A Question about Diffraction....

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In Summary, the greater or maximum diffraction occurs when the gap between the slit and the wave is comparable to the wavelength of the wave. This results in a more perfect semi-circle around the barrier, which diffracts more light.
  • #1
Kaneki123
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Okay...I have a question that, I have often read the statement in various topics on diffraction that "Diffraction is maximum when slit is comparable to wavelength of wave". Can someone point out what is exactly meant by ''greater or maximum diffraction'' here?...Like if we are going to talk about in the sense that "diffraction is greater when water waves, after passing through the slit, bend upto the "outer surface" of the slit", then is'nt that what happens in ''every'' diffraction, if we are to consider Hyugens Principle?...Any help is appreciated...
P.S: I know my question does not make much sense, so i will try my best to elaborate it in my replies...
 
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  • #2
In the first image, the water waves after passing through the slit, form an almost semi-circular shape...However, in the second image, the water waves form the same almost semi-circular shape, even though gap between obstacles in the two images is not same...So what is this "greater diffraction"?...I hope my question makes some sense now...
 

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  • #3
The more light is diverted from the straight-through horizontal direction, the greater is the diffraction.
 
  • #4
pixel said:
The more light is diverted from the straight-through horizontal direction, the greater is the diffraction.
If you look very closely at the two images i posted, you can see that there is the same semi-circular shape of water waves in both images...So where is this "more bending of light in greater diffraction"?
 
  • #5
Kaneki123 said:
If you look very closely at the two images i posted, you can see that there is the same semi-circular shape of water waves in both images...So where is this "more bending of light in greater diffraction"?
However, the intensity of the deflected light is much greater in one image than the other. If you were to place a screen behind the slit, in one case you'd see a small bright spot directly behind the slit and in the other you'd see a larger bright spot.
 
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  • #6
I can only describe it simply as "When the waves create a more perfect semi-circle around the barrier, diffraction is considered greater (the gap being equal to the wavelength of the wave)".
 
  • #7
Nugatory said:
However, the intensity of the deflected light is much greater in one image than the other. If you were to place a screen behind the slit, in one case you'd see a small bright spot directly behind the slit and in the other you'd see a larger bright spot.

But in the second case it would not be as bright as less light (due to smaller opening) is distributed over a wider range of angles.
 
  • #8
Kaneki123 said:
If you look very closely at the two images i posted, you can see that there is the same semi-circular shape of water waves in both images...So where is this "more bending of light in greater diffraction"?

The equation for the angle, θ, of the first minimum with respect to the horizontal is sinθ = λ/w. This defines the extent of the main area of light on a screen. As you decrease w, the angle increases, i.e., more diffraction.
 
  • #9
pixel said:
But in the second case it would not be as bright as less light (due to smaller opening) is distributed over a wider range of angles.
That is true. However, the off-axis areas are still brighter than they otherwise would be, a situation which is reasonably described by the informal "more bending of the light" that OP was asking about.
 
  • #10
InfiniteEntity said:
I can only describe it simply as "When the waves create a more perfect semi-circle around the barrier, diffraction is considered greater (the gap being equal to the wavelength of the wave)".
The shape of the wave front is basically to do with the overall (radial) path length and it looks pretty circular. That doesn't change much as the slot is widened - in fact. at infinity, the wave fronts are all circular. What does change A LOT is the width of the region of maximum wave power. The wider the slot, the narrow is the region. That is what Diffraction is all about.
 
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Related to A Question about Diffraction....

1. What is diffraction?

Diffraction is a phenomenon that occurs when a wave encounters an obstacle or opening. The wave bends and spreads out in all directions beyond the obstacle or opening.

2. What causes diffraction?

Diffraction is caused by the interaction of waves with obstacles or openings. The size and shape of the obstacle or opening, as well as the wavelength of the wave, determine the degree of diffraction.

3. How does diffraction affect light and sound?

Diffraction affects light and sound in similar ways. When a light wave or sound wave encounters an obstacle or opening, it bends and spreads out in all directions. This can result in changes in the intensity and direction of the wave.

4. What are some real-life examples of diffraction?

Diffraction can be observed in everyday life. Some common examples include the diffraction of light through a small opening, such as a pinhole camera, and the diffraction of sound around a corner or through a doorway. It is also responsible for the colorful patterns seen in soap bubbles.

5. How is diffraction used in science and technology?

Diffraction is used in various fields of science and technology. In optics, it is used to create diffraction gratings which are used to separate light into its component colors. In chemistry, diffraction is used to study the structure of molecules. In engineering, diffraction is used in the design of antennas for wireless communication.

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