Electromagnetic Wave Propagation - Electromagnetic waves can be generated by a variety of methods, such as a discharging spark or by an oscillating molecular dipole. Visible light is a commonly studied form of electromagnetic radiation, and exhibits oscillating electric and magnetic fields whose amplitudes and directions are represented by vectors that undulate in phase as sinusoidal waves in two mutually perpendicular (orthogonal) planes. This tutorial explores propagation of a virtual electromagnetic wave and considers the orientation of the magnetic and electric field vectors.

Most objects do not make their own light, they are illuminated by the sun or another source and we see them as a result of the sunlight reflected of them. If you go into a cave, you cannot see. Everything looks black because there is no sunlight.

I think you have a fundamental misapprehension of the way light interacts with an object. Most objects do not reflect light. They absorb light and re-emit it. When you see regular objects like a house or tree, you are not seeing reflected light. You are seeing light which is emitted by the object. The reason why objects have color is because the objects only emit light in certain frequencies. For example, the leaf of a tree absorbs all the red and blue light and re-emits light in the green part of the spectrum. At the atomic level what happens is that the light hits atoms of the object and the electrons of the atoms are momentarily excited. The electrons then return to their normal state and emit new photons in the process. The photons that are emitted are DIFFERENT photons than the ones that came in originally.

polarization极化

Sunlight and almost every other form of natural and artificial illumination produces light waves whose electric field vectors vibrate in all planes that are perpendicular with respect to the direction of propagation. If the electric field vectors are restricted to a single plane by filtration of the beam with specialized materials, then the light is referred to as plane or linearly polarized with respect to the direction of propagation, and all waves vibrating in a single plane are termed plane parallel or plane-polarized.

Introduction to Polarized Light - The human eye lacks the ability to distinguish between randomly oriented and polarized light, and plane-polarized light can only be detected through an intensity or color effect, for example, by reduced glare when wearing polarized sun glasses. In effect, humans cannot differentiate between the high contrast real images observed in a polarized light microscope and identical images of the same specimens captured digitally (or on film), and then projected onto a screen with light that is not polarized. The first clues to the existence of polarized light surfaced around 1669 when Erasmus Bartholin discovered that crystals of the mineral Iceland spar (more commonly referred to as calcite) produce a double image when objects are viewed through the crystals in transmitted light. During his experiments, Bartholin also observed a quite unusual phenomenon. When the calcite crystals are rotated about their axis, one of the images moves in a circle around the other, providing strong evidence that the crystals are somehow splitting the light into two different beams.

This is a question thats been bothering me a while. I don't even know if it makes sense or not (like if it is a physics question or becoming a philosophical one). But here it goes. The crux of my question basically is that we all know that we can't see light (like in its photon or electromagnetic wave form) directly when it is traveling past us. However, we also know that the way we see objects is by light reflecting off them. This then means that we are "seeing" the light reflecting from the object which then sends the signal to our brain saying that we are seeing a particular object. We know that both light traveling past us and light reflected from objects are made of photons (so they are the same kind)? So then my question is that what is happening to the photon of a light after it is reflected from the objects, that causes us to see it or the object, but on the other hand we can't see light as it is directly traveling past us.

Electric polarization

Edwin Herbert Land (1909-1991) - The founder of the Polaroid Corporation, Edwin Herbert Land was an American inventor and researcher who dedicated his entire adult life to the study of polarized light, photography and color vision. Perhaps Land's most famous contribution to science, however, was his development of instant photography. The invention was inspired by his three-year old daughter when she asked him why she could not instantly see a picture he had just taken of her on vacation. The one-step dry photographic process took Land three years to perfect, but his success was phenomenal.

Polarization of Light (3-D Version) - When non-polarized white light encounters a linear polarizer that is oriented with the transmission azimuth positioned vertically to the incident beam, only those waves having vertical electric field vectors will pass through. Polarized light exiting the first polarizer can be subsequently blocked by a second polarizer if the transmission axis is oriented horizontally with respect to the electric field vector of the polarized light waves. The concept of using two polarizers oriented at right angles with respect to each other is commonly termed crossed polarization and is fundamental to the concept of polarized light microscopy. This tutorial explores the effects of two polarizers having adjustable transmission axes on an incident beam of white light, and enables the visitor to translate the optical train in three dimensions.

Only the photons entering your eye enable you to see. Photons travel in straight lines, so you cannot see around corners. Your eye is tiny compared to the room you are in, so most of the photons bouncing off the objects around you go in other directions. Some of them may enter your friend's eye if they are with you.

Matthew J. Parry-Hill, Robert T. Sutter, Thomas J. Fellers, and Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.

Henri Hureau de Sénarmont (1808-1862) - Sénarmont was a professor of mineralogy and director of studies at the École des Mines in Paris, especially distinguished for his research on polarization and his studies on the artificial formation of minerals. He also contributed to the Geological Survey of France by preparing geological maps and essays. Perhaps the most significant contribution made by de Sénarmont to optics was the polarized light retardation compensator bearing his name, which is still widely utilized today.

Polarized Light Microscopy Web Resources - Although much neglected and undervalued as an investigative tool, polarized light microscopy provides all the benefits of brightfield microscopy and yet offers a wealth of information, which is simply not available with any other optical microscopy technique. This section is a compendium of web resources focused on all aspects of polarized light microscopy, optical crystallography, and related techniques.

Polarized Light Microscopy -The polarized light microscope is designed to observe and photograph specimens that are visible primarily due to their optically anisotropic character. In order to accomplish this task, the microscope must be equipped with both a polarizer, positioned in the light path somewhere before the specimen, and an analyzer (a second polarizer), placed in the optical pathway between the objective rear aperture and the observation tubes or camera port. Image contrast arises from the interaction of plane-polarized light with a birefringent (or doubly-refracting) specimen to produce two individual wave components that are each polarized in mutually perpendicular planes. The velocities of these components are different and vary with the propagation direction through the specimen. After exiting the specimen, the light components become out of phase, but are recombined with constructive and destructive interference when they pass through the analyzer. Polarized light is a contrast-enhancing technique that improves the quality of the image obtained with birefringent materials when compared to other techniques such as darkfield and brightfield illumination, differential interference contrast, phase contrast, Hoffman modulation contrast, and fluorescence.

Sir David Brewster (1781-1868) - Sir David Brewster was a Scottish physicist who invented the kaleidoscope, made major improvements to the stereoscope, and discovered the polarization phenomenon of light reflected at specific angles. In his studies on polarized light, Brewster discovered that when light strikes a reflective surface at a certain angle (now known as Brewster's Angle), the light reflected from that surface is plane-polarized. He elucidated a simple relationship between the incident angle of the light beam and the refractive index of the reflecting material.

Circularlypolarized light

Double Refraction (Birefringence) in Iceland Spar - The first clues to the existence of polarized light surfaced around 1669 when Erasmus Bartholin discovered that crystals of the mineral Iceland spar (more commonly referred to as calcite) produce a double image when objects are viewed through the crystals in transmitted light. This interactive tutorial simulates viewing of a ball-point pen and a line of text through a crystal of Iceland spar, producing a double image.

Unpolarizedlight

Shinya Inoué (1921-Present) - Shinya Inoué is a microscopist, cell biologist, and educator who has been described as the grandfather of modern light microscopy. The pioneering microscopist heavily influenced the study of cell dynamics during the 1980s through his developments in video-enhanced contrast microscopy (VEC), which is a modification of the traditional form of differential interference contrast (DIC) microscopy. Inoué also made significant contributions to the investigation of biological systems with polarized light microscopy. His seminal work, "Video Microscopy," was published in 1986, and a second revised and updated edition, co-authored with Kenneth Spring, followed in 1997. The book is a cornerstone of microscopical knowledge and is highly regarded throughout the scientific community.

To see something light must enter the eye and the rods (and cones) must be stimulated sufficiently for the signals to be produced for processing by the brain.

Now we all know that photons don't emit photons, so no photons coming from the photon will reach your retina, which is why we can't form an image of a photon in our visual cortex. It just passes by without sending photons to your retina.

Polarization

p-polarizedlight

You can see the light which enters in your eye and is absorbed by your retina. So you cannot see the light passing by because it is not going towards your eye. If it meets an object, however, light will be reflected or scattered and part of it will go towards your eye. You will then see the light coming from the object.

Polarized Light Waveforms - The ordinary and extraordinary light waves generated when a beam of light traverses a birefringent crystal have plane-polarized electric vectors that are mutually perpendicular to each other. In addition, due to differences in electronic interaction that each component experiences during its journey through the crystal, there is usually a phase shift that occurs between the two waves. This interactive tutorial explores the generation of linear, elliptical, and circularly polarized light by a pair of orthogonal light waves (as a function of the relative phase shift between the waves) when the electric field vectors are added together.

So to see an object like a photon passing you, the photon has to emit itself photons in all directions (or reflect photons shined on it, which is ruled out by QM, because it alters the state of the photon you want to "see", and because the frequencies of photons and the photons you shine on the photons must have frequencies which lie outside the part of the photon frequency spectrum in which the photons are "visible"), a part of which is reaching your retina after which an image of the photon is created in your visual cortex.

Polarized Light Virtual Microscopes - When a birefringent material is placed between crossed polarizers in an optical microscope, light incident upon the material is split into two component beams whose amplitude and intensity vary depending upon the orientation angle between the polarizer and permitted vibration directions of the material. Use this link to explore our tutorials on polarized light microscopy.

Reflected light usually is whitish yellow because that is the color of the sun. Reflected light is what we call "glare". When you see the glare of the sun off the water of a lake that is reflected light. Reflected light bounces off of materials that for whatever reason cannot absorb the light. Reflected light is always whatever color it was originally.

Polarized Light Literature References - A number of high-quality books and review articles on polarized light microscopy have been published by leading researchers in the field. This section contains periodical location information about these articles, as well as providing a listing of selected original research reports and books describing the classical techniques of optical crystallography and polarized light microscopy.

Max Berek (1886-1949) - Max Berek was a German physicist and mathematician, associated with the firm of E. Leitz, who designed a wide spectrum of optical instruments, in particular for polarized light microscopy and several innovative camera lenses. Professor Berek is credited as the inventor of the Leica camera lens system at their Wetzlar factory.

The reflected light is moving toward/into your eye, while the light just passing by you isn't. You can see light that's not "reflected", like the light emitted by a light bulb, there's nothing special about reflected light. All that's needed to see light is the light actually hitting your retina.

polarization中文

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Polarization of Light - When light travels through a linear polarizing material, a selected vibration plane is passed by the polarizer, while electric field vectors vibrating in all other orientations are blocked. Linearly polarized light transmitted through a polarizer can be either passed or absorbed by a second polarizer, depending upon the electric vector transmission azimuth orientation of the second polarizing material. This tutorial explores the effect of rotating two polarizers on an incident beam of white light.

If you want a more technical description description of the interaction of light with matter read this paper from the Yale astronomy department or better yet the lectures of Feynman on the interaction of light with matter.

Brewster's Angle - Light that is reflected from the flat surface of a dielectric (or insulating) material is often partially polarized, with the electric vectors of the reflected light vibrating in a plane that is parallel to the surface of the material. Common examples of surfaces that reflect polarized light are undisturbed water, glass, sheet plastics, and highways. In these instances, light waves that have the electric field vectors parallel to the surface are reflected to a greater degree than those with different orientations. This tutorial demonstrates the polarization effect on light reflected at a specific angle (the Brewster angle) from a transparent medium.

Linear polarization

Douglas B. Murphy - Department of Cell Biology and Microscope Facility, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, 107 WBSB, Baltimore, Maryland 21205.

Seeing something means detecting the shape, size, location and what wavelength of light it reflects (colour), without touching it. We only detect light that strikes our retina. Therefore we feel light, we don't see light. Feeling light is part of the process we call seeing.

I would add that if you put your eye before the object, into the light illuminating it, you will see the incoming light just as well.

In short, even though you might read that in "diffuse reflection" the light "bounces" off of the materials atoms, this is not true. It is actually absorped and re-emitted at the same wavelength. This can happen by two mechanisms: Thomson Scattering or Resonant Scattering. Either way, all the photons are absorbed and partially re-admitted (unless the object is black and they are all absorbed.

You cannot see a beam of light from a low powered laser which is not directed into your eye if the air through which the light is travelling is devoid of dust. Adding dust to the air and you can see the trajectory of the laser beam because of the light being reflected/scattered from the dust and enters your eye.

So - what happens to the photons reflected off the objects around you that don't enter your eye? Well, if you are indoors, most of them will be absorbed by other objects and their energy will be dissipated as heat. If you are outside, quite a lot of them will be angled up towards the sky and out into space. Eventually, they may hit a planet or a nebula and be absorbed. It doesn't really matter.

Well done. You grasp a concept which many can't. The simplest explanation is that we don't see light, we feel light. By light I mean photons, not brightness. We see brightness because it is a visual sensation created by our brain. When our retina detects a photon it sends a message to the brain and the brain interprets this message as an image. Everything you see is created by the brain. A 3 dimensional visual representation of our surroundings.

Nicol Prisms - Several versions of prism-based polarizing devices were once widely available, and these were usually named after their designers. The most common polarizing prism (illustrated in the tutorial window) was named after William Nicol, who first cleaved and cemented together two crystals of Iceland spar with Canada balsam in 1829. Nicol prisms were first used to measure the polarization angle of birefringent compounds, leading to new developments in the understanding of interaction between polarized light and crystalline substances. This interactive tutorial explores the generation of orthogonal or mutually perpendicular (ordinary and extraordinary) waves as the result of light transmission through a Nicol prism.

Seeing an object means that the photons coming from the object (either by reflecting photons from the object or by emitting photons from the object itself) reach your retina which sends signals to your visual cortex, where an image of the object is created.You don't see the photons but the object.