2.5 Quantum Physics Flashcards
Define a photon
Indivisible packet of electromagnetic energy
Equation for calculating energy in a photon
E = hf
Equation for energy in a photon involving wave equation
E = hc/&
Use the photon model to explain the photoelectric effect (2 key words)
Photon strikes an electron on a certain energy level. If the energy of the photon is greater than the work function of the metal the electron is freed
Equation to find ke of photon ejected
0.5 m v^2 = hf - hf0
Equation to find change in energy of photon
hf = deltaE
What is the lowest energy level in an atom called
Ground state
What is ground state
Lowest possible energy level in an atom
What is the term given to an electron that has jumped up an energy level ? Gone down an energy level?
Excitation
De excitation/relaxation
Explain laser action (3 key terms) (4)
e are excited to metastable state where they stay for longer time
Population inversion because more e are in excited state compared to lower ( ground ) state
Stimulated emission when e fall
Photon emitted has same energy as the difference between 2 energy levels
How are X rays produced
Rapid deceleration of electrons emits photons of X rays
Stimulated emission produces photons of X rays
State similarities and differences between CT scans and X rays
Sim: both produce image using x rays
Diff: in CT scans, the x ray tube and detector move in phase. In x rays machines are all stationary
CT allows for organs to be viewed, X rays are just for bones
What does CT stand for
Computed tomography
Disadvantages of X-rays and CT scans
Radiation dosages can be harmful (especially to pregnant women and children)
CT is more expensive
Describe how X-rays are produced ( machine)
High speed e are produced when thermionic emission of a filament happens. They’re accelerated by the pd across filament
e are beamed towards copper anode with tungsten target where they’re rapidly decelerated, producing x rays
How is an X-ray tube insulated
Lead shield
Aluminium filter (for lower energy X-rays)
Roughly How much energy is lost in the production of X-rays and how is this energy taken care of?
Over 99%
Coolant is circulated through copper block
How do you increase the number of X-rays produced
How do you increase penetrating power of X-rays produced
Increase current through filament
Increase pd across filament
First 5 + infinity energy levels for hydrogen
And approx spacing
-13.59
-3.4
-1.51
-0.85
-0.54
0
Top 4,5 and infinity close then spacing gets bigger between levels
What is an electron volt and what does 1eV = in joules
1 eV is 1 electron accelerated across a pd of 1V
1.6 x 10^-19 J
To convert joules to eV what do you do?
Divide by 1.6x10^-19
For emission of an e from a metal surface, what must the f be and how soon will it happen
f >f0 (threshold f)
Instantly
State 2 conditions required for an e to be emitted from the surface of a metal
Photon needs to hit e
Energy of photon > work function of metal / f>f0
What is the mass of an electron (kg)
9.11x 10^-31
Electron volt
Energy possessed by an electron which has been accelerated across a pd of 1V
Collimated
All parts travel in same direction
Metastable state
Energy level which e is stable for several magnitudes of time longer than a normal energy level
