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Introduction To Phasors And Probability

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Introduction To Phasors And Probability

1. 1. How can light be represented by phasors? Quantum Behaviour
2. 2. Phasors and Superposition <ul><li>We will find out: </li></ul><ul><ul><li>How light can be represented by phasors to show constructive and destructive interference </li></ul></ul><ul><ul><li>How photons can be assumed to go ‘anywhere’ </li></ul></ul><ul><ul><li>How to work out the probability of a photon arriving at a certain place </li></ul></ul>
3. 3. Phasors <ul><li>Phasors represent waves in terms of: </li></ul><ul><ul><li>Amplitude – Length </li></ul></ul><ul><ul><li>Frequency – Number of turns on 1 second </li></ul></ul>But a photon also has frequency but the magnitude is arbitrary in this case
4. 4. Phasors and Interference <ul><li>When more than one phasor interact, they interfere. </li></ul><ul><li>We add them ‘tip-to-tail’ to see the outcome – constructive or destructive interference </li></ul>In Phase – Phasors Add  /2 out of phase Out of Phase – Phasors Cancel Resultant The phasor magnitude is normally 1
5. 5. Phasors <ul><li>But how do we know the phase of a phasor at any one time..? </li></ul><ul><li>It depends on the path! </li></ul><ul><li>But how does the phasor know which path to take..? </li></ul>
6. 6. Calculating Phase Position <ul><li>Phasors leave a source in phase – i.e. lined up </li></ul><ul><li>To calculate their relative phase at a time and path length we use: </li></ul><ul><li>Trip Time = Distance / Speed </li></ul><ul><li>Speed = f x  = c where c = speed of light = 3 x 10 8 m/s </li></ul><ul><li>Number of Rotations = Rotations per second x Number of seconds </li></ul>This is frequency
7. 7. Question 10s <ul><li>Complete the questions using the 3 equations </li></ul><ul><li>Trip Time = Distance / Speed </li></ul><ul><li>Speed = f x  = c where c = speed of light = 3 x 10 8 m/s </li></ul><ul><li>Number of Rotations = Rotations per second x Number of seconds </li></ul>