What is light

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What is light

  1. 1. What Is Light? In this Powerpoint presentation:1) Properties of light2) Colors )3) Reflection - Mirrors f4) Refraction - Lenses
  2. 2. Properties of LightLight travels in straight lines:LASER
  3. 3. Light travels much faster than sound. For example: 1) Thunder and lightning start at the same time, but we will see the lightning first. 2) When a starting pistol is fired we see the smoke first and then hear the bang.
  4. 4. Light travels VERY FAST – about 300,000 kilometers per second or 186,000 186 000 miles per second second.At this speed lightcould travel theequivalent of 8 times q faround the world inone second!
  5. 5. Light can create shadowsShadows are places where light is “blocked”: Rays of light
  6. 6. Light travels in wavesA wave is a disturbance that transfers energy from place to place. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
  7. 7. What characteristics do light waves h have? ?Light waves are like other kinds of waves. They have crests, troughs, wavelength, frequency and speed. However, light waves are electromagnetic! Light waves have a component that is electric and magnetic!! QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
  8. 8. We see things because they g y reflect light into our eyes! Thisis literally the only way we get to see things! ALL objects we see either create light or reflect light!! Homework H k
  9. 9. Light is a form of energy called Electromagnetic Radiation -Electromagnetic Radiation comes fEl i R di i from the sun and h d other sources QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
  10. 10. Electromagnetic Radiation•Travels at the speed oflight•Is mostly i i ibl I tl invisible•Carries energy•Is VERY important to Is QuickTime™ and a TIFF (Uncompressed) decompressorsociety and is something are needed to see this picture.YOU can’t be without formany reasons
  11. 11. Types of electromagnetic radiationRadio and TV - Great for broadcastingMicrowave-Super for cell phones, microwavesInfrared-Think HEATVisible Light - Yep, it’s how we seeUltraviolet Invisible, can cause c ncer;Ultr vi let - Invisible c n c use cancer; kills germs ermsXray- images of bones and teeth; space explorationGamma - treating cancer (radiation therapy)
  12. 12. Properties of Light summary1) Light travels in straight lines and is a form of energy2) Light travels much faster (a million times faster!) than sound3) We see things because they reflect light into our eyes e es4) Shadows are formed when light is blocked by an object5) Visible light is only a small part of the electromagnetic spectrum; the other parts are invisible to the human eye but not necessarily the um y u y eyes of other animals.
  13. 13. Part 2 - Reflection and Mirrors
  14. 14. Regular vs. Diffuse ReflectionSmooth, shiny surfaces m , y u f have a regular reflection:Rough, dull surfaces have h d ll f ha diffuse reflection.Diffuse reflection is whenlight is scatt r in ght s scattered ndifferent directions
  15. 15. Using mirrorsTwo examples: 2) A car headlight 1) A periscope
  16. 16. Types of Mirrors: Plane, Concave, Convex QuickTime™ and a TIFF (Uncompressed) decompressor QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.Plane mirrors are flat and make “virtualimages”. Th images is “virtual” because theim s” The im s i t l” b s thlight rays do not come from the image, theyonly appear to
  17. 17. Concave Mirrors are curved inward - just remember, you go “i ” t a cave, and “in” to a b “in” to d “i ” t concave mirror! Virtual Real QuickTime™ and a images TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a image TIFF (Uncompressed) decompressor QuickTime™ and a are needed to see this picture. TIFF (Uncompressed) decompressor are needed to see this picture. The “mirage” box on Mr. S’s desk is g made of two concave mirrors. Images of concave mirrors can be virtual or real! i t l l! QuickTime™ and a QuickTime™ and a TIFF (Uncompressed) decompressorTIFF ( (Uncompressed) decompressor ) are needed to see this picture. are needed t see thi picture. d d to this i t
  18. 18. Convex mirrors are mirrors that curve outward QuickTime™ and a TIFF (Uncompressed) decompressor QuickTime™ and a QuickTime™ and a are needed to see this picture picture. TIFF (Uncompressed) decompressor ( p ) p are needed to see this picture. d d hi i TIFF (Uncompressed) decompressor are needed to see this picture. Convex mirrors are used for security purposes, in cars etc. They ll Th allow us to see a wide st s id QuickTime™ and aTIFF (Uncompressed) decompressor are needed to see this picture. view. The images they make are virtual QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture picture.
  19. 19. Review of Reflection1. Two types of reflection, regular and diffuse2. Mirrors come in 3 types: plane, convex and concave. Each has a distinct shape and use.3. Mirrors can make virtual images or real images depending on their type4. Virtual images - light rays do not meet and the image is always upright or right-side-up m g y p g g p5. Real images - always upside down and are formed when light rays actually meet
  20. 20. Refraction•Refraction is when waves speed up or slow down due totravelling in a different medium g•A medium is something that light waves will travelthrough•Light rays are slowed down by the water•Causes the ruler to look bent at the surface• The mediums in this example are water and air
  21. 21. The degree that light bends when it enters a g gnew medium is called the “index of refraction”
  22. 22. Light hittingLight hitting at an straight on isangle is bent not bent
  23. 23. Lenses work because of refraction! Light isbent as it enters a new medium glass! medium, Convex lenses QuickTime™ and a QuickTime™ and aTIFF (Uncompressed) decompressor QuickTime™ and a picture. are needed to see this picture TIFF (Uncompressed) decompressor ( p ) p TIFF (Uncompressed) decompressor ( p ) p are needed to see this picture. are needed to see this picture. 1. 1 Thicker middle, Thick r in middl thin on edges n d s 2. Light rays meet to form a focal point 3. 3 Makes real images since light rays come together from a light source, but can also make virtual images (center picture) 4. Used i 4 U d in cameras, t l telescopes, human eye h QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
  24. 24. Concave Lenses QuickTime™ and a QuickTime™ and aTIFF (Uncompressed) decompressor TIFF (Uncompressed) decompressor are needed to see this picture. are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture picture. 1. Concave lenses are thin in the middle and thicker on the edges 2. Since light rays never meet with this lens, they make virtual images only 3. Used in cameras & telescopes to correct spherical aberation, and also eyeglasses
  25. 25. Review of Refraction1. Light rays slow down when they enter a new medium di2. Refraction can cause light rays to change their direction3. All transparent materials have their own p “index of refraction”4.4 Light is refracted when it passes through lenses and this creates images
  26. 26. ColorPart 3 - Color In this section of the Powerpoint you will learn about color and how we can mix colors to create other colors. We will also learn how light helps us to see various colors around us us.
  27. 27. Yes, we LOVE color! QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
  28. 28. ColorWhite light is not a single color; it is made up of a mixture of the seven colors of the rainbow.We can demonstrate this bysplitting white light with aprism:This is how rainbows areformed: sunlight is “split up” g p pby raindrops.
  29. 29. The colors of the rainbow: Red Orange Yellow Green Blue IndigoJust remember ROY G. BIV Violet
  30. 30. Adding colors of light White light can be split up to make separate colors. These colors can be added together again. The primary colors of light are red, blue and green:Adding blue and red Adding blue andmmakes magenta m g green makes cyan g m y(purple) (light blue)Adding red Adding alland green g three makesmakes yellow white again
  31. 31. Seeing colorThe color an object appears depends on the colors of light it reflects.For example, a red book only reflects red light: p y g White Only red light light is reflected fl d
  32. 32. In different colors of light this shirt would look different: Red Shirt looks red light Shorts look black Shirt looks black Blue light Shorts look blue
  33. 33. A pair of purple trousers would reflect purple light(and red and blue, as purple is made up of red and blue): Purple light A white hat would reflect all seven colors: White light
  34. 34. Using filtersFilters can be used to “block” out different colours of light: Red R d Filter Magenta Filter Fl
  35. 35. Some further examples: Color object Object Color of light seems to be Red Red Red socks Blue Black Green Black Red Black Blue teddy Blue Green RedGreen camel Blue Green RedMagenta book Blue Green
  36. 36. Investigating filtersColor of filter Colors that could be “seen” seen Red Green Blue Cyan Magenta Yellow
  37. 37. Red Blue Green WhiteYellow Cyan Magenta
  38. 38. Part 2 - Reflection and Mirrors MiReflection from a mirror: NormalIncident ray y Reflected ray y Angle of Angle of incidence reflection Mirror
  39. 39. The Law of Reflection Angle of incidence = Angle of reflectionIn other words, light gets reflected from a surface at g g____ _____ angle it hits it. The Th same !!!
  40. 40. Brain Pop Movie on Color p Brain Pop Movie on Color! Enjoy it! p j yView the movie on Color from Brain Pop. Then take the pquiz at the end of the movie. How did you do?

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