Optics: Fresnel diffraction - adjustable slit Instructor: Shaoul Ezekiel View the complete course: ocw.mit.edu/RES... License: Creative Commons BY-NC-SA More information at ocw.mit.edu/terms More courses at ocw.mit.edu
Пікірлер: 16
@sadiqsaleem58837 жыл бұрын
I think Fresnel did not used any type of lens in his experiment but Fraunhofer used two lenses to make the beam of light parrallel so that the distance between light source and the screen could be infinity. We get the fringes because of the constructive and destructive interference and can be observed by the help of Michelson interferometer. #Feedback_Please :)
@VineetBhakhar7 жыл бұрын
Stunning!
@hamdaniyusuf_dani9 жыл бұрын
I think the fringes in so called Fresnel diffraction here are actually interference pattern between direct light beam and specularly reflected light beam by the edges of the slit, just like the case of Lloyd's mirror.
@volkerblock3 жыл бұрын
No!!!!!
@hamdaniyusuf_dani3 жыл бұрын
@@volkerblock There's also light beams diffracted by each edges that contribute to the interference pattern.
@vujean86705 жыл бұрын
That was awesome
@vrindaasokan90629 жыл бұрын
Mr.Shaoul Ezekiel, why are we using a short focal length lens?
@darranedmundson15052 жыл бұрын
He wants a bright point source of illumination. Without the lens, almost all of the light wouldn’t hit the pinhole. The effect on the screen would still be there … but it would be so dim as to be invisible.
@alfredli4032 Жыл бұрын
@@darranedmundson1505 The primary reason use a lens here is considering the same observation distance, the Fresnel diffraction pattern has a significantly smaller size than Fraunhofer diffraction pattern which makes it very hard for clealy demonstration with a camera at that time. A short focal length lens is employed precisely to "unfold" the diffraction pattern on the screen. Additionally, placing the slit behind the pinhole ensures that the incident wave at the entrance surface of the slit still is a spherical wave. Imrovements of the brightness is just a side effect.
@nazmulhasanshadhin24896 жыл бұрын
Can I use a laser pointer of 650 nm wavelength to do the experiment??
@volkerblock3 жыл бұрын
yes
@volkerblock3 жыл бұрын
You can also carry out the experiments yourself at home with the simplest means (green laser pointer and simple slot). A Cornu-Sparale also shows where the dark stripe in the middle comes from. Unfortunately in German, I'm sorry, just turn off the sound.