tailieunhanh - Physics exercises_solution: Chapter 35

Bộ tài liệu bài tập tham khảo môn vật lý bậc đại học bằng tiếng anh Chapter 35 | Measuring with a ruler from both 51 and S2 to there different points in the antinodal line labeled m 3 we find that the difference in path length is three times the wavelength of the wave as measured from one crest to the next on the diagram. a At S1 r2 - r1 41 and this path difference stays the same all along the y - axis so m 4. At S2 r2 - r1 -41 and the path difference below this point along the negative y -axis stays the same so m -4. b c The maximum and minimum m-values are determined by the largest integer less d than or equal to . 1 d If d 7 1 -7 m 7 so there will be a total of 15 antinodes between the 2 sources. Another antinode cannot be squeezed in until the separation becomes six times the wavelength. a For constructive interference the path diference is ml n 0 1 2 . The separation between sources is m so for points between the sources the largest possible path difference is m. Thus only the path difference of zero is possible. This occurs midway between the two sources m from A. b For destructive interference the path difference is m 1 m 0 1 2 . A path difference of 1 2 m is possible but a path difference as large as 3X 2 is not possible. For a point a distance x from A and - x from B the path difference is x - m - x . x - m - x m gives x m x - m - x m gives x m a The path difference is 120 m so for destructive interference - 120 m 1 240 m. 2 b The longest wavelength for constructive interference is - 120 m. 2 For constructive interference we need r. - r1 m1 m - x - x m1 m1 A _ mc m 108 m s . . x m------ - m - m m . 2 2f 2 120 x 106 Hz x m m m m m m m. For m 3 2 1 0 -1 -3. Don t confuse this m with the unit meters also represented by an m . a The brightest wavelengths are when constructive interference occurs d 2040 nm 2040 nm d m1 1 13 ------------ 680 nm 1. .