2022-2023学年高二物理竞赛课件：布儒斯特角的应用

布儒斯特角的应用 用于激光器中来减少反射损失 布儒斯特角的应用 R = 100% R = 90% Laser medium P 0% reflection P 0% reflection Incidence angle, qi Reflection coefficient, r 1.0 .5 0 -.5 -1.0 r|| r ┴ 0° 30° 60° 90° 全反射区 Critical angle θc θB Reflection Coefficients for a Glass-to-Air Interface 透射比 (T) T º 透射功率 / 入射功率 qt qi wi wt ni nt A = Area 光束的束宽 wi: 反射比 (R) R º 反射功率 / 入射功率 A = Area qi wi ni nt qr wi 由于 空气-玻璃的反射比和透射比 Note that R + T = 1 垂直偏振 Incidence angle, qi 1.0 .5 0 0° 30° 60° 90° R T 平行偏振 Incidence angle, qi 1.0 .5 0 0° 30° 60° 90° R T 玻璃-空气的反射比和透射比 Note that R + T = 1 Perpendicular polarization Incidence angle, qi 1.0 .5 0 0° 30° 60° 90° R T Parallel polarization Incidence angle, qi 1.0 .5 0 0° 30° 60° 90° R T For p light only For p and s 垂直入射时的反射系数 When qi = 0, and For an air-glass interface (ni = 1 and nt = 1.5), R = 4% and T = 96% The values are the same, whichever direction the light travels, from air to glass or from glass to air. The 4% has big implications for photography lenses. So there will be destructive interference between the incident and reflected beams just before the surface. Analogously, if ni > nt (glass to air), r > 0, and there will be constructive interference. ni nt qi qr qt Ei Bi Er Br Et Bt Interface 平行入射面偏振光的相位变化 ni nt qi qr qt Ei Bi Er Br Et Bt Interface × 平行入射面偏振光的相位变化 This also means destructive interference with incident beam. Analogously, if ni > nt (glass to air), r|| < 0, and we have constructive interference. Good that we get the same result as for r ; it’s the same problem when qi = 0! Also, the phase is opposite above Brewster’s angle. Phase shifts in reflection (air to glass) ni < nt 180° phase shift for all angles 180° phase shift for angles larger than Brewster's angle; 0° for lower angles ┴ || 0° 30° 60° 90° Incidence angle 0° 30° 60° 90° Incidence angle p 0 p 0 θB 光疏-光密介质的垂直入射或掠入射的反射光总有半波损失! Phase shifts in reflection (glass to air) nt < ni Interesting phase above the critical angle 180° phase shift for angles below Brewster's angle; 0° for larger a