14.5 Doppler Effect + Hubble Constant Flashcards
What is the Doppler Effect?
The change in frequency and wavelength because of velocity of source relative to observer.
How do stars emit a continuous spectrum?
Under high pressure atoms in the atmosphere emit a continuous spectrum of EM radiation.
How do stars emit an emission spectrum?
Atoms in the atmosphere at low pressure selectively absorb photons of certain wavelengths that makes their electrons excited, when they drop back photons are emitted in the emission spectrum. These are the dark lines in the continous spectrum.
How is the emission spectrum shown on the continuous spectrum?
As dark lines
What is the mixed continuous and emission spectrum called?
absorption spectrum.
What do we receive when a light source is moving away?
A light in the red end of the absorption spectrum
What end of the spectrum would be light of a light source moving towards us?
Blue
What does red shift mean for frequency + wavelength.
Increase in wavelength and decrease in frequency.
What does blue shift mean for frequency + wavelength.
Decrease in wavelength and increase in frequency.
Equation for red shift.
z = change in wavelength/wavelength
Equation for red shift in terms of frequency?
z = change in frequency/frequency
Equation for red shift in terms of hubble constant?
z = Ho/c
Equation for red shift in terms of velocity?
z = v/c
What would a negative z mean?
Blueshift, object moving towards us
What would a positive z mean?
Redshift, object moving away from us
Why do further galaxies show more redshift?
As the universe is expanding.
What did redshift tells us about the universe?
it is expanding
What is the Hubble Constant?
2.3x10^-18 s^-1
How to find the age of the universe using the hubble constant?
1/Ho
Equation for hubble constant?
v = Ho x d
What does the hubble constant support?
The big bang
What is the big bang?
The theory that the universe started off very hot and very dense and has been expanding ever since.
What is the gradient of v/d graph?
the hubble constant
What is the cosmological redshift?
Stretching of light waves due to expansion of the universe.
