91影视

Explain the dependence of conductivity on temperature for conductors and for semiconductors.

Electron affinity is a property specifying the "appetite" of an element for gaining electrons. Elements, such as fluorine and oxygen that lack only one or two electrons to complete shells can achieve a lower energy state by absorbing an external electron. For instance, in uniting an electron with a neutral chlorine atom, completing its n = 3 shell and forming a CI ion, 3.61 eV of energy is liberated. Suppose an electron is detached from a sodium atom, whose ionization energy is 5.14 eV.Then transferred to a (faraway) chlorine atom.

(a) Must energy on balance be put in by an external agent, or is some energy actually liberated? If so How much?

(b) The transfer leaves the sodium with a positive charge and the chlorine with a negative. Energy can now be extracted by allowing these ions to draw close forming a molecule. How close must they approach to recover the energy expended in part (a)?

(c)The actual separation of the atoms in a NaCl molecule is 0.24 nm. How much lower in energy is the molecule than the separated neutral atoms?

The effective force constant of the molecular 鈥渟pring鈥� in HCL is $\mathbf{480}\mathbf{鈥�}\mathbf{\text{N/m}}$, and the bond length is $\mathbf{0}.\mathbf{13}鈥�\mathbf{nm}$.

(a) Determine the energies of the two lowest-energy vibrational states.

(b) For these energies, determine the amplitude of vibration if the atoms could be treated as oscillating classical particles.

(c) For these energies, by what percentages does the atomic separation fluctuate?

(d) Calculate the classical vibrational frequency${\mathit{蝇}}_{\mathbf{v}\mathbf{h}}\mathbf{=}\sqrt{\mathbf{k}\mathbf{/}\mathbf{渭}}$and rotational frequency for the rotational frequency${\mathit{蝇}}_{\mathbf{r}\mathbf{o}\mathbf{t}}\mathbf{=}\mathit{L}\mathbf{/}\mathit{I}$, assume that L is the its lowest non zero value, $\sqrt{\mathbf{1}\mathbf{(}\mathbf{1}\mathbf{+}\mathbf{1}\mathbf{)}}\mathit{h}$and that the moment of inertia $\mathit{I}$is $\mathit{渭}{\mathit{a}}^{\mathbf{2}}$.

(e) Is is valid to treat the atomic separation as fixed for rotational motion while changing for vibrational?

Vibration-rotation spectra are rich For the CO molecule (data are given in Exercise 42), roughly how many rotational levels would there be between the ground vibrational state and the first excited vibrational state?

Assuming an interatomic spacing of 0.15 nm, obtain a rough value for the width (in eV) of the$\mathbf{n}\mathbf{=}\mathbf{2}$ band in a one-dimensional crystal.

Question: The Fermi velocity V_F is defined by${\mathbf{E}}_{\mathbf{F}}\mathbf{=}\frac{\mathbf{1}}{\mathbf{2}}{\mathbf{mv}}_{\mathbf{F}}^{\mathbf{2}}$ , where is the fermi energy. The Fermi energy for silver is 5.5eV.(a) Calculate the Fermi velocity.(b) what would be the wavelength of an electron with this velocity. (c)How does this compare with the lattice spacing of 0.41 nm? Does the order of magnitude makes sence?

Question: The critical temperature lead is 7.2 K. What is the binding energy of its Cooper pairs at zero temperature?