Week 3 Spectra, Spectral Energy Distributions & Shockwaves Part 1 Flashcards
define spectrum
plot of flux/intensity distribution as a function of frequency or wavelength
what is brightness temperature
measure intensity at one frequency and match it to the Planck function
how does radiation colour correlate to temperature
blue radiation is associated with higher temps and red radiation with lower temps
what is the colour temperature equation
T = 7200/[(B-V)+0.64]
where B-V is the colour index
define colour index
difference in magnitude between blue light and visible light
what is the Stefan-Boltzmann equation
P = σT^4
what is the Wien limit
hf»_space; kT
what is the Rayleigh-Jeans limit
hf «_space;kT
what are three requirements for a gas to be modelled as a fluid
mean free path «_space;length scales of changes in gas
meaningful small volumes are defined
volume element should contain enough particles to describe the gas in a statistical sense
what 3 conservations are important for fluid mechanics
conservation of mass
conservation of momentum
conservation of energy
what are the three equations of state in fluid mechanics that derived from the conservations
P = nkT P = Kρ^γ P = Kρ
when does a shockwave happen
generally happens when a supersonic flow of gas meets an obstacle or when an object moves supersonically through a gas
what does a shock result in
discontinuities in the thermodynamic properties
define ram pressure
momentum gets transferred between object and gas
define supersonic velocity
velocity that exceeds the speed of sound
