Dispersion | Optical phenomena

Light dispersion

If a beam of white light through a glass prism separates the rainbow of seven colors. Red, orange, yellow, green, blue, indigo and violet are the seven colors that Newton listed first. Are the colors that make up white light.

A monochromatic light, which we have spoken in the Laser post is one that consists of a single color, with a single frequency.

The polychromatic light consists of a mixture of colors with different frequencies. Thus, each frequency is refracted at a different angle, each frequency radiation follows a different route and seven colors appear separated.

According to Newton, the angle of refraction is greater the higher the frequency of the light. It is because of the dispersion of light, for example, form the rainbow in the sky. In a very simplified way, just replace the prism of our poster for a drop of water ... and imagine!

Curiosity
The sky is blue due to scattering of sunlight by the atmosphere which causes, from all directions, comes in bluish light. The reduced dimensions of the air molecules cause the shorter wavelengths, such as blue and violet, suffer major deviations white when sunlight shines on them. Therefore, the more "spread" color is blue, prevailing over the other and giving the sky its characteristic color.

Photograph of our own. Lavadores Beach, Vila Nova de Gaia.

At dawn and dusk because of the position of the sun, the light reaches us more inclined and must traverse a greater distance through the atmosphere, as we saw in the previous article. This causes the blue is more absorbed and the light that reaches our eyes pass to have a more reddish hue.

Refraction | Optical phenomena

When light passes from one transparent medium to another, the direction of light rays changes. Refraction occurs.
Depending on the speed of light, which depends on the medium through which light propagates, the change direction of the light rays can be more pronounced. The speed of light is higher in air than in water or glass, for example.
Like the reflection, there are also laws of refraction.

When light passes from a medium with greater speed to a medium with lower speed, the light rays are
close to the normal direction (N).
In turn, when light passes from a medium with a medium-low speed for higher speed, the light rays deviate from the normal direction (N).
Refraction never happens in isolation. In fact, when the incident ray hits the surface that separates the two media, part of it is reflected and some is absorbed. Thus, the intensity of refracted light waves is always lower than the intensity of the incident waves.


Curiosity
During sunset, the sun emits light that passes through a number of different layers of the atmosphere
and suffers refractions. The light arriving at the bottom of Sol is less than the deflected light from the top. That's why the sun appears flat when it's too close to the horizon. In fact, the sun is already below the horizon, but still see it because their light is bent as Einstein has predicted in his theory of general relativity, and that was proven in reality, the solar eclipse of May 29, 1919.


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Mirrors | Optical phenomena

Being smooth, polished and good light reflective surfaces, mirrors can be of two types: flat or curved. Quickly discuss the first to justify an experience.

Flat mirrors

The images of flat mirrors are constructed using the laws of reflection, described in the previous article.
They are virtual because they can not be projected on a target.
They are right, because they do not appear inverted (upside down).
They are symmetrical, because the left and right are reversed.
They have the same size of the object.

Thus, reverse the writing mnemonic OBAFGKM (developed in article Star Digital Printing) so that this situation can be demonstrated experimentally, with the added value of our poster colors match the spectral class of stars.

The scheme is intended to only show the effect, so it does not comply with certain rules, in particular on the size of objects (real and virtual).

Reflection | Optical phenomena

LIGHT REFLECTION

When a ray of light hits a surface and part of "back to back", we say that was reflected.

It is called normal to line N, which is perpendicular to the surface at the point where the beam
focuses.
Flame incident angle is the angle that the incident beam makes with the normal (A).
Flame reflected angle is the angle that the reflected beam makes with the normal (B).

Reflection laws
The angle that the ray makes with the normal when it hits the surface, is equal to the angle it makes with the normal to be reflected.
The normal line, the incident ray and the reflected ray are all on the same plane.

The thought never happens in isolation. In fact, when the incident ray hits the surface that separates the two media, part of it is absorbed and other part may undergo refraction. Thus, the intensity of light reflected waves is always lower than the intensity of the incident waves.

The reflection of light is represented on the poster.

Note: The addressed topics refer to specular reflection, which occurs at very smooth surfaces. It also happens reflection on uneven surfaces (diffuse reflection), occurring, however, dispersion luz.Verifica It is still the total reflection phenomenon in optical fiber, covered in Powering the World.

LED | Light Emitting Diode

The light emitting diode, which is better known by the English acronym 'LED', has been revolutionary in lighting. Its applications are vast, such as microelectronics, signage, displays / panels; and even as invention associated with the Nobel Prize this year. http://goo.gl/DJODJj


The LED is a semiconductor diode that when receiving electricity emits visible light (electroluminescence). The emitted light is not monochromatic but its color mainly depends on the crystal and the impurity which it is placed.

The red LED of high efficiency, was produced in 1962 and their constitution there is a GaAsP compound, or consists of a Gallium Arsenide crystal (GaAs) with doping phosphorus (P).
The green LED of high efficiency, was produced in 1972 and their constitution there is AlGaP compound, or consists of a gallium phosphate crystal with aluminum.
The blue LED, broadband, was produced in 1994 and their constitution there is InGaN compound, or consists of a crystal gallium nitride (GaN) doped with indium (I).

The Wikipedia site presents us with a elaboradíssima page on this topic, which we recommend reading: http://goo.gl/GIFNh2

Powering the World | Optical Fiber

As can be seen in this representation of optical fiber, below the title: "TECHNOLOGY BASED ON LIGHT" will consider this technology and its connection with the world.

Social networking, phone calls low-cost video calls with family and friends. Three examples of many representatives of the internet, derived from the light and empowering communication between people and the rest of the world. The speed of the Internet has increased throughout history, substantially with the discovery of optical fiber. Then, and what is it?

The optical fiber is a transparent and very thin wire with a diameter of 0.5 mm, similar to a hair, which replaced the metal cables. This has cylindrical structure and is divided into two parts, core and coating, where the core is the central region and the shell is the region that surrounds the core on its outside.
The refractive index of the core material is more refractile (causes larger deviation of light) than the coating, such that a ray that enters at one end, with an angle greater than the critical angle, moves the core fiber undergoing total reflections on the walls until you reach the other end.
The fiber optic cables are advantageous compared to metal cables:
Abundant raw materials;
Greater information transmission capacity;
Does not suffer from electromagnetic wave interference;
As the wires are made of polymers, they do not corrode and will not rust as metallic wire;
Small size and weight.
The official website of the International Year of Light published an article dedicated to the importance of the link between light and communication! Just enter the following link:
http://goo.gl/80y0wn

Stars 'Fingerprints'

The temperatures of the stars can be classified using the Wien displacement law, which is in section formulas that relate the light and matter. The great diversity of observed stellar spectra gave rise to the classification of the stars in seven spectral classes:

OBAFGKM
Oh, Be A Fine Girl, Kiss Me!

Moreover, each class is divided into 10 subclasses designated spectral types: B2; B5; A0; A5, for example. Out of curiosity, the sun is a star that is contemplated in the G2 class.

Depending on the constitution of the atmosphere of stars, we can relate the spectra with the previous absorption temperatures and the respective spectral classes (with a predominant color).

Classe	Temperatura (kelvin)	Cor convencional	Cor aparente
O	≥ 33 000 K	azul	azul
B	10 000–33 000 K	azul-branco	azul-branco
A	7 500–10 000 K	branco	branco a azul-branco
F	6 000–7 500 K	amarelo-branco	branco
G	5 200–6 000 K	amarelo	amarelo-branco
K	3 700–5,200 K	laranja	amarelo-laranja
M	2 000–3 700 K	vermelho	laranja-vermelho

Daltonism | Past and future

In our poster in the location corresponding to the focus blue LED we decided to examine the condition of blindness which is directly related to the color and therefore with light.

The inability to distinguish colors has the medical designation dyschromatopsia. This change in vision is usually known for color blindness.

This designation is a tribute to the chemist John Dalton who described this for the first time. This scientist, who lived in the eighteenth century was a prestigious chemist who made discoveries and extensive range that being a carrier of this visual defect, described it perfectly.

There are three main colors: blue, green and red. On the one hand the junction of these three colors gives white, and on the other hand all the other colors or shades are the sum of these three colors.
It is understood that an error or defect in a cell type refers to one of three colors, resulting in a defect of this particular color, but also have consequences for the composition of all other composite colors and where the missing color can not cooperate.

As such, we also made reference to ColorAdd which is a national project and aims to represent all colors using only symbols.

We also decided to join two important technological advances in the field of technology related to color, building a bridge between the past and the future, creating a renewed version of Newton's disk-bases in the ColorAdd.

Light-energy relations | Formulas

In the focus from the green LED it is possible to find a set of formulas that establish various relations between light and energy.

First, we have to Wien's displacement law of the formula that relates the wavelength (where is located the maximum emission of electromagnetic radiation of black body) and the temperature.

Second, it can be find the Stefan-Boltzmann law for calculating the brightness of a particular body.

Subsequently, there is the presence of Planck's relationship which is used for quantifying the electromagnetic energy.

Finally, there is the famous law of mass-energy equivalence, Einstein, which relates the energy of a body with its mass and speed of light in vacuum.

Thus, this location in the poster possesses extensiva range of formulas that establish relationships between light (energy) and matter.

Laser | Light based technologies

In our poster, in the location of the red LED focus, the Laser was used as an illustration of a technology based on light and extremely important in everyday life.

There are predominantly 4 types of lasers, each with different features and utilities, they being the following:

Laser Type 1 - Use in readable (bar code), or CD's;
Laser Type 2 - Use on DVDs;
Laser Type 3 - Use in medical technology (LASIK);
Laser Type 4 - Military Use (Laser Weapons).


Laser plays a key role in diversa utilities and it presents very special characteristics such as the fact of being monochromatic, that is, having with a wavelength very well defined, and collimated, which means parallel propagation of light beams. The collimation process is represented on the poster along the collimator, which is by the prism.