Astro Lecture 9-3

# Astro Lecture 9-3 - Astro Lecture • • • • • •...

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9/4/07 Diurnal Parallax – from two points on earth simply too small to see for stars Annual Parallax – using of Earth’s orbit to gain a wider baseline in vantage point o Parallax decreases with increasing distance First measurement of stellar parallax o Put “nail in the coffin” of geocentric universe Parsec (Parallax of one arcsec) = 206, 265 AU Electricity and Magnetism intrinsically linked o A moving magnetic field creates electricity o Connection made by Maxwell Maxwell’s Wonderful Equations Found that there is a constant, velocity, that connects magnetism and electricity Hypothesized that light is actually an electromagnetic field Oscillating magnetic field and oscillating electric field create the electromagnetic field o Self propagating because they create one another If you increase the wavelength you decrease the frequency Unit of Frequency = (1/time) v Hertz (Hz) = (1/second) Electromagnetic Spectrum o Gamma Rays – X rays – UV- Visible – Infrared- microwave- radio frequency o Wavelength increases and frequency decreases as you move from left to right o All of these are forms of light – radio the same as the light you see, just has a different freq. and wavelength If you combine two waves at the same phase you increase the amplitude o If you send out the same wave at a different phase it will cancel out the other wave Light is also a particle o Einstein found that energy of electron liberated by light is proportional to wavelength not intensity o A photon has no mass but it does carry energy considered the birth of quantum mechanics Light carries information o light doesn't need a medium to travel in - like sound or water waves READ CHAPTERS 3 AND 4 LOOK OVER PRESENTATION AGAIN CHAPTER 4 AND 5, 17.2

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Astro Lecture 9-3 - Astro Lecture • • • • • •...

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