LIGHT: What is it? - Home - Coosa High School

LIGHT: What is it? - Home - Coosa High School

2000 Microsoft Clip Gallery WAVES & LIGHT Waves carry energy from one place to another NATURE OF WAVES 2000 Microsoft Clip Gallery

Waves (Def.) A wave is a disturbance that transfers energy from one point to another. Medium Substance or region through which a wave is transmitted. Speed of Waves Depends on the properties of the medium.

Transverse Waves 2000 Microsoft Clip Gallery Light and Electromagnetic Compression or Longitudinal Waves Sound

Waves contd LIGHT: What Is It? 2000 Microsoft Clip Gallery Light Energy Atoms As atoms absorb energy, electrons jump out to a higher energy level. Electrons release light when falling down to the lower energy level. Photons - bundles/packets of energy

released when the electrons fall. Light: Stream of Photons 2000 Microsoft Clip Gallery Properties and Sources of Light Light travels almost unimaginably fast and far. Light carries energy and information. Light travels in straight lines. Light bounces and bends when it comes in contact with objects.

Light has color. Light has different intensities, it can be bright or dim. The speed of light The speed at which light travels through air is approximately 300 million meters per second. Light travels almost a million times faster than sound. Electromagnetic Spectrum 2000 Microsoft Clip Gallery

Electromagnetic Spectrum Visible Spectrum Light we can see Roy G. Biv Acronym for Red, Orange, Yellow, Green, Blue, Indigo, & Violet. Largest to Smallest Wavelength. Radio Waves

Invisible Spectrum Longest wavelength & lowest frequency. Also emitted by Stars and gases Dangers: Radio wave

sickness Cancers leukemia 2000 Microsoft Clip Gallery Modulating Radio Waves 2000 Microsoft Clip Gallery

AM Carries audio for T.V. Broadcasts Longer wavelength so can bend around hills FM Carries video for T.V. Broadcasts Infrared Rays Invisible Spectrum (Cont.) Light rays with longer wavelength than red light.

Our skin emits infrared rays Far infrared = hot ; Shorter infrared = cool Uses: Cooking, Medicine, T.V. remote controls, military thermal imaging, astronomy and weather forecasts, heat lamps for sports medicine Dangers Too much exposure = overheating

Infrared: Thermal Imaging Microwaves Basically high frequency radio waves Used in satellite communication and transmission, radar systems and microwave cooking/microwave oven travels in straight line without losing much of its energy

Dangers: Prolonged exposure causes cataracts Cell phones may cause Brain damage (tumors) satellite station speed-monitoring radar

Ultraviolet Rays Invisible spectrum (cont.). Humans cant see, but some insects can EM waves with frequencies slightly higher than visible light

USES: USES tanning beds, astronomy, food processing & hospitals to kill germs, attracts insects (kills them), detecting counterfeit money, whitening teeth, hardening dental fillings, black light, helps your body produce Vitamin D Ozone layer blocks most UV from getting to earth

DANGERS: DANGERS UV-B CHANGES DNA IN CELLS CANCER

SKIN AND EYE DAMAGE, SUNBURN X-RAYS Invisible Spectrum High frequency waves

An X-ray machine works by firing a beam of electrons at a "target". If we fire the electrons with enough energy, X-rays will be produced. Uses: Medicine Bones absorb x-rays; soft tissue does not., airport security, astronomy Lead absorbs X-rays

Dangers: Dangers Cancer, Cell damage esp. in first trimester for fetus AIRPORT X-RAY MACHINE GAMMA RAYS Invisible

spectrum (cont.) Highest frequency EM waves; Shortest wavelength. They come from outer space. Uses: cancer treatment, radioactive tracers, sterilize foods through irradiation.

Dangers: Kills all living cells Causes cancer Only lead or concrete will block

Visible light Seen by the human eye Uses: fiber optics, medical procedures, telecommunications, chemical spectral analysis and photosynthesis, endoscopy. Lasers for medical, industrial and surveying use. CD's and DVD's, Laser printers, Dangers: Dangers Too much light can

damage retina laser surgery Visible Light contd Process of transforming light, water and carbon dioxide into glucose and oxygen. LIGHT: Refraction of Light

Refraction Bending of light due to a change in speed. Index of Refraction Amount by which a material refracts light. Prisms Glass that bends light. Different frequencies are bent different amounts & light is broken out into different colors. Refraction (Cont.) Refraction contd Another example of

refraction of light is the twinkling of a star in the night sky As starlight travels from space into the Earths atmosphere, the rays are refracted. Since the atmosphere is constantly changing, the amount of refraction also changes.

Color of Light Transparent Objects: Light transmitted because of no scattering Color transmitted is color you see. All other colors are absorbed. Translucent: Light is scattered and transmitted some. Opaque: Light is either reflected or absorbed. Color of opaque objects is color it reflects.

2000 Microsoft Clip Gallery OPAQUE 16.2 Color and Vision When all the colors of the rainbow are combined, we do not see any particular color. We see light without any color. We call this combination of all the colors of light "white light". 16.2 Color and Vision

We can think of different colors of light like balls with different kinetic energies. Blue light has a higher energy than green light, like the balls that make it into the top window. Red light has the lowest energy, like the balls that can only make it to the lowest window.

How the human eye sees color The retina in the back of the eye contains photoreceptors. These receptors release chemical signals. Chemical signals travel to the brain along the optic nerve. optic nerve Photoreceptors in the eye

Cones respond to three colors: red, green and blue. Rods detect intensity of light: black, white, shades of gray. How we see colors Which chemical signal gets sent depends on how

much energy the light has. If the brain gets a signal from ONLY green cones, we see green. 16.2 How we see other colors The three color receptors in the eye allow us to see millions of different colors.

The additive primary colors are red, green, and blue. We dont see everything white because the strength of the signal matters. All the different shades of color we can see are made by changing the proportions of red, green, and blue. 16.2 How we see the color of

things When we see an object, the light that reaches our eyes can come from two different processes: 1. The light can be emitted directly from the object, like a light bulb or glow stick. 2. The light can come from somewhere else, like

the sun, and we see the objects by reflected light. 16.2 How we see the color of Colored fabrics andthings paints get color from a subtractive process. Chemicals, known as

pigments, in the dyes and paints absorb some colors and allow the color you actually see to be reflected. Magenta, yellow, and cyan are the three subtractive primary colors. 16.2 Why are plants green?

Plants absorb energy from light and convert it to chemical energy in the form of sugar (food for the plant). Chlorophyll is an important molecule that absorbs blue and red light. How You Seeagain

2000 Microsoft Clip Gallery Retina Lens refracts light to converge on the retina. Nerves transmit the image Rods Nerve cells in the retina. Very sensitive to light & dark Cones Nerve cells help to see color

Human Eye Diagram LIGHT & ITS USES 2000 Microsoft Clip Gallery Sources of Light 2000 Microsoft Clip Gallery Electric Light

The process of making light with heat is called incandescence. Incandescent bulbs generate light when electricity passes through a thin piece of metal wire called a filament. The filament heats up and gives off light. Electric Light The other common kind of electric light is the fluorescent bulb. Fluorescent bulbs

convert electricity directly to light without generating a lot of heat. Fluorescent bulbs use high-voltage electricity to energize atoms of gas that fill the bulb. Compact Fluorescent lights

Energy Efficient Designed to replace incandescent lights Must be disposed of properly DANGERS: Mercury poisoning Destroys neurons LIGHT & ITS USES - Neon Neon light neon gas

inside glass tubes Electrodes on each end bounce off electrons and make red light. Other gases make other colors. Krypton blue

and Argon - purple 2000 Microsoft Clip Gallery Light Emitting Diodes: LED

Tiny bulbs that fit on a circuit No filament Do not emit heat Illuminates by movement of electrons More costly, but VERY energy efficient Long life-span USES: digital clocks, traffic lights, TV, remote controls basically anywhere Light carries energy and power Light is a form of energy that travels.

The intensity of light is the amount of energy per second falling on a surface. Most light sources distribute their light equally in all directions, making a spherical pattern. Because light spreads out in a sphere, the intensity decreases the farther you get from the source. LIGHT & ITS USES - Reflection Reflection waves

Bouncing back of light LIGHT & ITS USES: Reflection Vocabulary Real Image Can be projected onto a screen because light actually passes through the point where the image appears Always inverted

LIGHT & ITS USES: Reflection Vocabulary Virtual Image Not Real because it cannot be projected Formed in locations where light does NOT reach Image only seems to be there! Light & Its Uses:

Mirrors Reflection Vocabulary Optical Axis Base line through the center of a mirror or lens Focal Point Point where reflected or refracted rays meet & image is formed Focal Length Distance between center of mirror/lens and focal point 2000 Microsoft Clip Gallery

LIGHT & ITS USES: Mirrors Plane Mirrors Perfectly flat Actually a Virtual Image Erect Image is right side up 2000 Microsoft Clip Gallery LIGHT & ITS USES: Mirrors Reflection

& Mirrors (Cont.) Convex Mirror Curves outward Reduces images. Uses: Rear view mirrors, store security CAUTION! Objects are closer than they appear! 2000 Microsoft Clip Gallery LIGHT & ITS USES: Lenses

Convex Lenses Thicker in the center than edges. Lens that converges (brings together) light rays. LIGHT & ITS USES: Lenses

2000 D. L. Power Concave Lenses Lens that is thicker at the edges and thinner in the center. Diverges light rays All images are erect and enlarged. CONVEX

CONCAVE How You See Near Sighted Eyeball is too long and image focuses in front of the retina

Far Sighted 2000 Microsoft Clip Gallery Eyeball is too short so image is focused behind the retina. 2000 Microsoft Clip Gallery LIGHT & USES: Lenses Vision Human Eye is a convex lens.

Nearsightedness Concave lenses expand focal lengths Farsightedness Convex lenses shortens the focal length. LIGHT & USES: Optical Instruments Cameras Telescopes

Microscopes 2000 Microsoft Clip Gallery 2000 Microsoft Clip Gallery 2000 Microsoft Clip Gallery LIGHT & USES: Optical Instruments LASERS

Holography Use of Lasers to create 3-D images Fiber Optics Light energy transferred through long, flexible fibers of glass/plastic Uses Communications, medicine, t.v. transmission, data

processing. Light carries information The fiber-optic networks you read about are pipelines for information carried by light. Light carries information In some cities, a fiber-optic cable comes directly into homes and apartments

carrying telephone, television, and Internet signals. LIGHT & USES: Diffraction Diffraction Bending of waves around the edge of a barrier. Breaks images into bands of light & dark and colors. Each element has it's own unique 'fingerprint' of color

Scientist identify stars based on the color emitted

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