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Name: sriram
Status: student
Age: 15
Location: N/A
Country: N/A
Date: 2000-2001


Question:
what is the difference between scattering and diffraction since in both cases waves bend at the point of contact with the object?


Replies:
Sriram,

Scattering and diffraction are both things that waves can experience, but they are not the same thing. They are not caused by the same thing. Scattering is understood in terms of particles, and behaves similarly for waves. We do not truly understand why diffraction occurs.

Scattering is effectively bouncing off something. For waves, it is being absorbed and then almost immediately released in another direction. Scattering occurs because an object gets in the way of the wave. The part of the wave that strikes the object must either pass through (light through glass), be absorbed (sunburn), or be scattered (light bouncing off the wall, so we can see the wall).

Diffraction is due to part of a wave being removed. It is an action taken by the part of the wave that does NOT strike an object. Imagine a straight wave traveling forward along the surface of the water. If you block the left half of the wave, the right half will not just keep moving forward. It will expand toward the left, toward where the blocked wave would have been. A wave seems to continuously regenerate itself, always pushing forward on itself. When a section is removed, parts of the wave get pushed in to the empty spot. It in some ways correlates to your pushing a wide row of blocks. If many people push on a few blocks each, a straight line can be maintained. If one person tries to do so, the blocks in front will tend to spread out. This is the best description of diffraction I know.

Dr. Ken Mellendorf
Illinois Central College


Hello,

In a sense both refer to light being re-directed as a result of interacting with atoms. However, a more precise definition used in optics distinguishes these two. Scattering generally implies interaction of waves (or photons) with spatially uncoordinated (unordered) atoms. This means that if one looks at a picture of the scattered radiation, one would see a spatially continuous footprint. Diffraction, on the other hand, occurs when the object or part of the object is made up of ordered atoms. These atoms, being neatly arranged, "scatter" the waves or photons in a coordinated way (i.e., in specific direction(s)) giving rise to what we can see on a film as bright spots rather.

AK

Ali Khounsary, Ph.D.
Advanced Photon Source
Argonne National Laboratory


Light scatters off of particles and surfaces. Diffraction is a special type of scattering that leads to large scale interference effects. Usually this is because the surface causing the scattering has some overall organization, such as a ruled diffraction grating or the knife edge of a slit.

Greg Bradburn


Light scatters off of particles and surfaces. Diffraction is a special type of scattering that leads to large scale interference effects. Usually this is because the surface causing the scattering has some overall organization, such as a ruled diffraction grating or the knife edge of a slit.

Greg Bradburn



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