Properties of light


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  • Light and its nature have caused a lot of ink to flow during these last decades. Its dual behavior is partly explained by (1)Double-slit experiment of Thomas Young - who represents the photon’s motion as a wave - and also by (2)the Photoelectric effect in which the photon is considered as a particle. A Revolution: SALEH THEORY solves this ambiguity and this difficulty presenting a three-dimensional trajectory for the photon's motion and a new formula to calculate its energy. More information on or
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Properties of light

  2. 2. Light
  3. 3. Part 1 – Properties of Light <ul><li>Light travels in straight lines: </li></ul>Laser
  4. 4. <ul><li>Light travels VERY FAST – around 300,000 kilometres per second. </li></ul>At this speed it can go around the world 7.5 times in one second.
  5. 5. <ul><li>Light travels much faster than sound. For example: </li></ul><ul><li>Thunder and lightning start at the same time, but we will see the lightning first. </li></ul>2) When a starting pistol is fired we see the smoke first and then hear the bang.
  6. 6. <ul><li>Luminous and non-luminous objects </li></ul>A luminous object is one that produces light. A non-luminous object is one that reflects light. Luminous objects Nonluminous objects
  7. 7. <ul><li>Shadows </li></ul>Shadows are places where light is “blocked”: Rays of light
  8. 8. Properties of Light summary <ul><li>Light travels in straight lines </li></ul><ul><li>Light travels much faster than sound </li></ul><ul><li>We see things because they reflect light into our eyes </li></ul><ul><li>Shadows are formed when light is blocked by an object </li></ul>
  9. 9. How do we see objects?
  10. 10. <ul><li>We see things because they reflect light into our eyes: </li></ul>Homework
  11. 11. Reflection
  12. 12. Reflection of Light <ul><li>is the phenomenon of wave motion, in which a wave is returned after impinging on a surface. </li></ul>
  13. 13. <ul><li>Types of </li></ul><ul><li>Reflection </li></ul>
  14. 15. Specular Reflection <ul><li>Reflection off of smooth surfaces such as mirrors or a calm body of water. </li></ul>
  15. 16. Diffuse Reflection <ul><li>Reflection off of rough surfaces such as clothing, paper, and the asphalt roadway. </li></ul>
  16. 17. <ul><li>Applications </li></ul>
  17. 18. <ul><li>One application pertains to the relative difficulty of night driving on a dry asphalt roadway compared to a wet asphalt roadway. </li></ul>
  18. 20. The Law of Reflection The incident ray, the reflected ray, and the normal to the surface all lie in the same plane, and the angle of reflection θ r equals the angle of incidence θ i.
  19. 22. <ul><li>The ray of light approaching the mirror is known as the incident ray (labeled I in the diagram). The ray of light which leaves the mirror is known as the reflected ray (labeled R in the diagram). </li></ul>
  20. 23. <ul><li>At the point of incidence where the ray strikes the mirror, a line can be drawn perpendicular to the surface of the mirror; this line is known as a normal line (labeled N in the diagram). </li></ul>
  21. 24. <ul><li>The angle between the incident ray and the normal is known as the angle of incidence . </li></ul>
  22. 25. <ul><li>The angle between the reflected ray and the normal is known as the angle of reflection . </li></ul>
  23. 26. Reflection <ul><li>Reflection from a mirror: </li></ul>Incident ray Normal Reflected ray Angle of incidence Angle of reflection Mirror
  24. 27. <ul><li>The Law of Reflection </li></ul>Angle of incidence = Angle of reflection In other words, light gets reflected from a surface at ____ _____ angle it hits it. The same !!!