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Fastest-Ever Flashgun Captures Image of Light Wave
loconet writes to tell us that a team of researchers have created the shortest-ever flash of light. Weighing in at just 80 attoseconds, this flash has already been used to capture an image of a laser pulse and could possibly be used in the future to capture the electron movement around large atoms.
That's not what happens. You only see a laser because the photons reflect off particles (neon in this case). The photons which hit your camera all come from (almost) parallel lines so what you see is where the photons hit by your beam were.
No, shutters are used to limit the ambient light from reaching the film (or sensor). In a situation like this you are limiting the light being produced. So no shutter is needed - just leave the film exposed for the whole experement, when the light is produced it will be recorded (you record the rest of it too, but it records as nothing).
From the article it sounds like a pump-probe experiment. They excite the neon with a 2.5 femtosecond pulse and then image the excited state with a 80 attosecond pulse. (You obviously need the imaging pulse to be shorter than the excitation pulse.) I'm not sure how much detail you would be able to get from this though, as the wavelength and brightness of the light source would be a limiting factor.
Can't you just illuminate something brightly for any length of time when taking a picture?
Isn't shutter speed the problem?
Someone educate me. As with so many things, the laws of physics are the problem. The duration of light is the path of least resistance.
The fundamental reason behind using strobe light in photography is to freeze action.
Consider a 35mm film camera with a mechanical shutter... what degree of force and mechanism would be required to move that shutter to open AND close the height of 24mm in 80 attoseconds? IANAPhysicist, but I doubt human hands could hang on to it.
Meanwhile, I can take my old Leica*, lock the shutter open on a tripod in a dark room, and "paint" the walls with a handheld strobe. There will be no overall blur because the camera is stable, and no object blur, because the distance my cat* can run in 1/31,000ths of a second (the speed of my flash at 1/64th power) is too small to perceive.
*note I no longer have a Leica or a cat because of falling down in the dark. Don't try this at home kids.
Ok, first you have this coherent photon beam. This means that they are all traveling at the same direction. So how do you take a picture of THAT?
In a different way that a standard photograph.
You are bombarding the photon beam with photons,
No, you aren't. That doesn't make sense.
What they do is have the laser pulse travel through something they call a "chirped mirror". This packs the photos from the laser pulse into a smaller space. This then travels through a neon cloud, which then creates a flash of light. This flash of light is the "shortest-ever flash of light".
To photograph this flash of light, they direct it into a second neon cloud, which ionizes atoms, releasing electrons. Those electrons are then recorded. Multiple flashes were required to produce enough electrons to build up the image shown in the article, so what you really have is an image of many flashes overlaid.
Consider a 35mm film camera with a mechanical shutter... what degree of force and mechanism would be required to move that shutter to open AND close the height of 24mm in 80 attoseconds? IANAPhysicist, but I doubt human hands could hang on to it.
Apparently we're not realizing just how short 80 attoseconds is. You doubt human hands could hang on to it? Moving 24mm in 80 attoseconds is faster than the speed of light. Not only is it faster than the speed of light, it's a million times faster than the speed of light.
Light only travels 24 nanometers in 80 attoseconds.
ZFS: because love is never having to say fsck
Wrong, by classical double slit experiment. Single photons are fired at two slits, yet still create the double interference pattern that can only be explained by it going to through both slits as a wave would.
What? The page wasn't taken down. . . it's just that the linky is wrong. Try here
Or people who don't like to have their search results artificially curtailed by someone else's sense of unreasonable morality.
I assume you mean to use this method to determine which slit the photon passes through, which works. Sorta. Determining which slit the photon passes through can be done (not sure if by this method, but it's been done in the past), but when done all of a sudden the interference pattern vanishes. This is the source of the quantum observation effect you may have heard about.
Check out the book QED: The Strange Theory of Light and Matter, by Richard Feynman. The answer is basically that the photon doesn't bounce off of anything! It "interacts" with an electron, and another photon is emitted. Why is it emitted at the particular angle? That's what the book is all about. Way too much to explain here. But if you want to understand in layman's terms how reflection and refraction work, and why glass is transparent, get that book, it's wonderful.