can light bend around corners

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So, can light really be curved by Corners?

It’s a basic question about how light behaves, and the simple answer is yes — but only if by “curved” you mean either “the appearance of being curved,” or “actually curved because of some physical law.”

When you shine a flashlight or watch sunlight streaming in a window, light generally has the appearance of going straight.

That’s a central idea in geometric optics.

Light is an electromagnetic wave, and in a uniform medium like air or a vacuum, these waves propagate in straight lines.

Think of a laser pointer; the beam shoots straight from the laser to the wall.

But light also behaves like a particle called a photon.

The fact that photons behave like particles as well as waves, a fact known as wave-particle duality, is fundamental to quantum mechanics.

Photons travel in straight lines in an open space, but when interacting with material they exhibit behavior that can result in curving, or other complicated paths.

Straight line behavior is a great approximation when the wavelength of light is substantially shorter than the objects it interacts with.

Diffraction

one of the ways that light appears to “curve” the most often is due to a phenomenon called diffraction.

Diffraction is the process where light waves interact with an obstacle, or go through a small opening.

Instead of producing just a single shadow or going right through unimpeded, the light waves diverge when encountering the boundary or opening.

Picture shooting a laser beam through a pin hole.

You won’t get a neat little dot on the wall; you’ll find a somewhat bigger, fuzzier circle with fainter rings all over.

The spreading out is diffraction.

The degree of diffraction is inversely related to the size of the opening or barrier relative to the wavelength of light.

Therefore, small openings produce greater divergence.

This is why you might hear someone talking around a corner before you see him/her; sound waves are much easier to diffuse around normal-sized objects (and have much longer wavelengths than visible light).

Noticeable diffraction is possible with visible light (with wavelengths approximately 400-700 nm), only around objects much smaller than normal sized objects or through apertures much narrower than normal (such as diffraction gratings).

Because buildings are too large relative to light’s wavelength, you wouldn’t expect to notice visible light Bending around a typical building.

Refraction

Refraction is yet another mechanism for altering the path of light. Refraction occurs when light crosses from one medium to another (for example from air into water or glass). As light moves from one medium into another, its speed changes. Therefore, as light approaches an interface between two Media, it bends toward the slower-moving medium.

Refraction explains why things appear distorted when viewed underwater, and also explains how lenses focus or disperse light. Refraction doesn’t refer to “Bending around a corner,” however. In that context, refraction refers to the change in direction of light at an interface between two clear materials. Depending upon the angle that light strikes the second medium and based on the refractive indexes of each medium involved, there will be various amounts of Bending.

Total internal reflection: creating paths of light that are indistinguishable from a curve

There exists another important mechanism for directing light down paths that could be considered “around Corners”: total internal reflection. Total internal reflection occurs when a light ray exits a denser material (such as glass) and attempts to enter a less-dense material (such as air) at an angle less than the critical angle. At this angle and below, instead of continuing on past the interface to exit the first material, the entire ray of light reflects backward into the denser material.

The principal behind fiber-optic cables relies heavily on total internal reflection. Fiber-optic cables consist of very clean glass or plastic fibers. one end of the cable receives light, which then continues to bounce back and forth off the interior surface of the fiber. Essentially, light bounces its way along the length of the cable, even when the cable turns. Because of this ability to direct light along a path that includes several curves, fiber-optics enables communications signals (such as internet signals) to travel for miles without significant loss.

Although much of the time we think of light as behaving in “straight” lines within fiber-optic cables (i.e., it follows a straight line after every reflection), ultimately, the path followed by the light as it makes its way down the fiber follows along with the curves of the fiber itself.

Engineering light’s path using metamaterials

More recently developed techniques for controlling light involve metamaterials. These materials are created specifically to control their optical properties through their structural arrangement at scales much smaller than the wavelength of light. Unlike traditional materials, whose properties depend on their chemical makeup, the properties exhibited by metamaterials arise solely from their structure.

Some metamaterials have been shown to exhibit negative refractive index. Negative refractive index was never seen before in naturally occurring materials. Materials exhibiting negative refractive index can therefore be used to deflect light in unusual ways. Some examples include “cloaking” objects by channeling light around them. While currently limited to laboratory experiments and early stages of development, researchers believe that metamaterials can eventually be used to design materials capable of creating artificial optical effects including true “light-Bending-around-Corners.”

Cosmic Curvature: gravitational lensing

Finally, on cosmological scales, light can indeed be deflected in ways that clearly warp its trajectory: gravitational lensing. According to einstein’s theory of General Relativity, massive objects (including stars, galaxies and galaxy clusters) distort spacetime. Photons traveling through this warped spacetime follow the Curvature, thus appearing to bend around large masses.

This produces a number of effects. Gravitational lensing can magnify distant sources of light (making them observable at higher brightness levels than they would normally be), distort them (stretching and compressing them), or split them into multiple images (depending upon whether the background object lies exactly at the center of mass of the foreground object, etc.).

Researchers use gravitational lensing to examine distant objects that would otherwise be too faint to view by astronomers, and to construct maps showing how dark matter distributes throughout the universe. However, note that this is not an effect of light Bending under its own force. Instead it represents an effect where photons travel along geodesic paths defined by Curvature in spacetime produced by nearby mass distributions.

Why do we never notice light being bent around everyday objects like walls and cars?

We do not see light being bent around everyday objects like walls and cars for reasons having nothing to do with how hard scientists want to measure it. The main reason is that everyday objects are vastly larger than anything in terms of wavelength measured at scale for visible light. For diffraction effects to be measurable (that is for the beam to spread out noticeably), an object or opening must be comparable in size to wavelength of visible light.

Also, even though scattered and diffracted rays exist all over the edges of everyday objects, our eyes are not sensitive enough to detect them. What we observe is mainly reflected or directly transmitted light that travels almost entirely in straight lines to our retinae.

In summary, although visible light travels in straight lines in a homogeneous medium (a vacuum or air), several mechanisms exist whereby light can be directed along paths that deviate from a straight course: diffraction (as above), total internal reflection (as above), metamaterials (as above), and gravitational lensing (as above).