[4.分别光挪( Diffraction Gratings.) “历史”的回顾: 例题.N个同方向、同频率的谐振动,振幅相等 相位依次相差α,求合振动的振幅与相位。 x =a cos ot M x=a cos( at+a x =acos(at+2a) xa =a cos(at +3a) 4 ●●●。● ●●● 20 c c X 01 Pⅹ
4. 衍射光栅（Diffraction Gratings） “历史”的回顾： X 例题. N个同方向、同频率的谐振动，振幅相等 相位依次相差，求合振动的振幅与相位。 x acost 1 = cos( ) x2 = a t + cos( 2 ) x3 = a t + cos( 3 ) x4 = a t + a1 a5 a4 a3 a2 ………. O X a1 a5 4 2 a3 a2 A P Q M R C N a4 3
结论:-)当a2mnr 1:(m≠k)A=0 N 1)m=1.2.3.Ny-1 N+1.N+2.…2N-1 3N+1,3N+2,…4N-1 ●●●●●●●●●●●●0●●●0●●●●●●●●●●●●●●●。● A=0 2)在两个最大之间有N-1个最小值A=0 m=0.N2N,3N 相当于k=1,2,3 二)当a=2K时:(/=0±1±2±…) A=M 请大家记住这一结论!
结论: ( k) N m A = 0 N m 2 一）当 = 时: N +1,N + 2, 2N −1 3N +1,3N + 2, 4N −1 ……………………………... A = 0 m = 0,N,2N,3N 1) m =1.2.3....N −1 2) 在两个最大之间有N-1个最小值A=0 相当于 k =1,2,3 请大家记住这一结论! A = Na 二)当=2K时: (k = 01 2)
An array ofn parallel equidistant slits, called a diffraction grating Gratings are made by ruling equally spaced parallel grooves on a glass plate, using a diamond cutting point motion. a— width of a transparent slit a b— width of a opaque strip d--grating constant b d=a+b d:105~106m (1cm contains 100010000 slits
a b An array of N parallel equidistant slits, called a diffraction grating. Gratings are made by ruling equally spaced parallel grooves on a glass plate, using a diamond cutting point motion. a — width of a transparent slit b — width of a opaque strip d — grating constant d=a+b d：10-5～10-6m (1cm contains 1000 ～10000 slits）
Device and phenomenon装置和现象 S D 中央 L1、L2:lens透镜 明纹 A: granting光栅 Characteristics of fringes: E screen 屏幕 bright、 sharp scattered 条纹特点:亮、细、疏
S Device and phenomenon 装置和现象 L1 E A：granting 光栅 E：screen 屏幕 L1、L2 : lens 透镜 d 中央 明纹 A f Characteristics of fringes: bright、sharp、scattered. 条纹特点：亮、细、疏. L2 D
剖面图: Y 光栅 透镜 lens granting 屏幕 screen
Y I 剖面图： 光 栅 granting 透 lens 镜 屏 幕 screen