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Physics exercises_solution: Chapter 42

Bộ tài liệu bài tập tham khảo môn vật lý bậc đại học bằng tiếng anh Chapter 42 | 421- a K 3kT T 2K 2 7-9 x 10-4eV 1.60 x 10-19 J eV 2 3k 3 1.38 x 10 23 J K T 6.1K b T 2 4.48eV 1.60 x -1 eVl 34 600 k. 3 1.38 x 10 J K c The thermal energy associated with room temperature 300 K is much greater than the bond energy of He2 calculated in part a so the typical collision at room temperature will be more than enough to break up He2. However the thermal energy at 300 K is much less than the bond energy of H2 so we would expect it to remain intact at room temperature. 42.2 a U ----- -5.0 eV. 4n r b -5.0 eV 4.3 eV-3.5 eV - 4.2 eV. 42.3 Let 1 refer to C and 2 to O. m1 1.993 x 10-26kg m2 2.656 x 10-26kg r0 0.1128 nm m- 1 ---2 lr0 0.0644 nm carbon m1 m2 r2 LmL_ 1r0 0.0484 nm carbon m1 m2 b I m1r12 m2r22 1.45 x 10-46kg m2 yes this agrees with Example 42.2. 42.4 The energy of the emitted photon is 1.01 x 10-5 eV and so its frequency and wavelength are f E 1.01 x 10-5eV 1.60 x 10-19J eV 2 44GHz J h 6.63 x 10-34J s . X f 3.00 x 108m s 2.44 x 109Hz 0.123 m. This frequency corresponds to that given for a microwave oven. 42.5 a From Example 42.2 E1 0.479 meV 7.674 x 10J and I 1.449 x 10 46 kg m2 K 2 Im2 and K E gives m 2E1 1 1.03 x 1012 rad s b v1 r1m1 0.0644 x 10 9m 1.03 x 1012 rad s 66.3 m s carbon v2 r2m2 0.0484 x 10 9m 1.03 x 1012 rad s 49.8 m s oxygen c T 2n m 6.10 x 10 12s 42.6 a E0 1-gm 0.2690 eV 2.083 x 10 20J r 1 2 fW 2 2.083 x 10 2J 1 ni E0 -2 mvm.x gives v 1.139 x 10-kg 91 x 10 ri s b According the Eq. 42.7 the spacing between adjacent vibrational energy levels is twice the ground state energy En n 2 nm AE En 1 En gm hf. Thus using the AE specified in Example 42.3 it follows that its vibrational period is T 1 __ 1.54 x 10-.4 f AE 0.2690 eV 1.60 x 10 19J eV c The vibrational period is shorter than the rotational period. 42.7 a I mrr2 m mH I r 2 rnLl mH J _ 1.17 x 10 kg 1.67 x 10kg 1.59 x 10 m 2 1.17 x 10 kg 1.67 x 10 kg 3.69 x 10 4 7 kg m2 AE E4 E3 i 4 4 1 3 3 1 T AE 4 1.054x 10-34J s 2 3.69 x 10 kg m2 AE 1.20 x 10 J 7.53 x .