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# EK Physics 6

### waves

Question | Answer |
---|---|

wave | transfer of momentum & energy from 1 pt to another |

three types of waves | mechanical, electromagnetic, and matter |

mechanical waves | obey laws of classical physics and require medium to travel, separated into transverse and longitudinal waves |

transverse wave | one which medium is displaced perpendicularly to the direction of wave propagation |

longitudinal wave | one which medium is displaced parallel to the direction of wave propagation, ex: sound wave |

wavelength | x-axis displacement of wave, from any point to the next point it repeats itself |

frequency | # of wavelengths that pass thru fixed point in one second, measured in Hz |

velocity relates to frequency and wavelength by which eqn? | v = f*wavelength |

period | reciprocal of frequency = the number of seconds required for 1 wavelength to pass thru a fixed point |

amplitude | A, maximum displacement from zero, always positive |

transverse and longitudinal waves represented mathmetically with.. | sine functions |

for a gas, velocity increases or decreases with temperature | increases - the greater th temperature, the greater the random velocity and the greater the sound wave velocity |

two aspects of medium affect velocity | 1. medium's resistence to change in shape or elasticity and 2. the medium's resistance to change in motion or inertia |

do sound waves move more quickly through hot or cold gases? | hot gases - velocity is limited by the average speed of molecules within that gas |

wave intensity increases with... | the square of the amplitude and square of frequency for all waves |

power of wave | rate at which wave transfers energy, expressed in intensity |

intensity level | (B) = 10log(I/Io) given in dB's |

phase of a wave | relates to its wavelength, freq, and place and time of origin = kx-omega*t ** horizontal shift of a wave on a graph |

constructive interference | occurs when the sum of the displacements results in a greater displacement |

destructive interference | occurs when the sum of the displacements results in a smaller displacement |

beat | occurs when 2 waves with slightly different f are superimposed where at some points will have constructive/destructive interference -*alternating increase and decrease in the intensity of noise |

beat frequency eqn | fbeat = f1 - f2 |

pitch | what is actually heard from the beat, average of the frequencies of the two frequencies, high notes - high pitch, and high frequency |

when a wave transfers from one medium to the next, the wavelength ____ and the frequency ____. | wavelength changes and frequency remains the same |

node | point in wave with zero displacement |

antinode | point of maximum constructive interference |

standing wave | condition where string holds perfectly still at nodes and moves violently up and down at the antinodes |

first harmonic | aka fundamental wavelength, longest wavelength and created w/ the fewest # of nodes - two |

second harmonic | one more node than the first harmonic |

harmonic series where each end is tied down as a node or both ends are antinode | L = n*wavelength/2 where n (=1,2,3..) is the number of harmonic and L is the distance btw the two ends of the strong |

harmonic series for string tied only at one end | L = n*wavelength/4 (n =1,3,5..) |

resonant frequency | natural frequency |

period for mass on a spring | T = 2*pi*sqrt(m/k) |

period for pendulum | T = 2*pi*sqrt(L/g) |

doppler effect | if source moves relative to receiver of the waves, each wave will travel a diff distance in order to reach the observer so it won't reach observer at the same frequency |

when relative velocity brings source and observer closer... | observed frequency goes up and observed wavelength goes down |

when the relative velocity brings source and observer further away | observed frequency goes down and observed wavelength goes up |

doppler effect eqn | change in f / source f = v / c = change wavelength / source wavelength where v = velocity of source and c = velocity of wave |

wave intensity is proportional to... | its energy |