WAVES: SOUND & LIGHT Waves carry energy from one place to another © 2000 Microsoft Clip Gallery

NATURE OF WAVES Waves (Def.) – A wave is a disturbance that transfers energy. Medium – Substance or region through which a wave is transmitted. Speed of Waves – Depends on the properties of the medium. © 2000 Microsoft Clip Gallery

LIGHT: What Is It? 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

Transverse Waves Energy is perpendicular to direction of motion © 2000 Microsoft Clip Gallery

Compression or Longitudinal Waves

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 AM – Carries audio for T.V. Broadcasts Longer wavelength so can bend around hills FM – Carries video for T.V. Broadcasts © 2000 Microsoft Clip Gallery

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

Microwave  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) speed-monitoring radar satellite station

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 e sp. 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

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.)

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

Color of Light (Cont.) Color of Objects White light is the presence of ALL the colors of the visible spectrum. Black objects absorb ALL the colors and no light is reflected back. © 2000 Microsoft Clip Gallery

How You See 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 © 2000 Microsoft Clip Gallery

Human Eye Diagram

LIGHT & ITS USES Sources of Light Incandescent light – light produced by heating an object until it glows. © 2000 Microsoft Clip Gallery

LIGHT & ITS USES Fluorescent Light – Light produced by electron bombardment of gas molecules Phosphor coating absorb photons that are created when mercury gas gets zapped with electrons. The phosphors glow & produce light. © 2000 Microsoft Clip Gallery

LIGHT & ITS USES - Neon Neon light – neon inside glass tubes makes red light. Other gases make other colors. © 2000 Microsoft Clip Gallery

Compact Fluorescent lights Energy Efficient Designed to replace incandescent lights Must be disposed of properly DANGERS: Mercury poisoning Destroys neurons

LIGHT & ITS USES - Reflection Reflection – Bouncing back of light waves

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

CONVEX CONCAVE

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