Astrology and Cosmology Flashcards
Formula for Wien’s displacement law.
λmax = constant / T
Formula for radiant flux intensity.
F = L /(4πd^2)
Hubbles law formula.
v = Ho * d
Time for light to travel form earth to sun.
8 min
Explain what is meant by redshift.
The relative motion between source and observer . The wavelength apeears longer shifting the colour towards red. This is due to a receding source.
Why is line spectra used rather than continuous spectra to study redshift?
-All wavelengths are shifted so UV becomes visible light or visible light becomes infrared.
-So that shift can be measured
Define luminosity
The total power of radiation emitted by a star.
Define standard candle
An object with known luminosity.
State Wein’s displacement law.
Wavelength of a maximum intensity is inversely proportional to the thermodynamic temperature.
State Hubble’s law
The recession speed of the galaxy is directly proportional to the distance to the galaxy from the observer.
The names of 2 standard candles.
-Type 1A supernova
-Cepheid variable stars
Define radiant flux intensity
The radiant power transmitted normally through a surface per unit area, of radiation measured on defined as Earth.
State the two assumptions of radiant flux intensity.
-The power of a star is uniformly distributed in space.
-There is negligible absorption of power in space.
Define a black body
An idealised object that absorbs all incident electromagnetic radiation.
How do cosmologists determine that light from a distant star has undergone redshift?
-They examine the lines in the spectrum from the star and compare them to the known line spectrum. If the lines from the stars appear shifted it means that the light has undergone redshift.
