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# Phasors Refraction And Gratings

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### Phasors Refraction And Gratings

1. 1. How can phasors explain refraction and diffraction gratings? Quantum Behaviour
2. 2. To review… <ul><li>Last lesson: </li></ul><ul><ul><li>We found out photons explore ‘all paths’ when going from a source to a detector </li></ul></ul><ul><ul><li>The path length has an effect on the orientation of the phasor when it hits the detector </li></ul></ul><ul><ul><li>If phasors ‘line up’ they increase the probability of light at that point </li></ul></ul><ul><ul><li>If phasors ‘curl up’ they reduce the probability of light at that point </li></ul></ul><ul><ul><li>Probability = Resultant 2 = Intensity </li></ul></ul><ul><ul><li>For a mirror, the shortest paths are more likely to result in light </li></ul></ul>
3. 5. Refraction with Phasors <ul><li>Today we will: </li></ul><ul><ul><li>Use the phasor model (quantum model) to explain light behaviour during </li></ul></ul><ul><ul><ul><ul><li>Refraction </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Grating </li></ul></ul></ul></ul><ul><ul><li>To start – what is the probability of light due to the phasors below..? </li></ul></ul><ul><ul><li>What is the maximum probability from this combination? </li></ul></ul>
4. 6. Resultant and Intensity <ul><li>Add all of the arrows ‘tip-to-tail’… </li></ul><ul><li>Where they ‘line up’ is where the photons make the greatest contribution </li></ul><ul><li>Where they ‘curl up’ they make the least contribution </li></ul>Phasors ‘ curl up ’ Low intensity due to these paths Phasors ‘ line up ’ High intensity due to these paths
5. 7. <ul><li>Add ‘tip to tail’ </li></ul><ul><li>Resultant = 1 therefore 1 2 = 1 </li></ul><ul><li>Maximum possible resultant = 3 </li></ul><ul><li>Maximum probability = 3 2 = 9 </li></ul>
6. 8. Refraction <ul><li>Let’s try the same thing with Refraction… </li></ul>
7. 9. Refraction <ul><li>With refraction, the phasors travel at different speeds in different media. </li></ul><ul><li>Light also changes direction – does quantum theory support this? </li></ul>
8. 10. Curved Mirrors and Gratings <ul><li>To make photons ‘line-up’ there are 2 others ways: </li></ul><ul><ul><li>Curved mirror </li></ul></ul><ul><ul><li>Grating </li></ul></ul>
9. 11. Curved Mirror <ul><li>With a plane (flat) mirror, there is not much chance of photons ‘lining-up’ at the detector </li></ul>
10. 12. Curved Mirror <ul><li>With a curved mirror, there is more chance of photons ‘lining-up’ at the detector </li></ul>
11. 13. Gratings <ul><li>A Grating gives a pattern due to constructive and destructive interference in the waves explanation of light. </li></ul>But can we explain this using ‘quantum theory’?