電磁波基本性質實驗

1. 電磁波基本性質實驗 • Bragg Diffraction (布拉格繞射) • Fiber Optics(光纖光學)

2. Bragg Diffraction (布拉格繞射) • 由相鄰兩晶面所反射出來的電磁波之波程差若為 2dsin，其中d 為晶面距離，為入射波與晶面之間夾角，則建設性干涉的條件為波程差恰好為波長λ的整數倍 : 2dsin = nλn = 1, 2, 3 … 布拉格定律(Bragg’s Law)

3. Diffraction of X-Rays by Crystals Laue pattern

4. Laue Pattern for Beryl(Beryllium aluminum silicate)

5. Laue Pattern for enzyme Rubisco

6. z y x Crystalline structure of Nacl Na+ Cl- Fig. 27-27, p. 920

7. 晶面之指數(Miller indics) • 晶面上的三點決定晶面之指數(Miller indics) • 三個晶軸與晶面交接點(截距) • 取截距倒數 • 化成最小整數比

8. ( 1 0 0 )平面 z y ( 2 0 0 ) 平面 ( 1 0 0 ) 平面 x

11. ( 1 1 0 )平面 z y x

12. ( 1 1 1 )平面

13. Bragg Diffraction (布拉格繞射)  2  2dsin = nλn = 1, 2, 3 … Fig. 27-28, p. 920

15.    2 發射器 2dsin = nλn = 1, 2, 3 … Grazing angle d 接收器 接收器

17. (210)面 1 2

18. Fiber Optics(光纖光學) • 利用細長柔軟纖維(由玻璃、塑膠或其他透明材料製成)傳送光信號的技術 • 光波由纖維絲的一端進入後，由於全反射作用，將纖維絲方向傳輸而不從周壁逸出

19. Snell’s Law of Refraction • Snell’s Law • n1 sin θ1 = n2 sin θ2 • θ1 is the angle of incidence • θ2 is the angle of refraction n1 n2

20. Total Internal Reflection • A phenomenon called total internal reflection can occur when light is directed from a medium having a given index of refraction toward one having alower index of refraction

21. Critical Angle • There is a particular angle of incidence that will result in an angle of refraction of 90° • This angle of incidence is called the critical angle, θC

22. Optical Fibers • An application of internal reflection • Plastic or glass rods are used to “pipe” light from one place to another • Applications include • medical use of fiber optic cables for diagnosis and correction of medical problems • Telecommunications

23. Optical Fibers, cont • A flexible light pipe is called an optical fiber • A bundle of parallel fibers (shown) can be used to construct an optical transmission line

24.   接收器 R-d 發射器

26. End of the Lecture

27. Optical Fibers, cont • A flexible light pipe is called an optical fiber • A bundle of parallel fibers (shown) can be used to construct an optical transmission line

28. Construction of an Optical Fiber • The transparent core is surrounded by cladding • The cladding has a lower n than the core • This allows the light in the core to experience total internal reflection • The combination is surrounded by the jacket

29. Multimode, Stepped Index Fiber • Stepped index comes from the discontinuity in n between the core and the cladding • Multimode means that light entering the fiber at many angles is transmitted

30. Multimode, Graded Index Fiber • This fiber has a core whose index of refraction is smaller at larger radii from the center • The resultant curving reduces transit time and reduces spreading out of the pulse

31. Optical Fibers, final • Optical fibers can transmit about 95% of the input energy over one kilometer • Minimization of problems includes using as long a wavelength as possible • Much optical fiber communication uses wavelengths of about 1300 nm.

32. Total Internal Reflection (Critical Angle) • There is a particular angle of incidence that will result in an angle of refraction of 90° • This angle of incidence is called the critical angle, θC

33.   R-d 產生Total Internal Reflection

36. Fig. 25-28, p. 856

37. Fig. 25-29, p. 857

38. Fig. 25-30, p. 857