mPEC Forum

ฟิสิกส์โอลิมปิก วิทยาศาสตร์โอลิมปิก ข้อสอบแข่งขัน ข้อสอบชิงทุน => GRE - Physics => Topic started by: conantee on December 08, 2010, 04:46:11 AM



Title: GR9677.097
Post by: conantee on December 08, 2010, 04:46:11 AM
97. A particle of mass m has the wave function \Psi (x,t) = e^{i \omega t} [\alpha \cos (kx) + \beta \sin (kx)], where \alpha and \beta are complex constants and \omega and k are real constants. The probability current density is equal to which of the following? (Note: \alpha^* denotes the complex conjugate of \alpha, and  \left| \alpha \right| ^2 = \alpha^* \alpha.)
(A) 0
(B) \hbar k /m
(C) \frac{\hbar k}{2m} (\left| \alpha \right| ^2 + \left| \beta \right| ^2)
(D) \frac{\hbar k}{m} (\left| \alpha \right| ^2 - \left| \beta \right| ^2)
(E) \frac{\hbar k}{2mi} (\alpha^* \beta - \beta^* \alpha)