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Lecture

# Oct.4 - 2B03.docx

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School
Department
Astronomy
Course
ASTRON 2B03
Professor
Laura Parker
Semester
Fall

Description
Oct. 4 – 2B03 04/10/2011 9:24:00 AM Novel Prize – evidence for the acceleration of the expansion of the universe.  Used standard candles. Special relativity – associated w/ very fast speeds. More waves per unit time – blueshift Less waves per unit time – redshift  Speed stays constant, what changes is wavelength. Let’s Look at Small Things  In quantum mechanics, we will look deeper into the atom. Quarks are the units that made protons and neutrons. Classical Physics  Momentum (p) = mv o Falls apart in quantum world. Quantum Physics  Newton’s Laws breaking down at extreme cases (moving incredibly fast). Also, at really small scales (atom’s size).  Blackbody radiation – main point – hot objects glow w/ a spectrum of colours that depend only on their temperature. o Colour depends only on temperature. o From colour you see, you can work out temperature. o Stars – excellent blackbodies. You can tell from its colour what temperature it is. o If light comes in packets of quanta, you can understand the diagram. Einstein also made huge contributions to quantum mechanics.  Built on Planck’s ideas. People thought light was continuous wave – but it was discovered that light comes in little particles. He could now describe the photoelectric effect. We thought that in order to move stuff around, we needed momentum. SOme mass and some velocity. But light has no mass, photons got none. Our idea of momentum for light must not be correct.  First evidence that classical physics was breaking down. P=mv does not work for light and subatomic particles.  Duality – light behaves as a wave and a particle. o Subatomic particles can also behave like both particles and waves. Energy realized – E=hf  As frequency increases, we have more energy. As f goes up, E goes up.  Redshifting – longer wavelength – energy smaller (photons lose energy). Another surprise  Reverse might also be true. Particles may behave as waves. Quantum Tunne
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