Wave Optics

Diffraction


  • Diffraction Confirms wave nature of Light
  • The Light waves are diffracted only when the size of the obstacle is comparable to the wave length of Light.
  • Condition for observing diffraction.
    \tt l\approx\frac{b^{2}}{4\lambda}
    l = distance between screen and object
    b = size of object
  • In Fresnels diffraction sources and screen are at finite distance
  • No Lenses are required in fresnels diffraction.
  • The incident wave fronts in Fresnels diffraction are either spherical (or) cylindrical.
  • In Fraunhoffer diffraction source and screen are at infinite distance
  • Lenses are required to observe the fraunhoffer diffraction.
  • The incident wave fronts in Fraunhoffer diffraction are plane wave fronts.
  • Fraunhoffer diffraction is limiting case of fresnels diffraction.
  • Condition for minimum intensity in fraunchoffer a sin θ = nλ {n = 1, 2, 3 …….} (a = width of slit)
  • Condition for miximum intensity in fraunchoffer \tt a \sin\theta=\left(2n+1\right)\frac{\lambda}{2} {n = 1, 2, 3 …….} (a = width of slit)
  • Width of central maxima\tt \beta_{0}=\frac{2D\lambda}{a}=\frac{2f\lambda}{a}

View the Topic in this video From 00:18 To 8:11

Disclaimer: Compete.etutor.co may from time to time provide links to third party Internet sites under their respective fair use policy and it may from time to time provide materials from such third parties on this website. These third party sites and any third party materials are provided for viewers convenience and for non-commercial educational purpose only. Compete does not operate or control in any respect any information, products or services available on these third party sites. Compete.etutor.co makes no representations whatsoever concerning the content of these sites and the fact that compete.etutor.co has provided a link to such sites is NOT an endorsement, authorization, sponsorship, or affiliation by compete.etutor.co with respect to such sites, its services, the products displayed, its owners, or its providers.

Diffraction of a single slit:
1. For minima d sin θ = nλ, where n = 1, 2, 3 .....
2. For maxima d sin θ = (2n + 1)\frac{\lambda}{2}, where n = 1, 2, 3 ....