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# MCAT Physics Ch. 9

Term | Definition |
---|---|

Photoelectric Effect | Ejection of an electron from the surface of a metal in response to light |

Threshold Frequency | Minimum light frequency necessary to eject an electron from a given metal |

Work Function Is The: | Minimum energy needed to eject an electron from a given metal. This value depends on the metal used. |

The Greater The Energy Of The Incident Photon Above The Work Function, The: | More kinetic energy the ejected electron can possess |

The Ejected Electrons Create A: | Current, the magnitude of which is proportional to the intensity of the incident beam of light |

Bohr Model Of The Atom | States that electron energy levels are stable and discrete, corresponding to specific orbits |

An Electron Can Jump From A Lower-Energy To A Higher-Energy Orbit By: | Absorbing a photon of light of the same frequency as the energy difference between the orbits |

When An Electron Falls From A Higher-Energy To A Lower-Energy Orbit, It: | Emits a photon of light of the same frequency as the energy difference between the orbits |

Absorption Spectra May Be Impacted By: | Small changes in molecular structure |

Fluorescence Occurs When: | A species absorbs high-frequency light and then returns to its ground state in multiple steps. Each step has less energy than the absorbed light and is within the visible range of the electromagnetic spectrum. |

Nuclear Binding Energy | Amount of energy that is released when nucleons (protons and neutrons) bind together. |

The More Binding Energy Per Nucleon Released: | The more stable the nucleus |

The Four Fundamental Forces Of Nature Are: | The strong and weak nuclear force (2), which contribute to the stability of the nucleus. Also, electrostatic forces and gravitation. |

Mass Defect | Difference between the mass of unbound nucleons and the mass of the bound nucleons within the nucleus. |

Unbound Constituents Have: | More energy and have more mass than the bound constituents |

Mass Defect Is The Amount Of: | Mass converted to energy during nuclear fusion |

Fusion Occurs When: | Small nuclei combine into larger nuclei |

Fission Occurs When: | A large nucleus splits into smaller nuclei |

Radioactive Decay | Loss of small particles from the nucleus |

Alpha Decay | Emission of alpha particle (alpha, 4/2 alpha, 4/2 He) which is a helium nucleus |

Beta-negative Decay | Decay of neutron into a proton, with emission of an electron (e-, B-) and an antineutrino (Vunderscore) |

Beta-Positive Decay (Positron Emission) | Decay of a proton into a neutron with emission of a positron (e+, B+) and a neutrino (V) |

Gamma Decay | Emission of a gamma ray which converts a high-energy nucleus into a more stable nucleus |

Electron Capture | Absorption of an electron from the inner shell that combines with a proton in the nucleus to form a neutron |

Half-life | The amount of time required for half of a sample of radioactive nuclei to decay |

Exponential Decay | The rate at which radioactive nuclei decay is proportional to the number of nuclei that remain |

Eq. 9.1: Energy Of A Photon Of Light | E = h*f. h = Planck's constant (6.626 x 10^-34 J*s). f = frequency of the light. |

Eq. 9.2: Maximum Kinetic Energy Of An Electron In The Photoelectric Effect | Kmax = h*f - W. h = Planck's constant (6.626 x 10^-34 J*s). f = frequency of the light. W = work function of the metal in question. |

Eq. 9.3: Work Function | W = h*fT. h = Planck's constant (6.626 x 10^-34 J*s). fT = threshold frequency. |

Eq. 9.4: Mass Defect And Energy | E = mc^2. E = energy. m = mass. c = speed of light (3.00 x 10^8 m/s). |

Eq. 9.5: Nuclear Decay (General Form) | A/Z X --> A^1/Z^1Y + emitted decay particle. X = parent nuclei. Y = daughter nuclei. |

Eq. 9.6: Alpha Decay | A/Z X --> A-4/Z-2 Y + 4/2 alpha. alpha = 4/2 He nucleus. |

Eq. 9.7: Beta-Negative Decay | A/Z X --> A / Z+1 Y + B-. B- = neutron (Z = -1, A = 0) |

Eq. 9.8: Beta-Positive Decay (Positron Emission) | A/Z X --> A / Z-1 Y + B+. B+ = neutron (Z = +1, A = 0) |

Eq. 9.9: Gamma Decay | A/Z X*(asterisk) --> A/Z X + Y. Y = Gamma, which are high energy, high frequency protons. |

Eq. 9.10: Electron Capture | A/Z X + e- --> A/Z-1 Y. Y = Gamma, which are high energy, high frequency protons. |

Eq. 9.11: Rate Of Nuclear Decay | Delta n / Delta t = - lambda * n. n = number of nuclei that remain. |

Eq. 9.12: Exponential Decay | n = n0*e^-lambda*t. n0 = number of undecayed nuclei at time t = 0. |

Eq. 9.13: Decay Constant | lambda = ln*2 / T 1/2 = 0.693 / T 1/2. |