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ฟิสิกส์โอลิมปิก วิทยาศาสตร์โอลิมปิก ข้อสอบแข่งขัน ข้อสอบชิงทุน => GRE - Physics => Topic started by: conantee on January 08, 2010, 02:16:00 AM



Title: GR8677.099
Post by: conantee on January 08, 2010, 02:16:00 AM
99. The positronium "atom" consists of an electron and a positron bound together by their mutual Coulomb attraction and moving about their center of mass, which is located halfway between them. Thus the positronium "atom" is somewhat analogous to a hydrogen atom. The ground-state binding energy of hydrogen is 13.6 electron volts. What is the ground-state binding energy of positronium?
(A) (\frac{1}{2})^2 \times 13.6 \mbox{ eV}
(B) \frac{1}{2} \times 13.6 \mbox{ eV}
(C) 13.6 \mbox{ eV}
(D) 2 \times 13.6 \mbox{ eV}
(E) (2)^2 \times 13.6 \mbox{ eV}