Confusion about the nature of Diffraction.

[siddharth5129]

Why does the size of an obstacle have to be comparable to the wavelength of radiation for diffraction effects to be noticable ? Secondly, if the size of an opening is much smaller than the wavelength of the radiation , how does the radiation interact with the opening ? Third, can the same things be concluded for phonons traveling in a crystal lattice, or mechanical waves on a string ?

 

[CWatters]

Why does the size of an obstacle have to be comparable to the wavelength of radiation for diffraction effects to be noticable ?

The amount of light that goes straight through a wide aperture is large compared to the amount that is diffracted by the edges of the aperture.

 

[jtbell]

Do a Google search for "Fresnel diffraction" and you'll find examples of diffraction at the edges of a wide aperture. Also try "knife edge diffraction" for diffraction at a single edge (semi-infinite aperture).