- Slides: 64
© 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
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 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 can’t 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 cont’d 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 cont’d Another example of refraction of light is the twinkling of a star in the night sky As starlight travels from space into the Earth’s 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
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
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 don’t 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 things Colored fabrics and 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 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 See…again © 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 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 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 © 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.
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
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 fiberoptic cable comes directly into homes and apartments carrying telephone, television, and Internet signals.
LIGHT & USES: 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