第12章波动光学概述.ppt

* 1)The reflected (反射) beam is fully polarized（S光），其振动方向垂直于入射面； 2)折射光和反射光的传播方向相互垂直. 3)The refracted (折射) beam is partially polarized（S光和P光） 。 here： §12-9 Polarization by Reflection or Refraction 3. Brewster’s Law * Example: We wish to use a plate of glass (n=1.57) as a polarizer. (1)What is the Brewater angle? That is , at what angle of incidence will the reflected beam be fully polarized? (2) What angle of refraction corresponds to this angle of incidence? * Solution: * a b ?h b a ?h ek-1 ek * 3. Circular Hole Diffraction (2) * Example: A slit of width a=2.5μm is illuminated by white light. (1) What is the diffraction angle ?1 that the first minimum for the red light λ=6500A falls at? (2) What is the wavelength λ of the light whose first diffraction maximum falls at ?1 ,thus coinciding with the first minimum for the red light? * Solution: (1) At the first minimum, from equation asin?=kλ,k=1,we have: * (2)At the first maximum, for the equation asin?=(2k+1)λ/2, where k=1, ?’= ?1 =15o, we have Therefore: * §12-7 Diffraction Grating (衍射光栅) A diffraction grating are made by ruling(划线) equally spaced parallel grooves(凹槽) on a polished(擦亮的) glass plate. The width of a groove is b.(刻痕是b，不透光), the width of a slit is a, d=a+b is called grating constant. * §12-7 Diffraction Grating (衍射光栅) * 1. grating equation P φ The optical path difference between rays from adjacent slits is (a+b)sinφ。 The φ is called diffraction angle. The grating equation is： §12-7 Diffraction Grating (衍射光栅) * (1) Primary maximum fringe(主极大条纹) 满足光栅方程的明条纹称主极大条纹，也称光谱线。 When ?=0, k=0——the central bright fringe 1. grating equation §12-7 Diffraction Grating (衍射光栅) The fringes that in accordance with the grating equation are called the primary maximum fringes, or spectrum line. * (2) The maximum order of the visible frings (3) Since 可见光栅常数越小，各级明纹衍射角越大，即各级明纹分得愈开。 可见条纹的最大级次 1. grating equation §12-7 Diffraction Grating (衍射光栅) * Example: A white light incident normally on a grating. The grating c