In this article, we will learn about the Polarization of light, types of polarization, Polarization of Light properties, and others in detail.

The combination of electric and magnetic forces traveling across space is known as light. A light wave’s electric and magnetic vibrations are perpendicular to each other. The magnetic field travels in one direction and the electric field in the other, but they are always perpendicular. So we have an electric field in one plane, a magnetic field perpendicular to it, and a travel direction that is perpendicular to both. Electric and magnetic vibrations can happen in a variety of planes.

The majority of the light in the reflected ray is polarised parallel to the plane, with only a few exceptions. In contrast, most of the light in a refracted beam is unpolarized, with one or two polarised components. As a result, we can see that the reflected and refracted rays are both partly polarised.

Suppose if we fix the propagation of the wave in the x-direction then it can oscillate in either the y-direction, z-direction or in a combination of both directions. Thus wave has two polarization in each y-direction and z-direction. This polarization of light can be measured using any polarized light-sensitive medium, such as lenses, prisms, and others.

When light strikes a molecule or an atom, the light energy is absorbed and re-emitted in multiple directions. Polarization causes this scattering. Furthermore, the emitted light travels in many directions.

Multispectralandhyperspectralimaging

Each technology is able to sense (“see”) outside the range of normal human vision. The difference is the number of bands and the narrowness of the bands.

Polarization of light is like giving direction to the chaotic dance of light waves. Imagine light as a crowd of people moving together but facing all different directions; polarization is like getting them all to move in harmony, facing the same way. It’s a process that turns the jumbled mess of directions in unpolarized light into a neat, single direction in polarized light.

Polaroids are polarising materials made up of molecules that are oriented in a specific direction. A pass axis exists on every Polaroid. Only the pass axis will enable light to flow through. Both the horizontal and vertical pass axes can exist on a polaroid. The way light passes through it is determined by these. When the light that is not polarised travels through a polaroid, it becomes polarised.

Consider this example about a US project to inspect orange groves, looking for citrus blight disease, which used a Headwall Photonics’ Hyperspec® VNIR hyperspectral solution with an OEM camera mounted on a UAV.

Multispectralandhyperspectralremote sensing

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With multispectral detection, you would certainly be able to see differences between various elements, such as a tree plantation versus another crop.

Multispectralcamera

Polarized light, on the other hand, refers to light in which the electric field vectors vibrate in a specific plane or direction. In polarized light, the electric field oscillations occur in a well-defined direction, rather than randomly. The process of transforming unpolarized light into polarized light is called polarization. Polarization can occur through various methods, such as reflection, transmission, scattering, or filtering.

Hyperspectral imagery consists of many more bands (hundreds or thousands) that are much narrower (10-20nm), using an imaging spectrometer.

In Circular Polarization, the electric field of light has two linear components that are perpendicular to each other and have identical amplitudes, but the phase difference is π ⁄ 2. The electric field that occurs will propagate in a circular motion.

If the unpolarised light is incident on a particle, then we obtain dispersed light. Now when this polarized light passes through the atmosphere the molecule in the atmosphere dispersed the polarized light in all possible directions. And this is how light scattering causes polarization. The dispersed light is emitted in a direction that is perpendicular to the incident beam. Furthermore, dispersed light has complete polarization, but light travelling through molecules has partial polarization.

This happens naturally, like when sunlight bounces off a lake, or artificially with special materials called polaroids that act like gatekeepers, only letting light waves through if they’re moving in the right direction.

Hyperspectral vs multispectralcamera

The incident ray reflected and refracted ray may all be seen in the diagram below. Unpolarised light is visible on the incident beam. The unpolarized light is depicted in the diagram above. The dot denotes perpendicular directions, whereas the lines denote parallel directions.

Imagine flying over a property and looking down at fields of different colours and appearance. You might decide you know what is planted in each paddock, with accuracy dependent on how low you are flying.

The more detailed the spectral information recorded by a sensor, the more information that can be extracted from the spectral signatures.

Polarization of Light: If you were to leave your house on a hot, sunny day, you would undoubtedly wear sunglasses. This is because the light emitted by the sun is unpolarized light and the sunglasses we wear transform the unpolarized light. Polarized light is light in which the electric field vector of the light is in the same phase and is perpendicular to the propagation of the light wave. The process of converting unpolarized light into polarized light is called polarization.

The law says that the reflected ray is fully polarised at a specific angle of incidence. The angle between the reflected and refracted rays is also 90°. Total Angle = 90° if i = iB, that is when the angle of incidence equals Brewster’s Angle.

Brewster’s Law states that, for an unpolarized light of a known wavelength that is incident on a transparent surface, experiences maximum plan polarization at the angle of incidence then the tangent of the incidence angle is the refractive index of the substance for the given wavelength.

Polarized light and unpolarized light are two types of light that differ in the orientation of their electric field vibrations.

Hyperspectralimaging

Hyperspectral sensors have much more detailed signatures than multispectral sensors and thus provide the ability to detect more subtle differences in aquatic and terrestrial features.

Imagine we could safely view the world through the eyes of different creatures, enabling us to view infrared radiation, ultraviolet light and reflected electromagnetic energy*. Well, we can, with the use of multispectral and hyperspectral sensors.

RGBvs multispectral vs hyperspectral

Polarization is the process of converting non-polarized light into polarised light. The light in which particles vibrate in all various planes is known as unpolarised light.

Polarization is a phenomenon induced by the wave nature of electromagnetic radiation, according to physics. Sunlight is an example of an electromagnetic wave since it travels through the vacuum to reach the Earth. Because an electric field interacts with a magnetic field, these waves are known as electromagnetic waves.

We can observe that there is a plane of vibration parallel to the plane in the diagram below. There is also a vibration plane that is perpendicular to the plane. The first picture is one that is not polarised. The second picture is polarised, meaning it is perpendicular or parallel to the first. So let’s start with polaroids to understand polarization.

There is no doubt that hyperspectral imagery is the most advanced precision ag solution to transform our analysis and optimisation of production, risk management, use of resources and reducing disease.

hyperspectralvs.multispectralremote sensing ppt

Any wave vibrating up and down perpendicular to the propagation of the wave is termed the transverse wave. As we know that a wave travels in 3-Dimensions and in the three dimensions there are two waves that are perpendicular to the propagation of the wave.

Polarization of light refers to the phenomenon in which waves of light or electromagnetic radiation are restricted to vibrate in a single direction.

Citrus blight destroys the vitality of trees and can spread throughout the grove. One of the early signs of this disease is a byproduct secreted on the surface of the leaves. Inspection for this used to require a person climbing a ladder to inspect the top of each tree. More often, growers might not know of a problem until trees started dying.  With hyperspectral imaging, this can be seen 300-400 meters above the crops covering a large area quickly (mounted on UAVs), allowing quick action to eliminate the spread and minimise the destruction.

Multispectralandhyperspectralremote sensing PDF

With hyperspectral capabilities, you will see individual trees and plants, and even the subtle differences in the EMR emitted by disease and soil moisture levels etc.

In its 2017-2019 Strategic Plan, the NSW Department of Primary Industries’ first goal is Innovation in primary industries to improve resilience and boost productivity.

Example: A beam of light strikes the surface of a plate of glass with a refractive index of √3 at the polarising angle. What will be the ray’s angle of refraction?

In linear Polarization, the electric field of light is confined to a single plane along the direction of the propagation of light.

This isn’t just for show; it has practical uses, like reducing glare in sunglasses, analyzing chemicals, and even making 3D movies pop. It’s a fascinating aspect of light that shows just how complex and useful this everyday phenomenon can be.

The light wave in which the electric field vectors vibrate in all possible directions perpendicular to the direction of propagation of the light is called unpolarized light. That is unpolarized light electric field vibrated randomly in all possible planes. We can define unpolarized light as a combination of light waves with all possible orientations of the electric field vectors. Sources of light such as the Sun or Incandescent bulbs emit unpolarized light.

In Elliptical Polarization, the electric field of light propagates along an elliptical path. The two linear components do not have the same amplitude and phase difference in elliptical polarization.

“Polarized Light Oscillates at a single phase in a particular plane whereas ordinary light has no plane and it vibrates at random angles.”