Chapter 5.4 and 5.5 Flashcards
Thermal Equilibrium
When heating is balanced by cooling.
Temperature
A measure of how energetically the atoms that make up an object are moving about.
Thermal Motions
The random motion of atoms and molecules that create temperature.
Absolute Zero
The temperature at which all thermal motions stop.
Kelvin Temperature Scale.
Starts with absolute 0 at 0. Same degrees at Celsius add 273.15. So water freezes at 27.15 and boils at 373.15K
Why is Kelvin useful?
When temperature is measured in kelvin, the energy of the particles is proportional to the measured temperature. So, 200k is twice as energetic as 100k.
Luminosity
The total amount of light leaving a source. Measured in watts.
Luminosity
The total amount of light leaving a source. Measured in watts.
Blackbodies
Objects that emit electromagnetic radiation only because of their temperature, not their composition. Emit just as much radiation as their absorb through their surroundings
Blackbody Spectra
The spectrum of electromagnetic energy emitted by a blackbody per unit of area per second.
Stean Boltzmann Law
The increase of the luminosity of a blackbody is proportional to the fourth power of the temperature. F=ot^5
Flux
Amount of energy radiated by each square meter of the surface of an object each second.
Luminosity= (flux) * _____
Surface area of the object.
F=oT^4
Stefan Bolzman law. Flux is equal to sigma times the temperature to the fourth power.
If the temperature of an object doubles what happens to the amount of energy being released?
It goes up by 2^4 or 16 times the original energy.
Wien’s Law
The wavelength of the spectrum is inversely related to th temperature of the object. If you double the temperature, the peak wavelength becomes half of what it was. T= b/peak wavelength
Stefan Boltzmann Constant
5.67 times 10^08 watts/m2k^4
Brightness
The amount of light arriving at a particular location.
Brightness vs Luminsoity
Brightness depends on distance because it measure slight arriving at a location. Luminosity is independent because it measures light leaving an object.
How does brightness depend of distance.
Is is inversely proportional to the square of the distance between the source and the object.
Brightness=
Luminsoity/4pied^d2
Albedo
Fraction of light that reflects from a planets surface
A planet covered in snow would have close to a ___ albedo. A planed covered in black rocks would have close to ___ albedo
1, 0
