Section 13 - Turning points Flashcards
What where michelson and morely trying to do with the interferometer?
They tried to measure the absolute speed of the earth through the ‘ether’
What did michelson and morely expect to happen in the experiment?
the motion of earth to effect the speed of light they measured in certain directions.
Describe the setup of the michelson and morely experiment
two mirrors and a partial reflector made of semi silvered glass block + glass block
What does the glass block do in the michelson and morely experiment?
1) ensures that both beams of light travel through the same amount of air and glass
Explain the processes in the michel and morely experiment ( 6 PONTS )
1) Monochromatic light is sent to the partial reflector
2) The light is then split into two beams at right angles to eachother
3) the beams are then reflected into M1 and M2
4) The waves meet back at the partial reflector and form an interference pattern
5) interference pattern is recorded
6) interferometer rotated through 90 degrees and repeated
What was the expected outcome for the michelson and morely experiment?
they expected that the light moving parallel to the motion of the earth should take longer to travel to the mirror and back, compared to travelling at right angles
so rotating the apparatus should’ve changed the travel times for the two beams, which would cause a shift in the interference pattern.
So what was the end result of the michelson and morely experiment?
No change in interference pattern ….
therefore,
1) ether doesn’t exist
2) speed of light is the same value for all observers
State Einstein’s postulates
1) The speed of light is invariant ( in a vacuum ) - therefore independent of the speed of the observer
2) Physics laws have the same form in all inertial frames - so outcomes when in an intertial frame wont change
What is the half life of a muon in a lab
2 microseconds
Describe how you’d measure muon decay
1) measure speed v, of muons
2) place a detector at a high altitude to measure count rate
3) place detector at ground level
4) compare the two figures
Why could we in practice have an infinite kinetic energy but not a speed equal to the speed of light?
mass would tend to infinity as c -> infinity
so ek could tend to infinity
ek only accepts smaller values of speed
because e = mc^2 implies the mass is infinite, thus the energy
explain how bertozzi demonstrated that mass increased with speed ( 5 POINTS )
1) he used linear particle accelerators to accelerate pulses of electrons to a range of energies, they were smashed into an aluminum disc
2) he measured time taken by electrons to reach disc
3) unexpectedly, as energy of electrons increased, speed didnt increase but tended towards 3x10^8
4) he used the heat generated by the collisions to find kinetic energy of particles before impact
5) he plotted this, and it was similiar to einsteins formula
