The world of physics and photography is affected by a phenomenon of light known as diffraction . Many professional camera lenses are designed to provide excellent sharpness. However, even with very high quality, they cannot escape this phenomenon of light.
In this article we are going to tell you what is the diffraction of light and what are its characteristics and importance.
What is diffraction of light
When light waves pass through small openings and around obstacles or sharp edges, a phenomenon called light diffraction occurs. If an opaque object is placed between a point light source and a screen, the boundary between the shaded and illuminated regions on the screen will not be clearly defined. You can observe small amounts of light refracting from some of the shaded and illuminated regions, scattering towards the darker areas.
Light diffraction is a phenomenon that occurs when light waves pass through a narrow opening. When this happens, the light waves spread out and no longer travel in a beam. Whenever we talk about a point of light, we need to understand what a beam of light is. This beam is simply a stream of light passing through the air. In this case, when it passes through an opening, the light waves spread out, similar to how car headlights work at night, because the opening itself acts as the new light source.
Diffraction of light is used in cameras to force light through a very small hole. This is used to select the amount of light that we will use to take the photograph.
Key features
Light diffraction prevents light from concentrating at a precise point. This phenomenon causes it to disperse, forming what is known as an Airy disk. This disk is simply a representation of the deformation of the light beam and the waves projected onto a plane. In the case of photography, the plane is the camera's sensor.
The Airy disk is what photographers strive for to achieve balance. The goal is to capture an image with a shallow depth of field so that everything appears sharp. Thanks to the phenomenon of light diffraction, the camera's aperture can be closed to focus more efficiently in a photograph. However, there comes a point where closing the aperture results in a general loss of sharpness. Therefore, understanding how light diffraction works is crucial for optimizing photographs. To further explore these phenomena, you can also consult the article on iridescent clouds and the colors within them.
This phenomenon is also used in commercials to be able to generate visualizations that draw attention to the naked eye. The term diffraction comes from the Latin diffractus, which means has broken. It occurs mainly because a sling is able to go around an obstacle in its propagation, moving away from the behavior of the rectilinear rays. It must be borne in mind that the main effects of light diffraction are regularly small.
The phenomenon of distraction can be observed with the naked eye by holding two fingers about ten centimeters from your eye, creating a very small space between them. This is where you can see a series of dark and bright lines. These lines are primarily caused by what is known as constructive and destructive interference of light . This interference passes around the fingers, producing this effect.
Diffraction of light and Huygens principle
The reason for what happens with interference is not entirely obvious. The scientist Christiaan Huygens offered an explanation for this phenomenon. The explanation is based on electromagnetic radiation and its dynamics. When light leaves the source from which it is emitted, it expands as it travels. Its expansion occurs in a straight line, as if it were covering the surface of a continuously expanding sphere. The entire area of ​​expansion of the light increases proportionally to the square of the distance the radiation travels.
We consider that electromagnetic energy can propagate from a point source in plane waves. In this case, the inverse square law applies not only to the energy source but also to any point on a plane wave. Therefore, we can say that the waves are considered to be continuously created from every point in the plane and propagated in all directions. If we reduce the area from which the light is emitted, the surface area through which the light beam travels will also be reduced.
This Huygens principle was published more than 300 years ago and a new mechanism is proposed to know the propagation of light as we know it today. At this time it was considered that light traveled as waves in a kind of fictitious matter called ether and is supposed to fill the entire space. Each particle of ether that vibrates was seen as the origin of new waves. The spherical waves belonging to the initial light diffraction originate from a point source and are partially obscured by an infinite screen S.
The motion of light waves is defined by a speed within the cone bounded by the aperture of the screen. The aperture is known as the surface through which light can emerge. This principle is used to establish the laws of reflection and refraction for plane waves. Huygens' principle is relevant to optical geometry and is valid for extremely small wavelengths. However, it cannot be used to explain all phenomena related to light waves. For example, it does not explain the deviation of light rays in a straight line when they pass through the edge of an object or through small openings.
I hope that with this information you can learn more about the diffraction of light.