Light is an amazing form of energy thatflies through our world at an incredible speed: 300,000 kilometers per second - this is enough to fly from the Sun to the Earth in just 8 minutes. We see the world around us because our eyes are complex light detectors: they constantly pick up light rays reflected from nearby objects, as a result of which the brain can create an ever-changing picture of the world around it. The only problem is that the brain is not able to keep a constant record of what the eyes see. We can recall what we thought we saw and recognize the images that we saw in the past, but we cannot easily recreate the images intact as soon as they disappeared from sight.
Is it possible to save a ray of light?
How many holograms are in your wallet? If you have any money, the answer will probably be: “pretty much.” Holograms are shiny metal patterns with ghostly images inside banknotes that help fight counterfeiters, as they are very difficult to reproduce. Credit cards also have holograms. But why else can holograms be used?
In the 19th century, ingenious inventors helpedsolve this problem by discovering a way to capture and store images on chemically treated paper. Photography, as you know, revolutionized the way we see the world and interact with it - and it gave us fantastic forms of entertainment in the 20th century in the form of films and television. But no matter how realistic or artistic the photograph may look, there can be no talk of its reality. We look at the photograph and instantly see that the image is a frozen story: the light that captured objects in the photograph disappeared a long time ago and can never be restored.
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What is a hologram?
Holograms are a bit like timeless photographs. This is a kind of “photographic ghosts”: they look like three-dimensional photographs that somehow fell into a trap inside glass, plastic or metal. When you tilt the hologram of a credit card, you see an image of something like a bird moving “inside” the card. How does it get there and what makes the hologram move? How does it differ from ordinary photography?
Suppose you want to photograph an apple. You hold the camera in front of you, and when you press the shutter button to take a picture, the camera lens opens briefly and lets in light to get on film (in an old-fashioned camera) or on a photosensitive image sensor chip (chip in a digital camera). All the light coming from the apple comes from one direction and falls into one lens, so the camera can record only a two-dimensional picture of light, darkness and color.
If you look at an apple, something happensanother. Light is reflected from the surface of the apple into both of your eyes, and the brain merges them into one stereoscopic (three-dimensional) image. If you turn your head slightly, the rays of light reflected from the apple will move along slightly different paths to meet your eyes, and parts of the apple may now appear lighter, darker, or even be of a different color. Your brain instantly recounts everything and you see a slightly different picture. That is why the eyes see a three-dimensional image.
A hologram is a cross between what happens when you photograph and what happens when you look at something real. Like a photograph, A hologram is a constant recording of light reflected from an object. But the hologram also looks real and three-dimensional and moves when you look around it, just like a real object. This is due to the unique way holograms are created.
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How to make a hologram?
You can create a hologram by reflecting the laser beam fromthe object you want to capture. In fact, you divide the laser beam into two separate halves, shining it through a half-mirror (a piece of glass coated with a thin layer of silver, so that half of the laser light is reflected and half passes through it). One half of the beam is reflected from the mirror, hits the object and is reflected on the photographic plate, inside which a hologram will be created. This is called an object beam. The other half of the beam is reflected from another mirror and hits the same photographic plate. This is the reference beam. A hologram is formed where two rays in the plate meet.