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reflectance and personal spectra

Different wavelengths appear to us in different colors. As light falls onto an object, the surface of the object absorbs specific wavelengths of light. The light that is not absorbed, is reflected. The object must selectively absorb and reflect some part of the visible spectrum for us to interpret the color.

CCD arrays

Digital cameras replace the film with a CCD photon detector, a thin silicon wafer divided into a geometrically regular array of thousands or millions of light-sensitive regions that capture and store image information in the form of localized electrical charge that varies with incident light intensity. The variable electronic signal associated with each picture element (pixel) of the detector is read out very rapidly as an intensity value for the corresponding image location, and following digitization of the values, the image can be reconstructed and displayed on a computer monitor virtually instantaneously.

florescence and florescent light

Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. e.g. glow paint A fluorescent lamp or a fluorescent tube is a low pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor which produces short-wave ultraviolet light that then causes a phosphor coating on the inside of the lamp to glow. A fluorescent lamp converts electrical energy into useful light much more efficiently than incandescent lamps.

Not polarized

From the sun or a light bulb light travels in many different directions

HID

High-intensity discharge lamps (HID lamps) are a type of electrical gas-discharge lamp. The tube is filled with both gas and metal salts. The gas facilitates the arc's initial strike. Once the arc is started, it heats and evaporates the metal salts forming PLASMA, which greatly increases the intensity of light produced by the arc and reduces its power consumption.

newtons experiments

Isaac Newton (1642-1726) the first to understand the rainbow — he refracts white light with a prism, resolving it into its component colors: red, orange, yellow, green, blue and violet. and concluding that white light was actually a mixing of the colors of the visible spectrum and not its own individual color.

LEDs

Light Emitting Diodes are more effective and practical, long lasting, semiconductor diode, does not give out much heat, dimmable. when a voltage is applied to the diode the electrons turn into photons creating light .

Lazers

Light amplification by the stimulated emission of radiation. The laser was invented by Theodore Maiman in 1960. All of the light being shone is at one wavelength, therefore giving a focused beam of light (the quantum effect).

polarization and nature ( rainbows, the sky, water , colors)

Light coming to us directly from the sun is not polarized. It is the part of sunlight that is scattered by molecules in the air that is polarized. The greatest polarization is produced when the light is scattered by 90 degrees

LCD displays

Liquid Crystal Displays are made of 5 layers— light, vertical polarizing filter, liquid crystals, and a horizontal polarizing filter. The liquid crystals can orient polarized light in a particular direction. In order for light to escape the display the liquid crystals must rotate the polarization of light by 90'.If the polarized light does not rotate it will be blocked by another polarizing filter oriented in the opposite direction.

metamerism

M___________ occurs because each type of cone responds to the cumulative energy from a broad range of wavelengths, so that different combinations of light across all wavelengths can produce an equivalent receptor response and the same tristimulus values or color sensation. In color science, such sensations are numerically represented by color matching functions.

spectral colors

Newton divided the spectrum into seven named colors: red, orange, yellow, green, blue, indigo, and violet

Color Vision

Our eyes are able to see all of the colors of the visible spectrum because of the cones on our retina. There are three different cone receptors, all that have unique sizes, that allow us to perceive all of the colors in our visible spectrum. each cone is sensitive to a particular band of wavelengths. The green and red cones are mostly found inside the fovea. blue cones are found around the fovea and have the highest light sensitivity

applications of polarization

Polarized sunglasses reduce the intensity of glare by cutting down the horizontally polarized light. Polarized light is used in photo elastic stress analysis. 3-D glasses have circular polarizers, one lens rotates clockwise and the other counter clockwise

color circles

The c______ c______ show how the primary colors of light mix together to form the secondary colors and white

blackbody radiation and color objects

The glowing from temperature. Objects of different material can have similar brightness and color of glow. The measurement of temperature is measured by the Kelvin scale (0° K = -273° c). 1900 Max Planck — spectra depends on temperature. As temp. increases, brightness increases. As temp. increases, projects shorter wavelengths. Color of glow depends on temperature— red is hot, blue is hottest. Blackbody radiation gives out a continuous, uninterrupted spectra. [The spectrum of the Sun— 5777 K blackbody.]

S and P polarization & how it relates to reflection

The plane in which the ray travels after reflection or refraction is refered to as S or P polarization Light reflected with its electric field parallel to the plane of incidence is thus denoted s-polarized, while light whose electric field is perpendicular to the plane of incidence is called p-polarized

Brusters Angle

The special angle of incidence that produces a 90° angle between the reflected and refracted ray is called the B_________ angle, D

tristimulus values

Thomas Young discovered that the human eye contains only three color receptors, which means that all colors are reduced to three sensory quantities.

Wavelengths and color

Wavelengths and frequencies correspond to the color of light we see. high frequency wavelengths appear blue and low frequency wavelengths appear red

Types of Polarization

- Linear - Circular - Reflected

absorption and emmision

When an object starts out cold and becomes hot, it forces the electrons inside the object to change states of energy. In lower energy states, electrons are close to the nucleus. Hotter temperatures creates the need for higher energy states, forcing electrons to move away from nucleus. As electrons travel in different states of energy— emits different colored light. When an electron is traveling down— it emits color from the Emission Spectrum. When an electron is traveling up— it absorbs color from the Absorption Line.

incandescent lights and how they work

When electricity flows through the filament, the lamp gives off light and gets hot in the usual way. In an incandescent lamp, the filament is made of tungsten metal and surrounded by a nonreactive ("inert") gas such as argon. This gas prevents the tungsten from burning and allows the light bulb to last longer.

Reflected Polarization

When light bounces off of a surface it can become partially p__________. the surface the light reflects off of determines the direction of the light that will be reflected.

bohrs model

With his model, Bohr explained how electrons could jump from one orbit to another only by emitting or absorbing energy in fixed amounts. The energy of an electron depends on the size of the orbit and is lower for smaller orbits. Radiation can occur only when the electron jumps from one orbit to another. The atom will be completely stable in the state with the smallest orbit, since there is no orbit of lower energy into which the electron can jump.

How anti-reflection coatings work

a_____ r_________ c________ are made by using constructive and destructive interference, similar to sound-canceling headphones

Polarizing Filters How and When they work

A p__________ f_______ only allows light to pass through in one orientation. e.g. horizontally or vertically . It can be oriented in any direction and it can block out all light rays traveling in other orientations

Wavelength

distance in meters for a wave to go through one complete cycle from crest to crest

Linear Polarization

electromagnetic radiation that only travels along one axis

electric discharge

the release and transmission of electricity in an applied electric field creates light through a medium such as a gas.

atomic spectra

the spectrum of frequencies of electromagnetic radiation emitted or absorbed during transitions of electrons between energy levels within an atom. Each element has a characteristic spectrum by which it can be recognized.

velocity

v__________ = wavelength times frequency

Spectral Lines

As electrons travel in different states of energy, they emit different colored light. A s_________ line is a dark or bright line in an otherwise uniform spectrum, resulting from emission or absorption of light in a narrow frequency range. Spectral lines are often used to identify atoms and molecules and have unique characteristics that help us identify what type of material is emitting light. Spectral lines coming from the sun can identify different chemicals from the stroke of the spectral line. Spectral lines vary in depth because different chemicals will have different efficiencies of absorbing light.

color and energy

As wavelength decreases, frequency increases and, as E=hf, where h is planks constant ( 6.62607004 × 10-34 m2 kg / s) Waves with a short wavelength have the most energy. Because violet waves have the shortest wavelength of the visible light spectrum, they carry the most energy.

atomic spectra in astronomy

Astrologist use the atomic spectra to record the elements that can be found on other stars or planets. By recording the light that comes from another planet with a spectrometer a scientist can use the spectral lines to determine what gases are in the atmosphere.

birefringence

B_____________ is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light. A widely used birefringent material is calcite. Its birefringence is extremely large, with indices of refraction for the o- and e-rays of 1.6584 and 1.4864 respectively.

Flames

Carbon, hydrogen and oxygen— atoms of a flame pyrolysis- when fume turns into gas chemiluminescence- blue flame oxidation- when oxygen forms with other atoms. when theres not enough oxygen= soot — makes yellow flame. Soot drinks in the light and energy and in response... it glows— incandescence yellow part- blackbody radiation of carbon soot blue part- line spectra of carbon, hydrogen and oxygen reacting together

cds and dvds

Cds and DVDs use lasers to recover data. The cd has microscopic holes and when the laser beam strikes "land", the beam is reflected onto a photoelectric cell. When it strikes a "ridge", the photocell will receive only a weak reflection. Thus the photoelectrical cell receives series of light pulses corresponding to the ridges and lands in the disc. These light pulses are the foundation of binary 'digital' data.

Circular Polarization

Circularly polarized light consists of two perpendicular electromagnetic waves of equal amplitude and 90° difference in phase. Circular polarization may be referred to as clockwise or counter-clockwise, depending on the direction in which the electric field vector rotates. (used in 3d glasses)

color temperature

Color temperatures over 5000 K are called cool colors (bluish white), while lower color temperatures (2700-3000 K) are called warm colors (yellowish white through red). the color measurment is based off of what color light a black body radiator would emit at specific temperatures in kelvin color temperature quantifies the blueness or redness of a light source produced by a blackbody of the same temp in K. the higher the # - the bluer it is and the lower the # - the redder it is. (CRI/color rendering index- 100- white balance)

types of spectra and their origins

Continuous Spectra Emission spectra- Hot gas wil begin to emit the lines in the emission spectra .Absorption Spectra- absorption lines refer to the tendency of cool atmospheric gas to absorb the same lines of light

barcode devices

As a red light shines onto the barcode, the sensor in the barcode scanner detects the reflected light from the illumination system (the red light bouncing off of white areas of the barcode) and generates an analog signal that is sent to the decoder. The decoder interprets that signal and coverts it into text.

photocopiers- the relation between light and electrons

1 the document is scanned and all of the black areas are recorded by a computer. 2 The computer then negatively charges the areas of the drum that need ink. 3 Positively charged toner then sticks to the negatively charged areas of the drum. 4 A sheet of paper is given a strong negative electrical charge. 5 The drum with ink rolls onto the paper and the positively charged toner sticks to the negatively charged paper. 6. The inked paper passes through two hot roller to fuse the toner particles permanently onto the paper.

Auroras

A_________ (also known as northern lights) occur in the northern and southern parts of the globe. Lights in the sky occur from particles (hot protons and electrons) from the sun (solar wind) that are trapped by the Earth's magnetic field and interact with the air, causing atmosphere to glow.

primary and complementary colors

Red, green, and blue are the p________ colors of light—they can be combined in different proportions to make all other colors. For example, red light and green light added together are seen as yellow light. which is a c__________ color along with cyan- a mixture of blue and green light and magenta- a mixture of red and blue light. This additive color system is used by light sources, such as televisions and computer monitors, to create a wide range of colors

rods and cones and where they're placed in the eye

Rods detect light levels and Cones detect color (for humans- red, green, blue) Cones are one type of photoreceptor, the tiny cells in the retina that respond to light. Most of us have 6 to 7 million cones. Red and green cones are inside the fovea, blue is around fovea.

types of light

Sun Incandescent Fluorescent LED

Frequency

The amount of wave crests that occur in one second Measured in hertz ( Hz) f=1/s Hz