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INTRODUCTION TO REFRACTION 12.1, 12.4, 12.5

INTRODUCTION TO REFRACTION 12.1, 12.4, 12.5. Long wave vs. Short wave in a race. How a short wave keeps up with a long wave in a race. Deep. Shallow. But light isn’t water waves…and it still doesn’t explain how it bends. http://www.regentsprep.org/Regents/physics/phys04/crefractn/default.htm.

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INTRODUCTION TO REFRACTION 12.1, 12.4, 12.5

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  1. INTRODUCTION TO REFRACTION12.1, 12.4, 12.5

  2. Long wave vs. Short wave in a race

  3. How a short wave keeps up with a long wave in a race

  4. Deep Shallow

  5. But light isn’t water waves…and it still doesn’t explain how it bends • http://www.regentsprep.org/Regents/physics/phys04/crefractn/default.htm

  6. NEED AN ANGLE

  7. AIR: MED 1 INCIDENT RAY NORMAL REFRACTED RAY PARTIALLY REFLECTED RAY INCIDENT RAY BOUNDARY GLASS: MED 2 AIR: MED 2 GLASS: MED 1 NORMAL BOUNDARY REFRACTED RAY

  8. CONVENTIONS FOR REFRACTION INCIDENT RAY MEDIUM 1 i BOUNDARY R REFRACTED RAY MEDIUM 2

  9. WHAT DO YOU NOTICE ABOUT THE ANGLES OF REFRACTION? • Compare the incident and refracted angle in moving from: • Air to glass • Glass to air • Notice how: • θi > θr when moving from air to glass • θi < θr when moving from glass to air

  10. Effects of refraction • http://www.upscale.utoronto.ca/PVB/Harrison/Flash/Optics/Refraction/Refraction.html

  11. INDEX OF REFRACTION (n) • Ratio of the speed of light in a vacumn relative to the speed of light in a given media • Constant value calculated for various substances • n = c v Where: c = speed of light in a vacumn v = speed of light in a given medium Notice that the slower light moves in a medium (decrease v) the greater the index of refraction will be

  12. TOTAL INTERNAL REFLECTION • Occurs when a light ray moves from a more optically dense medium (slow) to a less optically dense medium (fast) • Light bends away from normal • If index of refraction of fast medium is low, light leaving the medium will bend further away from the normal • If the light bends so much that it is “parallel” to the boundary of the medium, (ie. Θr = 90o), then the light ray is completely reflected back into the slow medium

  13. CRITICAL ANGLE θC • The angle at which this occurs is known as the CRITICAL ANGLE • At this point, 100% of the light ray reflects instead of refracting

  14. Did you know…that the “brilliant” cut for a diamond maximizes the total internal reflection of light to make the diamond “sparkle”? Diamond has a very high index of refraction: 2.4

  15. Index of refraction and critical angle • For optically dense substances in air (so light is travelling from the substance into air), as the index of refraction for a substance increases, the critical angle decreases • This ensure that more and more of the light rays that are trying to move from the slow to the fast medium will be greater than critical angle, so the it becomes harder for the light ray to refract out of the slow medium and into the fast

  16. DISPERSION • The colour of light is determined by the frequency of light • Different colours have different frequencies and wavelengths • White light is made up of a mixture of all frequencies of light • When white light hits a prism – causes the light to refract • Each colour of light does that differently since they all have different frequencies

  17. Did you know…that rainbows are created after a rainfall due to dispersion? When light travels through the water droplets in the atmosphere they refract and disperse the white light to create a rainbow

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