22. The potential difference across a cell membrane is 64 mV. On the outside are 4.0 × 106 singly ionized potassium atoms. Assuming an equal negative charge on the inside, what is the membrane’s capacitance? Note that one elementary charge is about 1.6 × 10−19 C. (A) 1 nF (B) 10 nF (C)100 nF (D) 1 pF (E) 10 pF.

22. The potential difference across a cell membrane is 64 mV. On the outside are 4.0 × 10⁶ singly ionized potassium atoms. Assuming an equal negative charge on the inside, what is the membrane’s capacitance? Note that one elementary charge is about 1.6 × 10⁻¹⁹ C.
(A) 1 nF
(B) 10 nF
(C)100 nF
(D) 1 pF
(E) 10 pF.

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統計： A(0), B(2), C(0), D(0), E(2) #3840132

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31. With sufficient energy, it’s possible to eject an electron from an inner atomic orbital. A higher-energy electron will then drop into the unoccupied state, emitting a photon with energy equal to the difference between the two levels. For inner-shell electrons, photon energies are in the keV range, putting them in the X-ray region of the spectrum. These characteristic X-rays are labeled with the letter indicating the shell to which the electron drops, followed by a Greek letter indicating the higher level from which it drops; thus ?? designates a transition from the L shell to the K shell. Molybdenum’s X-ray spectrum has its ?? peak at17.4 keV. Note that Plank’s constant is 6.626 × 10−34 m2 ∙ kg/s, speed of light is 3 × 108 m/s, and one electron charge is 1.6 × 10−19 C. The corresponding X-ray wavelength is closest to (A) 10 pm (B) 30 pm (C) 70 pm (D) 150 pm (E) 200 pm.

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