Chapter2_18 - no light(or anything else can escape i.e...

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PHY3063 R. D. Field Department of Physics Chapter2_18.doc University of Florida Black Holes Consider the light emitted from a massive star with star star star R GM V = and suppose that the light is moving away from the star and heading to a point where V g = 0. In this case we have 0 2 2 1 f c R GM f star star = where f 0 is the frequency of the light at the surface of the star and f is the frequency of the light a long distance from the star ( i.e. at V g = 0). At 1 2 2 = c R GM star star the frequency f = 0 which corresponding to photon with no energy ( i.e. the photons do not have enough kinetic energy to escape the star). If we define 2 2 c GM R star hild schwartzsc = , then for R R schwartzschild
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Unformatted text preview: no light (or anything else) can escape ( i.e. Black Hole!). Also at R = R schwartzschild time at the surface of the star stops moving since t at the surface is given by τ 2 2 1 c R GM t star star − = . Classical Escape Velocity: In classical physics the minimum velocity for a mass m to escape the gravitational attraction of a massive star is given by solving the following: 2 1 2 = = − = final star star initial E R GmM mv E . Thus, star star escape R GM v 2 = and R star = R schwartzschild implies v escape = c! Massive Star M star R star Direction of light V star Schwartzschild Radius...
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