Stars as Black Bodies Flashcards
What is a black body?
A body that absorbs all EM radiation of all wavelengths and can emit all wavelengths of EM radiation
What can stars be approximated to?
As black bodies
What is a black body radiator?
A perfect emitter and absorber of all possible wavelengths of radiation.
What does Wien’s law show?
as the black body gets hotter, the peak wavelength decreases, the frequency increases and the energy of the wave increases.
What is Wien’s law used for?
To estimate the temperature of black-body sources.
What does the intensity of light emitted by a star follow?
the inverse square law, meaning intensity is inversely proportional to the distance between the star and the observer.
What is Stefan’s law?
The power output of a star is the total power of the star’s surface temperature and is directly proportional to the surface area.
From Earth, we can measure the intensity of a star. What is the intensity of a star?
the power of radiation per square metre, so as the radiation spreads out and becomes diluted, the intensity decreases.
what do need to assume to use the inverse square law?
you need to assume that the star is spherical, and it gives you out an even amount of power in every direction
How do you use all the 3 laws to work out all sorts of things about stars?
you assume that stars behave as black bodies.
What objects emit EM radiation?
All objects that are hotter than absolute zero emit EM radiation due to their temperature.
