Th3 - 36th International Physics Olympiad. Salamanca...

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36 th International Physics Olympiad. Salamanca (España) 2005 Th 3 Page 1 of 3 R.S.E.F. Th 3 NEUTRONS IN A GRAVITATIONAL FIELD In the familiar classical world, an elastic bouncing ball on the Earth’s surface is an ideal example for perpetual motion. The ball is trapped: it can not go below the surface or above its turning point. It will remain bounded in this state, turning down and bouncing up once and again, forever. Only air drag or inelastic bounces could stop the process and will be ignored in the following. A group of physicists from the Institute Laue - Langevin in Grenoble reported 1 in 2002 experimental evidence on the behaviour of neutrons in the gravitational field of the Earth. In the experiment, neutrons moving to the right were allowed to fall towards a horizontal crystal surface acting as a neutron mirror, where they bounced back elastically up to the initial height once and again. The setup of the experiment is sketched in Figure F-1. It consists of the opening W, the neutron mirror M (at height z = 0), the neutron absorber A (at height z = H and with length L ) and the neutron detector D. The beam of neutrons flies with constant horizontal velocity component v x from W to D through the cavity between A and M. All the neutrons that reach the surface of A are absorbed and disappear from the experiment. Those that reach the surface of M are reflected elastically. The detector D counts the transmission rate
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This note was uploaded on 11/08/2011 for the course PHYS 0000 taught by Professor Na during the Spring '11 term at Rensselaer Polytechnic Institute.

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Th3 - 36th International Physics Olympiad. Salamanca...

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