Doppler Effect, Red Shift and The Big Bang Theory Flashcards
What is the doppler effect?
The change in frequency and wavelength when sound moves towards/away from you.
Why does the doppler effect occur?
Because the sound waves bunch together when moving towards you and spread out as they move away from you.
What is red shift?
When a light source moves away from us and appears to shift towards the red end of the electromagnetic spectrum.
What is blue shift?
Same as red shift but for objects moving towards us.
What colour is the lowest frequency of light?
Red.
How can you work out red shift using absorption lines?
By measuring the difference between the absorption lines of the emitted spectrum and the red-shifted spectrum and using the equation.
State the cosmological principle.
On a large scale the universe is:
- homogeneous (every part is the same as every other part)
- isotropic (everything looks the same in every direction) so it doesn’t have a centre
What is Hubble’s Law?
Hubble’s Law states that the recessional velocity of a galaxy is proportional to it’s distance from us.
State the big bang theory.
The universe started off very hot and very dense (perhaps as an infinitely hot, infinitely dense point) and has been expanding ever since.
What is a good way to visualise the Universe?
As the surface of a balloon with lots of dots in it - as you blow it up, all the dots move away from each other, but no one dot is at the centre of the expansion.
What is the equation for the age of the Universe?
t = distance/velocity
= 1/H
What is dark energy?
A mysterious source which is accelerating the expansion of the Universe.
What is Cosmic Microwave Background Radiation?
The EM radiation which was produced during the Big Bang, observed today in the microwave region due to it being stretched from the Universe expanding.
What are the two main things which provide evidence for the Big Bang Theory?
CMBR and relative abundance of H and He.
