複選題

15. Now, we have two electrons whose orbital angular momentum quantum numbers are 1 and 3, respectively. Choose the correct answers.

(A) The possible TOTAL angular momentum quantum number J can be 1

(B) The possible ORBITAL angular momentum quantum number L can be 1

(C) The possible SPIN angular momentum quantum number S can be 1 

(D) The possible MAGNETIC quantum number of total angular momentum number $m_{j}$ can be $\frac{1}{2}$

(E) The possible spin multiplicities for this two-electron system are singlet and triplet.

複選題16. We usually need to use the concept of "effective mass" to analyze and predict the properties of electronic and optoelectronic devices. It can be calculated by $\frac{1}{m^{*}} = \frac{1}{h^{2}}\frac{\partial^{2}E(k)}{\partial k^{2}}$, where $m^{*}$ is the effective mass, and $E(k)$ is the energy of the carrier as a function of the wave vector $k$. The effective mass of carriers in a material can be measured using the cyclotron resonance method. In short, this method is performed by applying a magnetic field to the material and irradiating it with electromagnetic waves, assuming that the absorption frequency of the sample matches the cyclotron frequency of the carriers in the magnetic field. Hint: You may start the derivation from the classical equation of motion of a charged particle in a magnetic field. The magnetic force is $qvB$, where $q$ is the carrier charge, $v$ is its velocity, and $B$ is the magnitude of the magnetic field, and it provides the centripetal force for circular motion ($F = \frac{m^{*}v^{2}}{r}$). Please choose the correct answer. (A) The idea of effective mass is only needed for semiconductors. For metals, the free electron model is sufficient. (B) Effective mass can be less than $m_e$, where $m_e$ is the mass of an electron. (C) The effective mass is determined by the curvature of the energy band E(k). (D) When the magnetic field is $0.15\mathrm{T}$ and the absorption frequency $= 2.1\times 10^{10}\mathrm{Hz}$, the effective mass of an electron is $0.3m_e$. (E) If the absorption frequency is $1.4 \times 10^{10} \mathrm{~Hz}$ and the radius is $3.4 \times 10^{-7} \mathrm{~m}$, the velocity of the electron should be $3 \times 10^{4} \mathrm{~m/s}$.

複選題17. A beam of neutrons is traveling at a speed of $v = 800 \, \mathrm{m/s}$ and is directed through a single slit of width $a = 1.0 \, \mu \mathrm{m}$. Given the Planck's constant $h = 6.626 \times 10^{-34} \, \mathrm{J} \cdot \mathrm{s}$ and the neutrons have mass $m_{n} = 1.675 \times 10^{-27} \, \mathrm{kg}$. Consider the neutrons as free quantum particles and their wave-like behavior. Which of the following statements are correct? (A) The de Broglie wavelength of the neutrons is approximately $4.945 \times 10^{-10} \, \mathrm{m}$. (B) The first minimum of the diffraction pattern on a screen far away from the slit occurs at an angle $\theta$ given by $\sin \theta = \lambda / a$. (C) The phase velocity of the neutron wave is greater than the speed of particles. (D) The group velocity of the neutron wave packet is equal to the speed of the particles. (E) The uncertainty in the neutron's transverse momentum due to the slit is approximately $6.63 \times 10^{-28} \, \mathrm{kg} \cdot \mathrm{m/s}$.

複選題18. Which of the following statements are correct? (A) According to the Bragg's law, when monochromatic X-rays of wavelength $\lambda = 0.154\,\mathrm{nm}$ are incident on the crystal with lattice spacing $d = 0.5\,\mathrm{nm}$, the first-order diffraction angle $\theta$ is approximately $18^{\circ}$. (B) A spectrometer on Earth with a detection limit of $0.5\,\mathrm{nm}$ can be used to detect the difference between classical and relativistic Doppler's shifts of a star moving toward Earth at a speed of $6\times 10^{6}\,\mathrm{m/s}$ and emitting light at a wavelength of $500\,\mathrm{nm}$. (C) For a free particle in one dimension with the time-dependent Schrödinger wave function $\psi(x,t) = Ae^{i(kx - \omega t)}$, the probability density is independent of time. (D) In the Compton scattering, a photon scattered by a free electron will generally emerge with a longer wavelength if it is deflected through a larger angle. (E) A particle whose wave function is a perfect plane wave has a precisely defined momentum.

複選題19. Consider 2 quantum, spin-1/2, non-interacting electrons in a 1D box. Let the box width L. Let n = quantum number of the one-electron energy eigenstate with, for example, n = 0 for the ground state, n = 1 for the 1st excited state, and so on. Denote the two-electron state by $(n_1, n_2)$, where $n_1$ and $n_2$ are the quantum numbers of the one-electron states occupied. Which of the following statements are correct, regarding the two-electron state? (A) The ground state is given by $(n_1 = 0, n_2 = 0)$. (B) The first excited state is given by $(n_1 = 0, n_2 = 1)$. (C) The two spins in the state $(n_1 = 0, n_2 = 0)$ are anti-parallel. (D) The two spins in the state $(n_1 = 0, n_2 = 1)$ can be either parallel or anti-parallel. (E) The two spins in the state $(n_1 = 1, n_2 = 1)$ can be either parallel or anti-parallel.

複選題20. Which of the following statements are wrong, for a particle totally confined in a 1D asymmetric, piecewise constant potential V(x). (A) The ground state wave function is even in parity. (B) The probability vanishes at infinity. (C) The first excited state is odd in parity. (D) The quantization leads to discrete energy levels. (E) The ground state is non-degenerate.

1. 工廠意外事故的原因，人為的失誤比機械設備所產生的意外為多。 (A)O(B)X

2. 機械產品的創新設計成為當今產品市場競爭的主力，鉗工技術也成為原型開發的核心技術。 (A)O(B)X

3. 依 CNS 標準，圖面符號◎表示真圓度。 (A)O(B)X

4. 工件劃線後常使用中心衝在線上作標記，以防線條的磨除、脫落而不清。 (A)O(B)X

5. 握持手錘(榔頭)錘擊時，五指要緊握錘柄，以防震動、鬆脫而滑離。 (A)O(B)X

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