2546777
Description
Flashcards by Husein Essaji, updated more than 1 year ago
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Created by Husein Essaji
over 9 years ago
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| Question | Answer |
| Explain pair production | Photon interacts with atom Energy of photon used to create particle antiparticle pair |
| What roles do exchange particles play in interactions | Transfer... Energy, momentum, force and sometimes charge |
| Electron Volt | The kinetic energy gained by an electron when it is accelerated through a potential difference of 1 volt |
| Ohmic conductor | V is directly proportional to I or Constant resistance |
| Principle property of superconductor | A material which has zero resistance |
| Definition of an excited atom | Orbital electron is at higher energy level than ground state |
| Difference between a Hadron and Lepton | Leptons don't experience strong interaction Hadrons are not fundamental particles |
| What happens to positron produced by pair production | Encounters another electron They annihilate Two high energy photons released |
| What is meant by Root mean square voltage | The equivalent dc voltage that produces the same heating effect |
| Why does current of a lamp decrease after initial increase | Resistance of filament increases because temperature of filament increases so current decreases |
| What happens to excess energy of photon in pair production | Turns into kinetic energy of photon |
| Why are different energies of photons possible when electron de-excites | The electron returns to lower energy level by a different route |
| Range of Strong Nuclear Force | Attractive 3-4 femtometres Repulsive within 0.5 fm (femtometres = ^ -15 metres) |
| Define a Hadron | Any particle or antiparticle that can interact though the strong interaction |
| Define emf | Electrical energy per unit charge produced |
| When is max power delivered to load | Load resistance = Source resistane |
| Work Function | The work function of a metal is the minimum kinetic energy needed by an electron to escape the surface of a metal |
| Internal Resistance of battery | The resistance of the material within the battery |
| Electron Capture | Orbital electron interacts with proton in the nucleus via weak interaction to form a neutron and electron nuetrino |
| Explain why kinetic energy of emitted electron has a max value | Electrons energy comes from absorption of photon. Energy required for electron varies as surface electrons require less energy. These electrons have max energy. |
| Explain why below a certain value electrons are not emitted | Work function is the min energy needed to release an electron. Below a certain frequency, energy of photon is less than work function. |
| Why is the fact that there is no time delay is important | Shows light must travel as photons which transfer energy in discrete packets |
| Explain the threshold frequency | Threshold frequency is the min frequency for emission of electron. If below this value no emission even if intensity increased because the energy of photon is less than the work function. |
| Explain why an electron moves from ground state to n=2 in excitation | Electron absorbs energy from incident electron. This ____ exact value is needed to make the transition |
| Why are electrons release from the metal surface | Light consists of photons of energy hf. An electron at the surface of metal can only gain the energy of a single photon when it interacts with one. The work function of a metal is...Therefore elctron escapes metal if hf is greater than work function. |
| Why is it important to test by experiment a scientific theory | If a reliable experiment does not support a hypothesis then the hypothesis must be changed |
| Internal resistance of a battery | The resistance of the material within a battery |
| What is the terminal voltage | Voltage across the circuit |
| Explain why emitted electrons have a range of KE | Energy is required to leave surface of metal. Max KE is hf - work function. The deeper the electrons the more energy is used to get to the surface |
| Ground state | When electrons in their lowest energy state/ most stable state |
| Excitation vs. Ionisation | Both require the right amount of energy Excitation promotes electron to higher energy level Ionisation - electron receives enough energy to leave the atom |
| Why do photons of certain frequencies cause excitation in particular atom | Electrons occupy discrete energy levels Need to absorb exact amount of energy to move to higher energy level Photons need to be of certain frequency All energy of photon is absorbed in 1 to 1 interaction |
| Explain what must happen in order for a new scientific theory to replace old one | Theory makes prediction tested by other scientists |
| Measuring voltage using osciliscope | Connect power supply to the input of the oscilloscope Time base switched off Adjust y gain until complete vertical line seen and measure. Convert by calibration. |
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