Wednesday, January 25, 2023

# What Is Ordinary Light In Physics

## What Is Ordinary Light

Comparison between Laser light and ordinary light

An ordinary light is the type of electromagnetic radiation having many wavelengths and is incoherent light. As the ordinary light is a mixture of different wavelengths, thus it is a polychromatic light.

The ordinary light is divergent, which means it can travel in all the directions randomly. The ordinary light does not have relation between the phases of its photons. For this reason, it is also an incoherent light.

The common practical examples of ordinary light are sunlight, light produced by different types of artificial lamps like incandescent lamp, tungsten filament lamp, fluorescent lamp, etc.

## Transverse Waves And Longitudinal Waves

Transverse waves are waves, in which the movement of the particles in the wave is perpendicular to the direction of motion of the wave.

Example: ripples in water when you throw a stone.

Longitudinal waves are formed when the particles of the medium travel in the direction of motion of the waves.

Example: the motion of sound waves through the air.

## What Is Plane Polarized Light

Plane polarized light is a type of EMR having its vibrations occurring within them in a single plane. We can make a light polarized by the process of polarization. It is a property of transverse waves that are specifically the geometrical orientation of the oscillations. Usually, a transverse wave has the direction of the oscillation perpendicular to the direction of motion of the wave. E.g. guitar string. In a guitar string, the vibration direction can vary according to the plucking of the string the direction can be vertical, horizontal, or other angles perpendicular to the string. Furthermore, the transverse waves that can undergo polarization include electromagnetic waves , gravitational waves, and transverse sound waves in solids.

Most of the sources of light are incoherent or unpolarized because there is a random mixture of waves with different spatial characteristics, frequencies, phases, and polarization states. It is easy to consider light or other EMR waves as a plane wave for understanding the polarization of EMR waves.

Figure 01: Vertically Polarized Light Wave

The methods we can use to plane polarize the light include polarization by transmission, polarization by reflection, polarization by scattering, and polarization by refraction.

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## Then Why Is The Laser Light Different From Ordinary Light

Because laser light is:

• Monochromatic – It contains only one specific wavelength and hence one color.
• Coherent – The motion of all photons is coordinated.
• Directional – The laser beam is very narrow, concentrated and therefore, it is a high intensity source.

Laser is an artificial source of light radiation that emits a coherent beam of photons, as the source is stable in frequency, wavelength, and power. Unlike the light emitted by common sources, such as light bulbs, laser light is mostly monochromatic, i.e. only one specific wavelength .

Gentec-EO’s high-accuracy laser beam measurement instruments help engineers, scientists and technicians in all sorts of laser applications from the factory to the hospital, laboratory and research center. Learn about our solutions for these measurement types:

When we talk about highly monochromatic lasers, we consider that the beam linewidth is very narrow. You can use these lasers especially for applications such as laser spectroscopy or coupling with optical fibers in fiber communications.

Take a look at other types of light sources: incoherent light sources . These sources produce radiation by spontaneous emission in all directions, with a spread of wavelengths and no interrelationships among individual photons. Spontaneous emission is a random process. On the other hand, lasers use stimulated emission, producing photons with identical properties .

## How Do Lasers Work

The principle of laser is what is called as stimulated emission of radiation. Einstein considered what would happen if an atom already in an excited state gets struck by a photon of the same energy as the previous photon, which sent the atom into the excited state.

He worked out that the atom would emit a photon of the same energy and go down to a lesser energy state in a process called stimulated emission. Now two photons are perfectly in sync- they have the same wavelength and same phase . These two photons can strike other excited atoms to produce more photons in the same wavelength and phase.

The light rays thus produced are monochromatic and coherent. In a laser device, this light is made to follow a path such that it becomes highly directional. Think of it like the battalion marching in a straight line in tight formation!

• Laser stands for Light Amplification by Stimulated Emission of Radiation.
• Production of coherent light in laser is done using stimulated emission.
• Laser beams are highly monochromatic, directional, and coherent.

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## Harry & Meghan Doc Reveals Whats Happening Behind Closed Doors: Trailer

Do Prince Harry and Duchess Meghan Markle want privacy or fame?

The co-hosts of The View discussed the timing of the estranged royals trailer uploaded on Thursday for their upcoming Netflix docuseries, Harry & Meghan.

Sunny Hostin said she didnt believe that the estranged royals had the power to decide that the trailer coincidently released when Harrys brother, Prince William, and his wife, Kate Middleton, started their US tour would come out while their in-laws were in the states.

But many of the ladies agreed that the timing was smart marketing.

However, the trailer release is believed to be a coordinated campaign to disrupt the prince and princess of Wales big stateside trip.

The one thing Im a little struck by, though, is, like, they already told their story, Alyssa Farah Griffin said. At the end of it, says, like, When the stakes are so high, you have to tell your story. You sat down with Oprah we all watched it. Ill probably binge-watch this when it comes out. But I kind of feel like theyre perpetuating putting themselves in the public eye when that was what they were trying to avoid.

Sara Haines agreed, saying that its hard to reconcile the desire for privacy with willingly releasing a documentary about their time in the royal family.

I gotta tell you something: If what they want is privacy and to get away from the royal family, they got a hell of a way of doing it, Ana Navarro added.

## What Is Polarized Light

Polarization of light includes the polarised light commonly produces most of the physical processes that follow the deviation of photon beams that include absorption with refraction, diffraction along with refractive polarisation and mechanism that carry off the basics of an extract of polarisation it also includes the double refraction of photolytic waves.

The light thats reflected from the flat surface of a dielectric material is usually partially polarized, with the electrical vectors of the reflected light vibrating during a plane thats parallel to the surface of the fabric. The common samples of facultative unit vectors are interrogated here and taken in granted by the scientists. In these examples, the maximum portion takes and cope up with the vector concept and photolytic deviation.

The vector resolution has many inclinations which conclude towards the maximum plane of physics concept and these result in polarization of light i.e, the polarisation of photolytes. The optical properties of the insulating surface determine the precise amount of reflected light thats polarized. Mirrors arent good polarizers, although a good spectrum of transparent materials acts as excellent polarizers.

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## Laser Light Properties Are Used All Around Us

Specific properties of artificial light obtained by lasers are advantageous for transmitting data for hundreds of miles, up to terabits per second, by a convenient, single wavelength coherent source. Nowadays, you can transmit data with laser beams through free-space optics technology over moderate distances with many Gbit/s data rates.

The laser has also become an important research instrument and has found its application in many fields, such as the correction of vision, the sharpening of the astronomical image from space, testing the DNA molecule and in obtaining pure energy by laser fusion of atoms.

Since the discovery of the laser, more than 30 Nobel Prizes have been awarded in the field of natural sciences for scientific discoveries directly related to lasers. In 2018, Donna Strickland became the second woman to receive a Nobel Prize in physics, which she was awarded for her work on ultra-short and high-intensity laser pulses. Measuring the laser’s properties with precision and accuracy is key to such research, which is why Gentec-EO develops and manufactures high-accuracy laser power meters and laser energy meters.

## What Is Laser Light

Polarization of light

LASER stands for Light Amplification by Stimulated Emission of Radiation. A LASER light is a form of electromagnetic radiation having only one wavelength of electromagnetic wave and is coherent light. Therefore, LASER light is a type monochromatic light, i.e. single color light. The LASER light is produced by using the concept stimulated emission, given by Albert Einstein.

The LASER light have photons that are in phase, therefore it is a coherent light. The LASER light has several unique feature such as directionality monochromatic, coherent, and narrow range of frequency, etc.

The LASER light is used in several specialized applications like laser diode, laser beam welding, laser drilling, laser cooling, etc.

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## Basic Properties Of Light

• Light radiation travels at a speed of approximately 299 792 458 metres per second in a vacuum . This is referred to as the speed of light.

The speed of light is the same for all electromagnetic waves.

The wavelengths and frequencies of electromagnetic waves distinguish them from one another .

= f

c = speed of light =3108 in a vacuum = 300,000 km/s = 186,000 miles/s

• The electromagnetic spectrum is a continuous representation of all electromagnetic waves organized by frequency and wavelength. Visible light constitutes only a small portion of the electromagnetic spectrum.

• The intensity or brightness of light decreases as the square of the distance from the source increases .

• Ray Model of Light-

To predict the path that waves will take, they are frequently approximated as rays. The ray model of light assumes that light moves in a straight line in a vacuum or uniform medium. A ray is a straight line that depicts the path of a very narrow light beam. Ray diagrams are diagrams that show the path of light rays. Despite ignoring the wave nature of light, ray diagrams are useful in describing how light behaves at boundaries and are frequently used to locate the image formed by a mirror or a lens.

• The Behaviour of Light at a Boundary-

The Three Possible Results of Light Energy when it interacts with Matter/Substances:

## Ordinary And Extraordinary Polarization

The paper Entangled biphoton source – property and preparation says

A very interesting situation of type-II SPDC is for non-collinear phase matching. The signalidler pair are emitted from a SPDC crystal, for example BBO, cut in type-II phase matching, into two cones, one ordinary polarized, the other extraordinary polarized . Along the intersection, where the cones overlap, two pinholes numbered as 1 and 2 are used for defining the direction of the $k$ vectors of the signalidler pair. One may consider the polarization state of the signalidler pair as,$$|\psi\rangle = \frac}$$where $o_j$, $e_j$, $j = 1, 2$ are ordinary and extraordinary polarization, respectively.

What does it mean by “ordinary and extraordinary polarization”? I haven’t heard those terms before.

The simplest way of modeling light traveling through a medium is with “ray-optics” which is a method by which you model your beam of light as a series of light rays. Here’s a picture to give you an idea of what it looks like if you haven’t seen it before:

I work in an quantum information lab that uses such a crystal for SPDC inside a cavity. Depending on what type of crystal you use, you can go from having entangled light to squeezed light!

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## Summary Plane Polarized Light Vs Ordinary Light

Light is a type of electromagnetic radiation having a wavelength that is detectable by the human eye. We can polarize light using analytical techniques. The key difference between plane polarized light and ordinary light is that the plane-polarized light has its vibrations occurring within them in a single plane whereas the ordinary light has vibrations occurring within them at random angles without any plane.

##### Reference:

1. Polarization of Light Definition, Types, Methods, & Applications. , BYJUS, 15 Oct. 2020.

##### Image Courtesy:

1. Electromagnetic wave By P.wormer Own work via Commons Wikimedia

## Main Difference Ordinary Light Vs Laser Light

Both ordinary light and laser light are electromagnetic waves. Therefore, both travel with the velocity of light in vacuum. However, laser light has very important and unique properties that cannot be seen in nature. Ordinary light is divergent and incoherent whereas laser light is highly directional and coherent. Ordinary light is a mixture of electromagnetic waves having different wavelengths. Laser light, on the hand, is monochromatic. This is the maindifference between ordinary light and laser light. This article focuses on the differences between ordinary light and laser light.

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## Use For Light On Earth

Sunlight provides the energy that green plants use to create sugars mostly in the form of starches, which release energy into the living things that digest them. This process of provides virtually all the energy used by living things. Some species of animals generate their own light, a process called bioluminescence. For example, fireflies use light to locate mates and vampire squid use it to hide themselves from prey.

## What Is A Photon

The fundamental particle of light is both ordinary and full of surprises.

What physicists refer to as photons, other people might just call light. As quanta of light, photons are the smallest possible packets of electromagnetic energy. If you are reading this article on a screen or a page, streams of photons are carrying the images of the words to your eyes.

In science, photons are used for more than just illumination.

Theyre ubiquitous, says Richard Ruiz, a research associate at the Institute of Nuclear Physics in Krakow, Poland, and a theorist looking for new physics at the Large Hadron Collider. Photons are everywhere in particle physics, so you almost forget about them.

The photon has fueled centuries of discovery, and it remains an important tool today.

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## S Used In The Polarization Of Light

There are a few methods used in the polarization of light:

• Polarization by Transmission

Following are the applications of polarization:

• Polarization is used in sunglasses to reduce the glare.
• Polaroid filters are used in plastic industries for performing stress analysis tests.
• Three-dimensional movies are produced and shown with the help of polarization.
• Polarization is used for differentiating between transverse and longitudinal waves.
• Infrared spectroscopy uses polarization.
• It is used in seismology to study earthquakes.
• In Chemistry, the chirality of organic compounds is tested using polarization techniques.

## Classical Greece And Hellenism

16 – Class 12 – Physics – Wave Optics – Polarisation

In the fifth century BC, Empedocles postulated that everything was composed of four elements fire, air, earth and water. He believed that Aphrodite made the human eye out of the four elements and that she lit the fire in the eye which shone out from the eye making sight possible. If this were true, then one could see during the night just as well as during the day, so Empedocles postulated an interaction between rays from the eyes and rays from a source such as the sun.

In about 300 BC, Euclid wrote Optica, in which he studied the properties of light. Euclid postulated that light travelled in straight lines and he described the laws of reflection and studied them mathematically. He questioned that sight is the result of a beam from the eye, for he asks how one sees the stars immediately, if one closes one’s eyes, then opens them at night. If the beam from the eye travels infinitely fast this is not a problem.

In 55 BC, Lucretius, a Roman who carried on the ideas of earlier Greek atomists, wrote that “The light & heat of the sun these are composed of minute atoms which, when they are shoved off, lose no time in shooting right across the interspace of air in the direction imparted by the shove.” . Despite being similar to later particle theories, Lucretius’s views were not generally accepted. Ptolemy wrote about the refraction of light in his book Optics.

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## Coherent Light And Its Emission In Lasers

The coherent light produced by a laser differs from ordinary light in that it is made up of waves all of the same wavelength and all in phase ordinary light contains many different wavelengths and phase relations. Both the laser and the maser find theoretical basis for their operation in the quantum theory. Electromagnetic radiation is emitted or absorbed by the atoms or molecules of a substance only at certain characteristic frequencies. According to the quantum theory, the electromagnetic energy is transmitted in discrete amounts called quanta. A quantum of electromagnetic energy is called a . The energy carried by each photon is proportional to its frequency.

An atom or molecule of a substance usually does not emit energy it is then said to be in a low-energy or ground state. When an atom or molecule in the ground state absorbs a photon, it is raised to a higher energy state, and is said to be excited. The substance spontaneously returns to a lower energy state by emitting a photon with a frequency proportional to the energy difference between the excited state and the lower state. In the simplest case, the substance will return directly to the ground state, emitting a single photon with the same frequency as the absorbed photon.