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PHYSICS OF THE IMPOSSIBLE
Scientists successfully demonstrated this principle with a device
made of ten fiberglass rings covered with copper elements. A copper
ring inside the device was rendered nearly invisible to microwave radiation, casting only a minuscule shadow.
At the heart of metamaterials is their ability to manipulate something called the "index of refraction." Refraction is the bending of light
as it moves through transparent media. If you put your hand in water,
or look through the lens of your glasses, you notice that water and
glass distort and bend the path of ordinary light.
The reason that light bends in glass or water is that light slows
down when it enters a dense, transparent medium. The speed of light
in a pure vacuum always remains the same, but light traveling through
glass or water must pass through trillions of atoms and hence slows
down. (The speed of light divided by the slower speed of light inside
the medium is called the index of refraction. Since light slows down in
glass, the index of refraction is always greater than 1.0). For example,
the index of refraction is 1.00 for a vacuum, 1.0003 for air, 1.5 for glass,
and 2.4 for diamond. Usually, the denser the medium, the greater the
degree of bending, and the greater the index of refraction.
A familiar example of the index of refraction is a mirage. If you are
driving on a hot day and look straight toward the horizon, the road
may seem to be shimmering, creating the illusion of a glistening lake.
In the desert one can sometimes see the outlines of distant cities and
mountains on the horizon. This is because hot air rising from the pavement or desert has a lower density than normal air, and hence a lower
index of refraction than the surrounding, colder air, and therefore light
from distant objects can be refracted off the pavement into your eye,
giving you the illusion that you are seeing distant objects.
Usually, the index of refraction is a constant. A narrow beam of
light is bent when it enters glass and then keeps going in a straight
line. But assume for the moment that you could control the index of refraction at will, so that it could change continuously at every point in
the glass. As light moved in this new material, light could bend and
meander in new directions, creating a path that would wander
throughout the substance like a snake.
PHYSICS OF THE IMPOSSIBLE
Scientists successfully demonstrated this principle with a device
made of ten fiberglass rings covered with copper elements. A copper
ring inside the device was rendered nearly invisible to microwave radiation, casting only a minuscule shadow.
At the heart of metamaterials is their ability to manipulate something called the "index of refraction." Refraction is the bending of light
as it moves through transparent media. If you put your hand in water,
or look through the lens of your glasses, you notice that water and
glass distort and bend the path of ordinary light.
The reason that light bends in glass or water is that light slows
down when it enters a dense, transparent medium. The speed of light
in a pure vacuum always remains the same, but light traveling through
glass or water must pass through trillions of atoms and hence slows
down. (The speed of light divided by the slower speed of light inside
the medium is called the index of refraction. Since light slows down in
glass, the index of refraction is always greater than 1.0). For example,
the index of refraction is 1.00 for a vacuum, 1.0003 for air, 1.5 for glass,
and 2.4 for diamond. Usually, the denser the medium, the greater the
degree of bending, and the greater the index of refraction.
A familiar example of the index of refraction is a mirage. If you are
driving on a hot day and look straight toward the horizon, the road
may seem to be shimmering, creating the illusion of a glistening lake.
In the desert one can sometimes see the outlines of distant cities and
mountains on the horizon. This is because hot air rising from the pavement or desert has a lower density than normal air, and hence a lower
index of refraction than the surrounding, colder air, and therefore light
from distant objects can be refracted off the pavement into your eye,
giving you the illusion that you are seeing distant objects.
Usually, the index of refraction is a constant. A narrow beam of
light is bent when it enters glass and then keeps going in a straight
line. But assume for the moment that you could control the index of refraction at will, so that it could change continuously at every point in
the glass. As light moved in this new material, light could bend and
meander in new directions, creating a path that would wander
throughout the substance like a snake.