• Completely describes the light
(blackbody radiation) coming from an
object.
http://abyss.uoregon.edu/~js/images/planck_curve.gif
http://upload.wikimedia.org/wikipedia/commons/thumb/a/
a2/Wiens_law.svg/300px-Wiens_law.svg.png
Jožef Stefan Ludwig Boltzmann
Slovene Austrian
1835-1893 1844- 1906
http://upload.wikimedia.org/wikipedia/en/6/60/Josefstefan.jpg
http://upload.wikimedia.org/wikipedia/commons/a/ad/Boltzmann2.jpg
Stefan-Boltzmann Law
• L=T4
• The total brightness of an object (at all
colors added together) depends on the
Temperature to the 4th power.
• Temperature makes objects glow. The
hotter it is, the more it glows.
Wilhelm Wien
German
1864-1928
http://upload.wikimedia.org/wikipedia/en/1/10/WilhelmWien1911.jpg
Wein’s Law
• max=2,900,000/T
• What color an object is brightest at
depends on the Temperature of the
object.
• Hotter objects are brightest in
blue/purple (and ultraviolet).
• Cooler objects are brightest in red (and
infrared).
http://ircamera.as.arizona.edu/NatSci102/images/sep25001.gif
http://hypertextbook.com/physics/modern/planck/
http://www.oswego.edu/~kanbur/a100/images/planck.jpg
Next Time
• What is light?
• What is color?
• More ways of creating light