14. In a photoelectric experiment in which a sodium surface is used, one finds the maximum kinetic energy of photoelectrons is 0.62 eV for a wavelength of 4000 人，find the cutoff wavelength for sodium?

10. A stationary, circular wall clock has a face with a radius of 20 cm. Six turns of wire are wound around its perimeter; the wire carries a current 2.0 Ain the clockwise sense. The clock is located where there is a constant, uniform external magnetic field of 50 mT(but the clock still keeps perfect time). At exactly 1:00 p.m., the hour hand of the clock points in the direction of the external magnetic field. After how many minutes will the minute hand point in the direction of the torque on the winding due to the magnetic field?

11. Atom 1 of mass m\ and atom 2 of mass nn are both singly ionized with a charge of +q. After being introduced into a mass spectrometer and accelerated from rest through a potential difference V, each ion follows a semicircular path in a uniform magnetic field of magnitude B. What is the distance Ax between the points where the ions strike the detector?

12. One hundred turns of (insulated) copper wire are wrapped around a wooden cylindrical core of cross-sectional area 1.20x10-3 m2. The two ends of the wire are connected to a resistor. The total resistance in the circuit is 12.0 . If an externally applied uniform longitudinal magnetic field in the core changes from 1.60 T in one direction to 1.60 T in the opposite direction, how much charge flows through a point in the circuit during the change?

13. A pendulum consisting of a 0.01 kg mass is suspended from a string 0.1 m in length. Let the amplitude of its oscillation be such that the string in its extreme positions makes an angle of 11°(cosll° = 0.98) with the vertical. If its energy is quantized, what is the quantum number n (to the nearest order of magnitude)? (g = 10 m/s2) (According to this result, the quantized nature of the energy of the oscillations will not be apparent for large-scale system )

15. Consider an electron confined by electrical forces to move between two rigid “walls” separated by 1.5 A. What is the quantized energy value for the lowest stationary state?

二、問答計算題(共70分） 1.在推導氣體動力論巨觀現象與微觀行為關係式時，我們常用正立方體密閉容器當 例子。若有學生詢問其他形狀密閉容器是否適用相同關係式，你會如何回答並舉 例推導說明？（5%)

2.在推導單狹縫繞射關係式時，若有學生將狹缝視為無窮多點光源，並假設狹縫兩 端點光源到光屏上P點之光程差為2λ，之後將狹縫分成等大小的A、B兩區，因 這兩區的點光源皆對應相差1λ的光程差，為相長干涉。故學生推論光屏上P點為 亮紋，請問你會如何更正該學生的錯誤？（5%)

3.如右圖，在平面平行板上坐標x = 0的 A點，有一束窄光垂直射到板上，板 材料的折射率按公式變化， 式中n0和R為定值。光束在B點與原 方向成（X角離開平行板，試求B點的 x 坐標？ (5%)

4.如右圖所示，厚度s、半徑R、質I m的金屬圓板，在平行地面 之均勻磁場5中落下，若金屬圓板維持鉛直下落，使圓板面平 行磁極且垂直地面，假設比R小很多，重力加速度以g表示。 試求金屬圓板下落的加速度？（5%)

(1)請解出M給m之作用力？(5%)