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Wave nature of light

Wave nature of light. Light is an electromagnetic wave. EM waves are those waves in which there are sinusoidal variation of electric and magnetic fields at right angles to each other as well as to the direction of propagation of wave. WAVE OPTICS. WAVEFRONT

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Wave nature of light

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  1. Wave nature of light • Light is an electromagnetic wave. • EM waves are those waves in which there are sinusoidal variation of electric and magnetic fields at right angles to each other as well as to the direction of propagation of wave.

  2. WAVE OPTICS • WAVEFRONT The locus of all the points where the waves from a given source reach at given instant of time.

  3. Spherical wavefront

  4. Cylindrical wavefront

  5. 1. Plane wavefront

  6. Two phenomenon explaining wave nature of light. Diffraction and interference are similar phenomena. Interference is the effect of superposition of 2 coherent waves. Diffraction is the superposition of many coherent waves Diffraction and Interference

  7. Huygens’ principle • Every point on the given wave front acts a fresh source of new disturbance called secondary wavelets which travel in all directions. • The new wavefront at any instant will be the envelope of the secondary wavelets at that instant

  8. Huygen’s Picture of a Plane wave

  9. Huygen’s Explanation of Reflection

  10. Huygen’s Explanation of Refraction

  11. Young’s double slit experiment: classic wave effect

  12. Young’s double slit experiment Interference of light is the phenomenon of redistribution of light energy in a medium on account of superposition of light waves from two coherent sources

  13. Formation of crests n troughs

  14. Double slit experiment with particles (e.g. electrons) Interference pattern with one slit blocked

  15. Double slit experiment with particles (e.g. electrons) Interference pattern observed on the screen When both the slits are open

  16. Diffraction When light waves hit an obstacle it bends around the edges of the obstacle. • This property of bending of light is called diffraction. • For example, if light of red wavelength from a laser source hits a small hole, it bends around the edges of the hole and forms a pattern called an Airy disc pattern.

  17. Single slit diffraction • Diffraction occurs on account of mutual interference of secondary wavelets starting from the portions of wave front which are allowed to pass from the aperture.

  18. The pattern spreads out due toDiffraction. Wave picture Light spreads out when passed through small aperture.

  19. Position of maxima a sin θ n= (2n+1)λ/2 Position of minima: a sin θ n= nλ

  20. Polarization If unpolarized light is incident on 1 polarizer, the intensity of the light passing through is I= ½ I0.

  21. Polarization & Scattering • Light scattered at 90 degrees is 100% polarized.

  22. A polarizer will transmit linear polarized waves in the same direction independent of the incoming wave.

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