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Wave Optics ( Physical Optics ) Double Slit and thin Film Interference

Chapter 27. Wave Optics ( Physical Optics ) Double Slit and thin Film Interference. What is physical optics. It is the study of light as waves. Geometric optics treats light as particles (or rays) that travels in straight lines.

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Wave Optics ( Physical Optics ) Double Slit and thin Film Interference

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  1. Chapter 27 Wave Optics (Physical Optics )Double Slit and thin Film Interference

  2. What is physical optics • It is the study of light as waves. • Geometric optics treats light as particles (or rays) that travels in straight lines. • Physical optics (wave optics) deals with the wave nature of light, such as the spreading of waves (diffraction) and the interference of waves.

  3. Adding waves Constructive interference Destructive interference Combining two waves does not always give you a bigger wave!

  4. Destructive Shift by half a wavelength Constructive

  5. Constructive interference Distance to the left: 2λ Distance to the right: 2λ Crests always arrive at the same time as crests Troughs always arrive at the same time as troughs λ

  6. Constructive interference Distance to the left: 3λ Distance to the right: 1λ Crests always arrive at the same time as crests Troughs always arrive at the same time as troughs λ

  7. In general (constructive) Constructive interference occurs whenever the path difference is an integral multiple of λ:

  8. Destructive interference Distance to the left: 2λ Distance to the right: 1.5λ Crests always arrive at the same time as troughs λ

  9. In general (destructive) Destructive interference occurs whenever the path difference is an half-integral multiple of λ:

  10. The same is true in 2d (constructive)

  11. The same is true in 2d (destructive)

  12. Phase difference and path difference

  13. Interference on water

  14. Ripples

  15. It is all about path difference

  16. Young’s Double Slit (1800)

  17. What are the fringes? The bright fringes represents regions of high intensity I The dark fringes represents regions of low intensity.

  18. Why is I high here? r1 r2 Constructive Interference! the middle Light can reach this place via two paths, r1 and r2. Path difference is:

  19. What about the other fringes?

  20. Bright and dark fringes

  21. Calculating the angle

  22. What you see

  23. Example Given λ = 700nm and d = 3500nm, find the angles at which you can find the 0th, 1st and 2nd order maxima. What if you double d? (Notation: m = order ) d

  24. Radio broadcast The frequency f =1.5×106Hz, from two antennas shown below. In what directions will you find the strongest signal?

  25. Position on the screen

  26. Position on the screen (Approximation)

  27. Position on the screen (Approximation)

  28. Find the wavelength

  29. Find the wavelength

  30. Find the wavelength (Alternative)

  31. Intensity

  32. Wavelength in different medium

  33. Wavelength in different materials

  34. Example Assuming θ =0°, λ=550nm, nMgF = 1.38, what is the smallest L so that the two light rays shown will cancel out each other?

  35. Interference around us

  36. Soap bubbles

  37. Newton’s rings

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