Vision, Color and Electromagnetic Waves Chapter 22.1 and 22.2, 24

Light can reach your eyes in one of two ways: 1.Light can come directly from an object that produces its own light, such as a light bulb. 1.Light can come directly from an object that produces its own light, such as a light bulb. 2.Light can be reflected from objects that do not produce their own light, such as clothes. 2.Light can be reflected from objects that do not produce their own light, such as clothes.

Color is how we perceive the energy of light. White light is a combination of all of the colors of light or the rainbow. Ex. Sun and electric lights White light is a combination of all of the colors of light or the rainbow. Ex. Sun and electric lights All of the colors in the rainbow are light of different energies. All of the colors in the rainbow are light of different energies. - Red has the lowest energy. - Red has the lowest energy. - Violet has the highest energy. - Violet has the highest energy.

Red,Orange,Yellow,Green,Blue,Violet

White light continued Objects appear different colors because they absorb some colors and reflect others. Objects appear different colors because they absorb some colors and reflect others. Ex. an orange absorbs all colors of the light spectrum except orange (this it reflects) which is the color you see. Ex. an orange absorbs all colors of the light spectrum except orange (this it reflects) which is the color you see. Pigments work by subtracting colors from white light. Pigments work by subtracting colors from white light.

How We See Colors Additive (or RGB) Color Process - a process that creates color by adding proportions of red, green, and blue together. Additive (or RGB) Color Process - a process that creates color by adding proportions of red, green, and blue together. We perceive colors as percentages of 3 additive primary colors: red, green, & blue. We perceive colors as percentages of 3 additive primary colors: red, green, & blue.

Using Color Subtractive (or CMYK ) Color Process- A process that creates color by subtracting colors from white light using absorption. Subtractive (or CMYK ) Color Process- A process that creates color by subtracting colors from white light using absorption. We perceive colors as a combination of percentages of 3 subtractive primary colors: cyan, magenta, yellow. We perceive colors as a combination of percentages of 3 subtractive primary colors: cyan, magenta, yellow.

CMYK Color Process CMYK process is another name for the subtractive color process. CMYK process is another name for the subtractive color process. It stands for cyan, magenta, yellow, and black. It stands for cyan, magenta, yellow, and black. The CMYK color process is used for making all colors seen in reflected light, including printing inks and fabric dyes. Cyan, magenta, and yellow are combined in various proportions to make any color. The CMYK color process is used for making all colors seen in reflected light, including printing inks and fabric dyes. Cyan, magenta, and yellow are combined in various proportions to make any color.

The Human Eye Light enters your eye through the lens and lands on the retina (a membrane in back eye) Light enters your eye through the lens and lands on the retina (a membrane in back eye) On the surface of the retina are light-sensitive cells called photoreceptors. On the surface of the retina are light-sensitive cells called photoreceptors. When light hits a photoreceptor, the cell releases a chemical signal that travels along the optic nerve to the brain. When light hits a photoreceptor, the cell releases a chemical signal that travels along the optic nerve to the brain. The brain translates the signal into the perception of color. The brain translates the signal into the perception of color. Some photoreceptors respond only to low energy and others only to high energy. Some photoreceptors respond only to low energy and others only to high energy.

Two Types of Photoreceptors Cones respond to color and there are 3 types: Cones respond to color and there are 3 types: 1) responds to red light (lowest energy) 1) responds to red light (lowest energy) 2)responds to green light 2)responds to green light 3) responds to blue light (highest energy) 3) responds to blue light (highest energy) We see white light when all 3 cones are equally stimulated. We see white light when all 3 cones are equally stimulated. Rods respond only to difference in intensity. Rods respond only to difference in intensity. Rod cells detect black, white, and gray. Rod cells detect black, white, and gray.

Electromagnetic Spectrum The light that we can see with our eyes is just a small part of the full spectrum of light that occurs in nature. We call this the electromagnetic spectrum. Because light is a composite of interacting electric and magnetic force fields. The spectrum extends from low energy microwaves and infrared light to the visible light, and then to more energetic forms of light such as ultraviolet and x-rays.

Electromagnetic Waves Wavelengths of light come in a range of sizes. Wavelengths of light come in a range of sizes. Electromagnetic waves have both magnetic and electrical qualities. Electromagnetic waves have both magnetic and electrical qualities. They exchange energy back and forth. Each cycle of the electric part of the wave creates a magnetic wave as it changes and vice versa. They exchange energy back and forth. Each cycle of the electric part of the wave creates a magnetic wave as it changes and vice versa.

Properties of Electromagnetic waves Frequency Wavelength Amplitude Speed -same in a vacuum (3x10 8 m/sec) Carry energy in proportion to their frequency. Higher frequency=Higher energy High frequency of light (color)=High energy Invisible, with the exception of visible light As Frequency increases, wavelength decreases

Radio wave, an electromagnetic wave. If you switch electricity on and off in a wire, the oscillating electricity makes an electromagnetic wave. Oscillating electric current in a radio tower makes ripples of electricity and magnetism that spread out from the radio tower at the speed of light as electromagnetic waves (radio waves). Lowest frequency wave Used in wireless networking, TV, Radio and Radar

Microwaves and Infrared Waves Length- 30cm (12 in.) to 1mm Cell phones use these Microwave oven tune microwaves to the natural frequency of water. Microwaves transfer energy to water molecules in the food to heat food. Length- 1mm to 700 nano’s Infrared waves called radiant heat. Heat from the sun. Used in heat lamps and TV remote controls.

The Sun in three colors of UV light. Only active regions emit energetic UV light, so the colorful portions show the Sun’s hottest and most violent areas. The solar emission of visible light has been stable over the past five billion years.

X rays and Gamma Rays High frequency wave Length- 10nm to nm Used in medical and manufacturing X rays are absorbed by your bones to make an X ray film Dangerous to body if exposed long time Highest frequency Smallest wavelength Generated in nuclear reactions Highest energy Dangerous to body Used in medicine and research

Temperature and Light It turns out that all objects with a temperature above absolute zero radiate light. The amount and kind of light that is radiated depends upon the object's temperature. The higher the temperature, the more light is radiated, and the more energetic the light. That's why blacksmiths heating up a horseshoe first see it begin to glow red, and then white as it gets hotter.

Temperature and Light continued The Sun's surface, which has an avg. temperature of 10,000 degrees Fahrenheit (5810 degrees Kelvin), primarily radiates visible light. That's why we can see sunlight. The surface of the Earth has an avg. temperature of 60 degrees Fahrenheit (288 degrees Kelvin), so it radiates in the infrared part of the spectrum. We can't see the light the Earth radiates.

Greenhouse Gases: water (H2O), carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). The temperature of an object is determined by a balance between incoming and outgoing energy. For the Earth, the incoming energy is the absorbed light from the Sun, and the outgoing energy is the infrared light the Earth radiates out to space. “Greenhouse gases" have a very special property. They do not absorb the visible light from the sun, but they do absorb the infrared light radiated by the Earth's surface. Without an atmosphere with its Greenhouse Effect, that balance would lead to very cold temperatures - well below the freezing point of water.

This process is known as the Greenhouse Effect. If greenhouse gases were not in the atmosphere, all the infrared light radiated by the Earth would go back out to space, leaving the Earth too cold for life. But the greenhouse gas molecules absorb the infrared light, and then re-radiate some of it back to the Earth's surface. This makes the surface hotter so it radiates more light, thus establishing an equilibrium at a higher temperature.