l15 - Today Announcements: HW#7 is due by 8:00 am Wednesday...

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ISP209s8 Lecture 15 -1- Today • Announcements: – HW#7 is due by 8:00 am Wednesday March 12th. – The fourth extra credit problem (Spring Break Story) is due March 19 at 8:00am – Exam #2 Review Sheet is available on-line • Quantum Mechanics •W e ak Fo r c e • Strong Force
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ISP209s8 Lecture 15 -2- Two-slit interference of electrons or photons If we cover one slit we get just one spot. This means that somehow, the photons sample all possible paths. How can a particle interfere with itself? This implies the particle, somehow, takes more than one path at the same time. The particle goes through both slits!
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ISP209s8 Lecture 15 -3- Heisenberg’s Uncertainty Principle • If a particle has a wavelength, its position and speed are not perfectly defined. • Uncertainty Principle: It is not possible to know exactly the position and momentum of a particle at the same time. • There is no absolute knowledge. The Newtonian view of the world (if everything were known, everything could be predicted) in not attainable. π 4 h p x x amplitude
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ISP209s8 Lecture 15 -4- Uncertainty depends on mass momentum electron baseball, highly exaggerated (by 10 25 ) proton position
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ISP209s8 Lecture 15 -5- Quantum Nonlocality After interaction the wave functions are entangled . If we measure 1 and 2 at the same time the difference in position forms an interference pattern. If we measure 2 before 1, the measurement of 2 defines where 1 must hit. This information travels faster than the speed of light. This has been confirmed experimentally. 2 1 1 2 Interaction
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ISP209s8 Lecture 15 -6- From large to small Atomic Nucleus Atoms A proton (uud) Made of neutrons and proton. Size 10 -14 m Made of quarks: Size 10 -15 m A neutron has ddu Made of nuclei and electrons. Size: 10 -9 m
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ISP209s8 Lecture 15 -7- There are two more forces in nature – Strong Force Strong force
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l15 - Today Announcements: HW#7 is due by 8:00 am Wednesday...

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