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Bộ tài liệu bài tập tham khảo môn vật lý bậc đại học bằng tiếng anh Chapter 43 | 43.1 a 24 Si has 14 protons and 14 neutrons. b 37Rb has 37 protons and 48 neutrons. c 205Tl has 81 protons and 124 neutrons. 43.2 a Using R 1.2 fm A13 the radii are roughly 3.6 fm 5.3 fm and 7.1 fm. b Using 4.tR2for each of the radii in part a the areas are 163 fm2 353 fm2 and 633 fm2. c 37iR3gives 195 fm3 624 fm3 and 1499 fm3. d The density is the same since the volume and the mass are both proportional to A 2.3x 1017 kg m3 see Example 43.1 . e Dividing the result of part d by the mass of a nucleon the number density is 0.14 fm3 1.40 x 1047m3. 43.3 Æ lib - -pzB 2lib But AE hf so B 2RZ 6.63 x 10-34 J s 2.27 x 107 Hz _ 0 _ B 0.533 T 2 2.7928 5.051 x 10-27 J T 43.4 a As in Example 43.2 AE 2 1.9130 3.15245 x 10-8 eV T 2.30 T 2.77 x 10-7 eV. Since N and 5 are in opposite directions for a neutron the antiparallel configuration is lower energy. This result is smaller than but comparable to that found in the example for protons. .RE . c b f ---- 66.9 MHz X 4.48 m. h f 43.5 a U j B -pZB. N and S point in the same direction for a proton. So if the spin magnetic moment of the proton is parallel to the magnetic field U 0 and if they are antiparallel U 0. So the parallel case has lower energy. The frequency of an emitted photon has a transition of the protons between the two states given by AE _ E - E- _ 2pzB f h h h _ 2 2.7928 5.051 x 10-27 J T 1.65T 7 ------------------------------------ 7.02 X 10 HZ. 6.63 x 10 34 J s c 3.00x 10 8 m s . ------------ 4.27 m. This is a radio wave. f 7.02 x 107 Hz X b For electrons the negative charge means that the argument from part a leads to the m - -2 state antiparallel having the lowest energy since N and S point in opposite directions. So an emitted photon in a transition from one state to the other has a frequency AE E-x - En - 2 J h h h But from Eq. 41.22 Pz - 2.00232 - - 2-00232 gn 2me 4me 2.00232 eB 2.00232 1.60 x 10-19 C 1.65 T 4nme 4n 9.11 x10-31 kg f 4.62 x 1010 Hz so X This is a microwave. c _ 3.00x 108 m s f 4.62 x 1010 Hz 6.49
