From the universe to the atom Flashcards
(34 cards)
who discovered that the universe expanded
Edwini Hubble
What is hubble’s law
Huble found that the “speed of reccesion” is actually proportional to the distance away. it is expressed as V = H(o) d
v is the speed of recessions (kms^-1)
Ho is Hubble’s constant (Kms^-1 Mpc^-1)
d is the distance away (Mpc)
What is the Steady State theory
infinite - the “outer” stars would never reach infinity and so could go on moving away from us forever
expanding - matter is being created all the time at just the right rate to keep the density of the universe constant
Who made the steady state theory
Fred Hoyle
what is inflation Big Bang theory
Inflation is the period at the begining of the Big Bang. It lasted for about 10^-24 s but during that time the size of the universe had expanded to about 10^50 times its original size. It was necessary to prevent a very rapid collapse of the universe back into a black hole.
For every matter particle what comes with it
antimatter particles
What is pair production
it is the production of two opposite particles.
What happened to the particles after the inflation
particles and anti particles annihilated each other to produce high-enery gamma photons (electromagnetic radiation) with those particles colliding with others to form new particle gains. As the universe cooled down, there was a huge reduction the total amount of matter.
What was the first elementary particle
Quarks, which then combined to form prototns and neutrons.
What were the first three elements that formed in the universe
hydrogen, helium and lithium.
How did life come to exist if all the matter and antimatter anhilated each other?
there was actualy a slight imbalance between anti matter and matter and the imbalance of the matter left over makes up the universe today.
what is the process of nuclear fusion that results in the formation of nuclei of heavier elements
Nucleosynthesis
Where could the CNO cycle be more dominant in the main sequence
in more massive stars
where would the proton-proton chain most likely occur in the main sequence
in the shorter stars
where would the Helium fusion most likely occur
in massive stars outside the main sequence
Who made the first model of the atom
Joseph John Thomson
what was Thomson’s experiment using cathode rays
Thomson used cathode ray tubes to study electric disharges.
He found that the tube glowed more when the gas was at a lower pressure which showed that something was exciting the gas. When the tube was painted with phosphorescent paint, the paint opposite the negatively charged cathde sparked and glowed.
Thomson then placed two electrically chaged plates above and below the cahtode ray tube and discovered that the ray was deflected to the positive plate indicating that the beam was negatively charged.
what are cathode rays
they are streams of electrons observed in vacuume tubes.
What was Thomson’s charge to mass ratio experiment
Thomsoon performed his experiment to measure the mass of the paritcle by first using an electric and a magnetic field force to balance the electrons. This enabled Thomson to calculate the speed of the electrons and then he turned off the magnetic field to which the beam was defelected under the influence of the the electric field alone.
Through the deflection of the beam measured, Thomson found the charge-to-mass ratio.
Who conducted the Oil-Drop experiement
Robert Millikan
What was the Oil-Drop experiment
It was an experiment used to measure the charge on the electron.
Millikan used a spray of oild drops between two metal plates. An electrical potential was applied between the plates as the charged drops became suspended between them. In order to do this the drop must have been in equillibrium the magnitude of the upward force balanced (electrostaic force experinced by the charge in the electrical field) the downward force (gravtiy).
Millikan discovered that the charge on a drop was always a multiple of 1.6 x 10^-19 C which is 1% off from the modern value of the charge.
What was Thomson’s model
It was the Plum Pudding model.
What is the Plum Pudding model
It consited of a disfuse ball of postivie charge with negatively charged particles floating within.
What was the golden foil experiment
it was an experiment performed by Geiger to explore the idea of looking for alpha particles scattered at large angles.
He had a golden foil surrounded by a detecting screen with an aplha particle emitter emitting alpha paticles through a slit.
It was first theorised that the particles were supposed to go through the entire model but what actually happened was that it deflected around the center of the atom.
They discovered that the electrons had dispersed when passing through the golden foil and deflected at many different angles, and some of them were greater than 90 degrees.
