1 1.the Doppler effect 2.the nature of light, wave-particle duality 3.Light as electromagnetic waves 4.Coherent light, Interferences of light

2 Optical Path Length （光程） Path length: f light

3 Young’s Double-Slit Experiment （杨氏双缝试验）

4 Optical Path Difference in Double-Slit Experiment

5

6 Case 1: interfere constructively bright fringes （亮纹） Case 2: interfere destructively dark fringes （暗纹）

7 Order Number of Bright Fringes （亮纹的级数） y = 0, central bright fringe （中央亮纹） m = 0: zeroth-order maximum （零级极大） m is called order number. y = λ L/d, first-order maximum （ m 称为级数） ( 一级极大 )

8 Spatial Distribution of the Interference Fringes Bright Fringes Dark Fringes angular positions （干涉条纹的空间分布）

9 Intensity Distribution of the Double-Slit Interference Pattern （双缝干涉图样的强度分布）

10 Monochromatic light （单色光） As discussed above. White light （白光） All bright fringes except the central one are chromatic. About the Light Source The position of the bright fringes: （除了中央亮纹，其他亮纹都是彩色的）

11 Question If there exists medium in space, the refraction index of which is n, what are the positions of the bright and dark fringes?

12 Lloy d’s Mirror （劳埃德镜） Dark fringe is found at p’ due to π- phase shift.

13 Fresnel’s Double-Mirror （菲涅尔双镜） Interference pattern can only be observed in dark zone. （只有阴影区域可以观察到干涉图样）

14 Interference in Thin Films （薄膜干涉） film air

15 Lenses do not influence the optical path difference （透镜不引起附加的光程差）

16 interfere constructively bright fringes interfere destructively dark fringes interferences of equal inclination （等倾干涉）

17 L P Planar light source mirror Thin film lens Viewing screen Pattern Bright/dark fringes

18 The Interferences of Equal Inclination （等倾干涉） 1.The fringes are rings with a common center 2.The distance between the adjacent fringes is not uniform 3.The order number reaches its maximum at the center. （干涉条纹是同心圆环） （相邻条纹的间距不相等） （中央条纹的级数是最大的）

19 Interferences of Transmission （透射光的干涉） For a given incident angle, if the reflected light interfere to produce bright fringes, then the transmitted light produce dark fringes.

20 Interference in a Wedge-shaped Film

21 Wedge with very small θ Light source lens mirror microscope

22 bright fringes dark fringes

23 Discussions on Wedge-Shaped Film Case1: h = 0dark fringes Case 2:bright fringes height difference between adjacent bright fringes: So, the distance between two adjacent bright fringes is

24 The total number of bright fringes which can be observed thus can be obtained as And it is easily to find the fringes are spaced uniformly. （易得，条纹是均匀分布的） （在劈尖上能够观测到的亮条纹的条数可以计算如下） The interference in a wedge-shaped film is called interference of equal thickness for the obvious reason. （劈尖上的干涉被称为等厚干涉）

25 Quick Quiz What if? (1) What happens to the fringes if the upper (lower) surface of the wedge-shaped film moves upward a little. (2) What happens if the angle of the wedge-shaped film increases.