*cough*
Hi everyone welcome back to Cody's lab so today, I'm actually gonna be
Taking the lens off my camera and replacing the lens
with a solid disk of metal in this case a
U.s.. $1 coin
This is going to form an aragoscope, basically a telescope that does not use lenses or mirrors
So the first thing I've done is I've taped a piece of wire to the coin
Just like that
making sure not to get any
pieces of tape hanging over the edge because I want this to be a
perfectly smooth circle the wire coming off is actually going to cause issues, but just
Having it in one place is not gonna
ruin the thing next thing I need is something to look at and so I'm gonna use this bright flashlight
Which I'm setting on top of that post
And I'm gonna walk across this field
Now that I'm on the far side of the field. I'm far enough away that that light now approximates a point source
So i'm going to attach this coin to this post right here
Now I've got to do is travel back about 20 feet and line that light up with the coin
So this is with the lens on and from this vantage point as I move the camera into the shadow of the coin
You can see the light does not completely go away
In fact it looks like there's still a slightly dimmer light there
Move it out. You get the full brightness of the light go back in
You get something
Now let's take a picture without the lens on the camera
So this is what the camera sees and as I bring it into the shadow of the coin.
You can see there's a bright spot in the middle of the shadow.
This is in fact an Arago spot.
What you're seeing here is proof that photons
do not travel like bullets
They travel sort of in waves
And waves can curve around the edges of an object, and if you put a detector at the right spot
those waves converge together and
create an image
In fact what you're seeing here is an image of the lens of
the light. so you're seeing the light source here magnified quite a lot
you can also see the
Wire holding the coin and the distortion that it's causing
That's not too bad
Now to prove it let's actually go add something to the light
To make it a little bit more recognisable of a shape
Let's just try a couple of pieces of tape in a cross pattern
There's a lot less light coming through now mostly because the flashlights battery is going dead and
So I wasn't able to film it at 30 frames per second, but here is a single frame four second long exposure
You can clearly see that there are four dots where the light is coming through past the tape
So this is an image of the light source now. Let's try something a little bit more ambitious
How about a piece of foil with a bunch of holes that spell out Cody's lab?
Well, you can tell I definitely changed the shape of the image
But it's still very blurry is just too small and the resolution not enough to make out any of the actual dots and certainly not
Enough to read the word we can get better resolution by using a larger disk
This is essentially the same as getting a telescope with a bigger aperture
Okay fresh battery in the light
And I've got a bigger disc here. This is a
canning jar lid, wide mouthed, so it's quite a bit larger than the coin
To give us some better resolution
Unfortunately it means. I'm also going to have to travel farther back away from it.
98
99
100
In case you're wondering why I'm using feet and not the metric units
My shoes are 12 inches long. It's very convenient
This is what I came up with the image is pretty blurry
I think this is mostly because
Of the fact that I had to leave the shutter open for 30 whole seconds to gather enough light density
Variations in the atmosphere due to the wind
caused the image to jitter around a bunch and this kind of smeared it out across the
sensor
Also, I probably could have been better with my focal length measurements
But the fact that you can actually read this two inch long word from a distance of nearly 700 feet
Using a metal lid as a lens
It's just simply astonishing. I don't even think my six inch telescope could manage this
So it seems that this imaging technique could indeed be used to make a telescope
quite a powerful one in fact
Thought about using it to actually look at stars or something
but I ran into some problems first of all it's a little bit cloudy
And stars have a tendency to be rotated out of view and this thing is very hard to aim because it magnifies it so much
City lights are kind of similar to stars
And they don't move around so I decided to try focusing on those and see if I can magnify it and I think I could
You know just positioning my eye into the shadow I was able to get some lights to you know do the thing where they aren't
Blocked when you put the shadow on it
But when I put the camera on there it you know that the exposure took so long and really
If you think about it if the city is more than six miles away from you
There's more air between you and them than there is between you and space and I was too having problems with the air moving around
with just 700 feet
But nine miles between me and the object I'm looking at and now
It just moves all over the place is completely impossible to image
but it would definitely work in space in fact Nasa has been looking into using this as a
new Space, Telescope, and I think it definitely work you put a
Disk this lightweight, but really large you get the equivalent of a telescope with a really large aperture
So not only would it be cheap to launch but also
incredibly powerful
Anyway after my little teaser that I put at the end of one of my videos
Link in the description
many people have
thought that I got this idea from a veritasium video I
Didn't but I did go back and watch that video great video
He explains it very well in fact if you want to know more about how this works
I definitely recommend you go watch it. While your at it
I recommend another video to watch is "How far can Legolas see" by minutephysics
I'll put the links down in the description
I think that'd be good to watch to understand this video a little bit better. It was kind of funny
I think me and him must have read the same set of source material
Except that I kind of
Caught the whole thing about the light source needing me far away
Not the shadow far away
So he got that wrong, but anyone can do that. It is much easier to do it with lasers
It's much more forgiving because the laser light is already a plane wave it's all. It's already all coming
in phase
So it's kind of like a laser is a point source
At infinity even though the laser might be close
Seems fitting that I'm filming this video so close to Halloween, you know, out in the middle of no where
In total darkness with artificial light
Earlier when I was actually filming the experiment I was constantly checking with my light to see if I could see the eyes of coyotes
I mean there's cougars out there too but
cougars, the mountain lions they don't scare me so much because
They don't hunt in packs, (but) the coyotes I've seen what they do to deer
Anyway hope ya'll enjoyed. I'll see you next time