# AP Physics 2: 1.4 Probability and Systems

AP Physics 2: 1.4 Probability and Systems. Which of the following is the correct value?

 AP Physics 2 Probability and Systems Language English Language Science Practice 1 Using representations and models

### Transcript

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me or accelerating an electron through a potential difference in

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a diffraction experiment they determined that the debra lee wavelength

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of the electron is sixty six point three pico meters

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austin powers international man of mystery let's Find the value

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of that potential difference in orderto foil their evil plan

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and save the world Which of the following is the

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correct value And here are your options Right Right there

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Okay well we're not sure how one accelerating electrons health

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doctor It'll conquered the globe But then again we didn't

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go to six years in evil medical school So what

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do we know Well we do actually know something about

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too early wave lengths to really help prove that all

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that franz show the properties of waves as well as

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the properties of particles He came up with a formula

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stating that the wavelength of an electron equals planks constant

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Divided by the electrons momenta And we know that momentum

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equals mass times velocity so we can rewrite the equation

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accordingly When we hear the phrase and electrons accelerated through

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a potential difference we think Huh But we should be

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thinking of electron volts One electron volt equals the amount

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of kinetic energy gain by a single electron wanted accelerate

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through an electric potential difference of one full A single

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electron volt equals one point six times ten to the

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negative nineteen Jules do the conservation of energy You know

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that the kinetic energy of the electron equals the potential

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difference required to accelerate it We can use the formula

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for kinetic energy to find a potential difference Kinetic energy

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goes one half mass times the square of velocity And

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we know the mass of an electron in just nine

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point one one times ten to the negative thirty one

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kilograms But we just need to solve her velocity Remember

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our earlier equation for the wavelength one that said wavelength

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equals planks constant over mass times velocity of that one

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By rearranging this we can find an equation for velocity

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Velocity equals planks constant over mass times wailing We can

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solve this equation into the kinetic energy equation can simplify

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things a little bit further to go And now it's

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Time for numbers Thanks constant is six point six three

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times ten to the negative Thirty fourth jules seconds a

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mass of an electron Is nine point one one times

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ten to the negative thirty first and the wavelength is

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sixty six Point three Pico meters are equation Looks like

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this this ugly thing right there doing the math we

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find with the kinetic energy of the electron equals five

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point four nine times ten to the negative seventeen jewels

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But remember we need to find the potential difference So

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we need to divide this result by the value of

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an electron volt find the voltage We do that and

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we get our potential difference of three hundred forty three

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electrons Bowls correct answer is and after questions like this

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we wonder who has the time to be an evil

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genius Yeah we're in all this stuff and come up

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with a plan to rule the world really where these 00:03:08.36 --> [endTime] keys in them