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Electromagnetic waves are emitted by the Sun and other stars Do not require a medium to travel

The Electromagnetic Spectrum. Electromagnetic waves are emitted by the Sun and other stars Do not require a medium to travel EM waves all travel at the same speed of light , 300,000,000 m/s, but they have different wavelengths and different frequencies. Radio Waves.

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Electromagnetic waves are emitted by the Sun and other stars Do not require a medium to travel

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  1. The Electromagnetic Spectrum • Electromagnetic wavesare emitted by the Sun and other stars • Do not require a medium to travel • EM waves all travel at the same speed of light, 300,000,000 m/s, but they havedifferent wavelengths and different frequencies

  2. Radio Waves • Radio Wavescarry information and entertainment through radio and television • Have the longest wavelength & lowest frequency of all EM waves • AM Radio Waves are the slowest traveling radio waves • Range: 600 – 200 m • Longest wavelength of all EM waves • FM Radio Waves • Range: 5.5 – 0.187 m • Uses: • Amateur and government radio • International broadcasting • Interesting Fact: 10% of the static you hear between radio stations is background radiation from outer space!

  3. Microwaves • Microwavesare classified as being radio waves with the shortest wavelengths and the highestfrequencies • Range: 187 - 10 mm • Uses: • Heating Food(Microwave ovens give off EM waves that bounce around inside the oven, penetrating the food. Water molecules inside the food absorb the energy and in turn cause the food to get hot) • Transmit cell phone calls *Interesting Fact:* Microwave radiation can pass through certain materials like plastic and glass, but are blocked by metals, which create sparks and even fire as they bounce off– so no spoons in the microwave!

  4. Infrared Waves • Infrared Rays– the prefix Infra- in Latin means “below,” so the name means “below red.” • Invisible to the naked eye • Can feel them as heat • Most objects give off infrared rays • Contributes to the Greenhouse Effect • Range: 1 mm – 750 nm • Uses: • Heating food • Detecting people or animals in the dark • Studying the growth of plants • Observing motions of clouds to help determine weather patterns A thermograph of an elephant

  5. Visible Light • Visible Lightis the only part of the EM spectrum that you can see • Range: 750 – 400 nm • Uses: Each wavelength of EM light shows to our eyes as a different color • ROY G BIV • red, orange, yellow, green, blue, indigo, violet • Red has longest light wavelength • Violet has shortest light wavelength

  6. Ultraviolet Waves • UltravioletRays– the prefix Ultra- in Latin means “beyond,” so the name means “beyond violet” • Range: 400 nm – 10 nm • Uses: Since they have a higher frequency than visible light, they carry more energy • Can burn skin, cause skin cancer or damage your eyes • Small doses provides vitamin D, needed for healthy bones and teeth • Energy is great enough to damage or kill bacteria or living cells • Used to treat jaundice

  7. X-Rays • X-raysare EM waves with very short wavelengths • Range: 10 nm – and below • Uses: Carry more energy than UV rays and can penetrate most matter • Make images of bones inside the body • X-rays pass through skin and soft tissues and cause the photographic film to darken when it is developed • Denser matter (lead or bone) absorbs X-rays and does not allow them to pass, so image shows up lighter • Airport Security • *Too much exposure can cause cancer

  8. Gamma Rays • Gamma Rays– have the shortest wavelength and the highest frequency of all EM waves that carry the greatest amount of energy • Range: < 10-12 m • Uses: Are the most penetrating of the EM waves • Can cause serious illnesses • When used in controlled conditions, can kill cancer cells in radiation treatments • Examine the body’s internal structures Objects far out in space emit gamma rays, which must travel billions of years before reaching Earth

  9. What happens to light rays when they hit an object? • When light rays hit an object, they are either: • Reflected • Refracted • Absorbed • Transmitted(pass through the object) • What you see of an object depends on how the surface of it reflects light

  10. In White Light... • Parts of objects absorb some wavelengths of light and reflects all others • The color black – absence of color • all colors are absorbed • no colors are reflected • The color white – all colors • all colors are reflected • no colors are absorbed • can be refracted in a prism to see all of the colors

  11. Seeing Color The Color Red Absorbs: Orange, yellow, green, blue, indigo, violet Reflects: RED The Color Yellow Absorbs: Red, orange, green, blue, indigo, violet Reflects: YELLOW The Color Blue Absorbs: Red, orange, yellow, green,indigo violet Reflects: BLUE

  12. In Colored Light... • Objects can appear different colors depending on the color of light in which they are seen • Ex: Water at sunset • Objects seen through filters • Color filters only allow certain colors to pass through them, absorbing or reflecting the rest

  13. Primary Colors • Primary Colors- Three colors that can be used to make any other color • Two types of primary colors • Primary Light Colors • Images produced in TVs, computers, phones, etc. are made up of only red, green and blue • Primary Pigment Colors • Colors in print are all made up of various shades of magenta, yellow and cyan

  14. Primary Light Colors • Primary Light Colors – Red, green, and blue colors, which when combined in equal amounts, produce white light. • Secondary Light Color – a color produced by two primary colors • RED + GREEN = YELLOW • RED + BLUE = MAGENTA • BLUE + GREEN = CYAN • RED + GREEN + BLUE = WHITE • Ex: Television screen pictures are made up of only red, green and blue lights so the images are all produced by varying the amounts of each color that is shown

  15. Primary Pigment Colors • Colors we see in the world around us are considered to be “pigments” • Primary Pigment Colors – magenta,yellow,cyancolors, which when combined in equal amounts, produce the color black • Secondary Pigment Colors: The color you see is the color of light that particular pigment reflects • CYAN + YELLOW = GREEN • CYAN + MAGENTA = BLUE • YELLOW + MAGENTA = RED • CYAN + Yellow + MAGENTA = BLACK • Artists create different shades of colors using paints and dyes of both primary and secondary pigments

  16. How we see...transmitted light • Different objects allow different amounts of light to pass through them • The amount of light that passes through an object can be described as: • Transparent • Translucent • Opaque

  17. Objective 11/20/2012 Page 58 SWBAT relate the light we see to the reflections of light through notes and review Jumpstart In your own words, explain why we see the sky as blue, but an egg as white. Hint: Be sure to include what is being ‘absorbed’ and ‘reflected’.

  18. Reflection of Light Notebook Page 59 Packet 5 Page 5

  19. How we see...reflected light • 3.8- THE STUDENT WILL EXPLAIN THAT AN OBJECT IS SEEN WHEN LIGHT REFLECTED FROM AN OBJECT ENTERS THE EYE. [P8C1] Page 4 • Rays of light usually travel in straight lines until they hit something • You can see objects because light reflects or bounces off of them. • What you see depends on how surface light is reflected from an object. • The light that reflects off the surface of an object must reach our eyes in order for us to see it Page 5 • Color the fruit • Red apple, yellow banana, purple grapes, green pear • Color the arrow from the fruit in the color that is reflected!

  20. Page 5- Regular Reflection • “Good reflection” • Occurs when parallel rays of light hit a smooth surface and all of the rays are reflected at the same angle • You can see your reflection from a surface that reflects regularly. • Mirror- Glass with a silver coating on one side that reflects light regularly • Plane Mirror- smooth, flat • Images are upright • Images are same size as reflected object • Concave Mirror- curves inward • Images are enlarged if close • Images are up side down if you are far away • Convex Mirror- curves outward • Light rays spread out and appear to meet at a focal point behind the mirror

  21. Regular Reflection • Occurs when parallel rays of light hit a smooth or flat surface. • All rays are reflected at the same angle. (reflected regularly)

  22. Diffuse Reflection • Diffuse reflection – (poor reflection) occurs when parallel rays of light hit a bumpy or uneven surface; light rays are reflected in all different angles • Allows you to see the object but not your reflection. • Most objects reflect light diffusely.

  23. Diffuse reflection Regular vs. Diffuse Reflection of Light Regular reflection

  24. Mirrors and Lenses Video- Page 5

  25. The Law of Reflection The Law of Reflection states that the angle of incidence is equal to the angle of reflection

  26. Law of Reflection • Ray- Straight line used to represent a light ray • Angle of Incidence (i) - The angle at which the ray hits the surface (measured from an imaginary perpendicular line) • Angle of Reflection (r) - The angle of the rays bouncing off a surface • Law of Reflection - The angle of incidence = angle of reflection • Normal - The perpendicular direction to a given surface; the point of reference for measuring angles that hit surfaces • Drawn as a dashed line! - - - - - - - -

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