菲涅耳衍射（ppt课件）.ppt

惠更斯-菲涅耳原理
夫琅禾费单缝衍射
夫琅禾费圆孔衍射
光学仪器的分辨本领
圆孔和圆屏菲涅耳衍射、波带片
位移-相移定理
一维光栅、二维光栅
三维光栅—X射线晶体衍射
第五章光的衍射 Diffraction
Diffraction
Light does not always travel in a straight line.
It tends to bend around objects. This tendency is called "diffraction.“
Any wave will do this, including matter waves and acoustic waves.
Shadow of a hand
illuminated by a
Helium-Neon laser
Shadow of a zinc oxide
crystal illuminated by a
electrons
Why it’s hard to see diffraction
Diffraction tends to cause ripples at edges. But poor source temporal or spatial coherence masks them.
Example: a large spatially incoherent source (like the sun) casts blurry shadows, masking the diffraction ripples.
Untilted rays yield a perfect shadow of the hole, but off-axis rays blur the shadow.
Screen
with hole
Diffraction of a wave by a slit
Whether waves in water or ic radiation in air, passage through a slit yields a diffraction pattern that will appear more dramatic as the size of the slit approaches the wavelength of the wave.
Diffraction of ocean water waves
Ocean waves passing through slits in Tel Aviv, Israel
Diffraction occurs for all waves, whatever the phenomenon.
Light passing by edge
Diffraction by an Edge
Electrons passing by an edge (Mg0 crystal)
x
Transmission
Even without a small slit, diffraction can be strong.
Simple propagation past an edge yields an unintuitive irradiance pattern.
When the wavelength is km long, a mountain peak is a very sharp edge!
Another effect that occurs is scattering, so diffraction’s role is not obvious.
Radio waves diffract around mountains
概论:
Diffraction: Example
Fresnel Diffraction from a single slit: near field and far field
Far from the slit
z
Close to the slit
Incident plane wave
Slit
在OPPO(澳宝)的内部,由无数规则的二氧化硅球粒一间隙形成了很多的三维衍射光栅,当光线射入到欧泊石内部时,出现了光线的衍射作用,衍射的角度随波长的变化而变化,从而在不同的角度可见不同的颜色,亦就是所谓的变彩。
光的衍射:当光波遇到障碍物时,会偏离几何光学的直线传播而绕行的现象称为光的衍射(diffraction of light).