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Anupama
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If you place a thin long wire like object horizontally in the path of a laser passed through a slit in order to obtain a diffraction pattern you will get a vertical diffraction pattern not a horizontal one. Why is it so?
I don't really know what you mean by that, but the presence of the vertical pattern is independent of the spectral content of the illuminating light. In fact, as the used light bandwidth becomes broader and broader, up to some extend the fringe contrast will get reduced due to the decreasing temporal coherence.Anyway, the reason for the vertical pattern is that the distribution of the spectral colours in a ray of light is longitudinal.
The vertical pattern is also dependent on the wavelength as the horizontal pattern although it is less marked. That's because the vertical aperture is very narrow, giving a very broad sin(x)/x pattern.The difference in levels of the different wavelengths, way off axis will be measurable but not noticeable in the region that the horizontal pattern is normally viewed. It's all simple diffraction theory here.vertical pattern is independent of the spectral content of the illuminating light.
Hmmm. Only for an infinitely long diffraction grating.There is translational symmetry along the horizontal direction, so the resulting diff pat must exhibit horizontal tranlational invariance.
Probably I should rephrase my sentence to " the presence of vertical pattern ... ". Because the particular shape of a diffraction pattern is unique to the diffracting object's shape. The change in wavelength center of the bandwidth will only scale the diffraction pattern, whereas the bandwidth will affect the fringe visibility mostly in the higher orders of the diffraction pattern.The vertical pattern is also dependent on the wavelength as the horizontal pattern although it is less marked.
The diffraction pattern is dependent on wavelength but, of course, any situation in which light (any em waves, in fact) has its amplitude or phase tinkered with in an aperture, will produce a diffraction pattern.The diffraction is highly dependent on wavelength.
Very true, in fact the fundamental formulae for diffraction such as Kirchoff and Rayleigh-Sommerfeld formulae were originally developed in an attempt to solve the the Helmholtz equation. I think it's safe to say that there is a transparent border between "diffraction" and "propagation", for example a phenomenon of beam focusing is also described by diffraction. In general, diffraction is not so different from an arbitrary beam propagation.When you get down to it, everything involving waves in space is Diffraction.
Is diffraction pattern has the same meaning / mechanism as interference pattern?The diffraction pattern is dependent on wavelength but, of course, any situation in which light (any em waves, in fact) has its amplitude or phase tinkered with in an aperture, will produce a diffraction pattern.
It is true to say that even the effect of a lens on a beam of light is, in fact, a diffraction effect. It so happens that, for a concave lens, the diffraction pattern happens to be a near-perfect image of the object and we can analyse what happens in a simpler way than using integration across the aperture, taking into account the path lengths through the lens material.
When you get down to it, everything involving waves in space is Diffraction.
I think it's fairly well accepted that the general term is Diffraction. That is what happens when a wave hits an obstruction of some sort (matter) and can be reflected, refracted or just blocked. To calculate the resulting pattern involves integrating the contributions of all infinitesimal parts of the wave front. Interference is vastly simpler and it approximates the 'interaction with matter' to the effect of a number (n) of point sources (holes in a sheet or independent antennae, loudspeakers etc.) The Interference pattern is calculated using a plain summation of n terms. It only works on the assumption the size of the holes is small enough that each hole has an omnidirectional diffraction pattern.Is diffraction pattern has the same meaning / mechanism as interference pattern?
AFAIK, diffraction only occurs when wave interacts with matter.
Diffraction can be a difficult concept to understand. To understand it first, think of it as a water wave bending around an obstacle, like a rock or a boat. This helps see what happens when a wave pattern is obstructed by an opaque obstacle. Since light has a short wavelength, it is more difficult to see the diffraction. Nevertheless, through a small slit, or double slit, one can see a diffracting pattern displayed on a light absorbing surface on the other side. This relationship between the slit size, distance from the light absorber, and slit height can all be simply mathematically expressed, but not so easily understood. For the understanding of how such variables are related I suggest looking to the Khan Academy videos. They give a great description of Youngs equation and what happens to the interference patterns as more and more slits are added in front of a light source.If you place a thin long wire like object horizontally in the path of a laser passed through a slit in order to obtain a diffraction pattern you will get a vertical diffraction pattern not a horizontal one. Why is it so?