Fresnel and Arago spot experiment with light sources and shadows

[Luc B]

Hello from Belgium. Bruxelles.

In 1815, Fresnel made, with Arago, the experience of Poisson spot. (or Arago spot, or Fresnel bright spot). A bright point that appears at the center of a circular object's shadow due to Fresnel diffraction.
Arago and Fresnel glue a round opaque screen on a glass sheet. And use as light, the sun going through a very small hole. There are some different versions of this experience...
But photo of the round shadow and its bright central point exist... On internet.

What does have seen Fresnel if he has watched in the direction of the light, Hidden by the opaque disc.
His eye so where is the bright central point.

We can make an other experience. Now that we have camera.
Point our camera in the direction of a small light in the distance.
And occult the light at half distance with the edge of an opaque screen.
Does the light stay at the same place (in the same direction...) on the film before disappear.

Thanks for your replies.

Luc B.

 

[davenn]

But photo of the round shadow and its bright central point exist... On internet.

show us a link ... DO NOT state things like that without giving references so that people can see what you are talking about

 

[Luc B]

Hello Mr Davenn.

Sorry, but I'm not used to put internet reference in a forum. I have try. I do not had succeded.
But i have had a conversation in my inbox here with Mr Janus, Staff Emeritus. And he write to me: i quote:
"He might see a thin ring of light surrounding the disk". End quote.
"He" means Fresnel. Looking in the direction of the light, Hidden by the opaque disc.

JUst want to have the opinions of other people.
Is this enough as reference?

Luc B.

 

[Drakkith]

There should be plenty of pictures of an arago spot here.

 

[Luc B]

Hello Mr Drakkith.

Thank for your collaboration. Easy way for me like this. Thank to you

Luc B.

 

[Luc B]

Hello everybody

The first Einstein ring was discovered by Hewitt et al. (1988), who observed the radio source https://en.wikipedia.org/w/index.php?title=MG1131%2B0456&action=edit&redlink=1 using the Very Large Array. This observation saw a quasar lensed by a nearer galaxy into two separate but very similar images of the same object, the images stretched round the lens into an almost complete ring.[7] These dual images are another possible effect of the source, lens, and observer not being perfectly aligned. (Wiki English).
Sorry. Now, in french...
La première observation d'un anneau d'Einstein est réalisée en 1987 au Very Large Array par un groupe de scientifiques dirigé par Jaqueline Hewitt https://en.wikipedia.org/wiki/Jaqueline_Hewitt du MIT6. Lors de l'observation, les scientifiques remarquent que l'objet MG1131+0456v présente une forme ovoïde inhabituelle. Plusieurs explications de ce phénomène sont avancées, mais seulement celle d'Einstein est retenue. L'objet est formé de l'émission radio d'un quasar qui passerait par une lentille gravitationnelle entre la Terre et la galaxie7
1987 or 1988? That is not a very important question. Human people make mistake.

Is that something to see with diffraction of Poisson spot.

I am SURE. NOTHING TO DO.

Luc B.

 

[Drakkith]

Luc, I can barely understand anything you're saying. Please try to state your questions as simply and clearly as you can. Also remember that posts should stay in english, as per the rules.

 

[Luc B]

Hello Drakkith

Oh. What must i do?
Berkerman, Staff: Mentor ask me yesterday:"Your early posts in your thread are extremely confusing for the good people who are trying to help you".
I note: the good people who are trying to help you. They do not think that i can be a good people too that try to help them. NO NO.
And today, you write: Please try to state your questions as simply and clearly as you can.

Ok Ok. Only for you Mr Drakkith.
I really think Mr Einstein was wrong.
And this is a very simple exemple.
We see the same "thing" when we look like Jacqueline Hewitt.
Than when we look in the direction of the light. In an expérience of diffraction.
But please, do not say its. They will think i am crazy. OK?

Luc B.

 

[berkeman]

Hello Drakkith

Oh. What must i do?
Berkerman, Staff: Mentor ask me yesterday:"Your early posts in your thread are extremely confusing for the good people who are trying to help you".
I note: the good people who are trying to help you. They do not think that i can be a good people too that try to help them. NO NO.
And today, you write: Please try to state your questions as simply and clearly as you can.

Ok Ok. Only for you Mr Drakkith.
I really think Mr Einstein was wrong.
And this is a very simple exemple.
We see the same "thing" when we look like Jacqueline Hewitt.
Than when we look in the direction of the light. In an expérience of diffraction.
But please, do not say its. They will think i am crazy. OK?

Luc B.

Yikes, there is much more than a (manageable) language barrier issue here. Thread is closed for Moderation...