11 votes
Accepted

Is Kirchhoff's scalar theory of diffraction mathematically inconsistent?

Kirchhoff's scalar diffraction theory is mathematically inconsistent. The reason is as follows. Kirchhoff proved that any function $U$ satisfying the homogeneous wave equation $\nabla^2U+k^2U=0$ also ...
hyportnex's user avatar
  • 18.9k
8 votes

How does Davisson and Germer experiment indicate the wave nature of electrons?

The Davisson and Germer experiment used a crystal to scatter electrons. A crystal, as used in this case, is a solid with a periodic structure. So, when the electrons impinge on the crystal and you ...
JQK's user avatar
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7 votes
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Intuitive way to understand diffraction

This answer says pretty much what Quillo said in the comment. Slightly more formally, we have Huygens's principle: Each point on a wavefront behaves like a point source of waves in its own right, ...
Philip Wood's user avatar
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7 votes
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Can you have diffraction without a slit, simply by reducing the size of light source?

In case you have in mind a point-source, then - no. By definition of diffraction (you can check it in wiki) it's light bending around obstacles corners or aperture. By definition, point-source of ...
Agnius Vasiliauskas's user avatar
6 votes
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DIY Spectrophotometer doesn't work properly in the IR range

I did some more testing, and figured out that 940nm was simply out of the range of my spectrophotometer. Looking at the scale in the software after calibration, it should work fine for wavelengths up ...
Matthew_R's user avatar
  • 321
6 votes

Intuitive way to understand diffraction

In addition to the argument using Huygens' principle, there is an argument based on the uncertainty principle. Short version: a small slit produces a large distribution of transverse wave vector ...
garyp's user avatar
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4 votes

Why do two blurry shadows, when brought close to each other, appear to "bulge" and merge?

The shadow blister effect does not depend on diffraction or nonlinearity. It only requires two shadow-casting objects at different distances from a light source that is larger than a point. The wiki ...
Rich006's user avatar
  • 689
4 votes
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Maximum numerical aperture and diffraction limit of a lens

It's about aberration. Generally, aberration increases with increasing numerical aperture, while diffraction decreases. Thus, there is a numerical aperture value below which diffraction limits the ...
John Doty's user avatar
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4 votes

Can you have diffraction without a slit, simply by reducing the size of light source?

All objects diffract and diffraction is light's interaction with obstacles, specifically with their edges. The reason we see the effect more pronounced with smaller slits/openings is because the ...
hyportnex's user avatar
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3 votes
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Physical meaning of Laue's condition for diffraction from crystals

But how can a 'particular vector' equal a set of vectors= Of course it is mathematical nonsense to say, a particular vector $\Delta\mathbf{k}$ is equal to a set of vectors. $$\Delta\mathbf{k} = \{ \...
Thomas Fritsch's user avatar
3 votes
Accepted

Uncertainty principle, maybe it doesn't forbid simultaneous measurements of position and momentum?

For the photon to resolve the hole, it has to have a wavelength smaller than the hole, which gives it a momentum on the order of the momentum uncertainty caused by the hole, defeating the purpose of a ...
JEB's user avatar
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3 votes

DIY Spectrophotometer doesn't work properly in the IR range

Best spectrums I've got: Calibration spectrum using a CFL light : 365nm UV lamp from Amazon: Rayleigh–Jeans law/blackbody radiation experiment results: I've tried a bunch of other light sources but ...
Matthew_R's user avatar
  • 321
3 votes

Diffraction of wave on an edge

First, note that diffraction on edge has an exact solution known as Sommerfeld solution. You can play with it to get a better understanding. Now, what differs here for different wavelengths is not ...
Ruslan's user avatar
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3 votes

What is the physical reasoning behind the mathematical derivation of double-slit interference pattern and single-slit diffraction pattern?

About "(...) the minima equation for double slit and single slit are opposite of each other, despite both are built on a similar concept." no one has answered yet. The answer to this ...
Radek D's user avatar
  • 95
3 votes

Is my understanding of the double-slit experiment correct?

You're doing fine. People will quibble with some of your language choices. They will point out that your way of thinking is not as useful as some other ways of thinking for one or another specific ...
WillO's user avatar
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3 votes

Why do two blurry shadows, when brought close to each other, appear to "bulge" and merge?

When I was a kid and would read about eclipses, all the talk of umbras and penumbras made my eyes glaze over a little bit, but it's a concept you really need to have if you want to understand why this ...
Mark Foskey's user avatar
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3 votes
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Why do shadows from the sun join each other when near enough?

Unfortunately, all of the highly upvoted answers to this question are wrong. One of them says that it's a diffraction effect. It's actually wholly explainable by geometric optics. The other two (John ...
benrg's user avatar
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3 votes
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What is the upper limit of size for diffracting an object?

As far as I know the largest object that has been successfully diffracted is a oligoporphyrin molecule with a molecular weight of about $25000$. This was done on 2019 and is reported in Quantum ...
John Rennie's user avatar
2 votes

Why do shadows from the sun join each other when near enough?

It's the shadow blister effect. See my answer to the same question posted more recently here.
Rich006's user avatar
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2 votes
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In single slit diffraction, why does the minima occur at integer multiples of lambda, which is contrary to double slit?

The first $0$ of the diffraction pattern of a wide slit corresponds to an angle $\theta$ such that $sin(\theta) = \lambda/a$. The path difference between the extreme rays is therefore $a sin(\theta) = ...
Vincent Fraticelli's user avatar
2 votes
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Fermat's principle of least time confusion

Path-integral-based explanations are quite different from typical dynamical physics explanations, and switching back and forth between them is quite tricky. A dynamical physics explanation starts with ...
Ken Wharton's user avatar
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2 votes

Explanation of diffraction of a single light ray by Huygens' principle

I planned a comment, but after reading the existing ones, I think a direct answer addressing the main conceptual issue could be more appropriate. There is nothing like a straight-line, one-dimensional ...
GiorgioP-DoomsdayClockIsAt-90's user avatar
2 votes

Geometrical and wave physical effects

Geometrical Optics is what can be built on the assumptions that light travels through a homogeneous medium in a straight line, and that light bends at the interface between media in accordance with ...
Philip Wood's user avatar
  • 35.7k
2 votes
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Explanation of diffraction of a single light ray by Huygens' principle

Huygens principle works when light is treated as a wave. Here, the diffraction patterns arise due to the interference of different points of the wavefront. However, when you talk about a single ray, ...
S.G's user avatar
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2 votes
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How to explain interference pattern in our eye?

Maybe I'm misunderstanding your question, but the distance $a$ doesn't matter in the sense that if you move the light source farther away, you would still look in the exact same direction to see the ...
Puk's user avatar
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2 votes

In single-slit interference, why don't we consider all combinations of points and their contribution to the diffraction pattern?

To get the pattern, it's enough to find the directions of zero intensity by the principle that any ray has a partner anihililating it. The actual form of the intensity between two zeros depends on the ...
Roland F's user avatar
2 votes
Accepted

In single-slit interference, why don't we consider all combinations of points and their contribution to the diffraction pattern?

"... we aren't considering each pair of points along the single slit ..." No, but we are considering each point, and we're choosing to add the contributions from each point in the most ...
Philip Wood's user avatar
  • 35.7k
2 votes

Interference in single slit

The slit must be at least one wavelength wide. Below $\lambda/2$ you see a point source. For an interference pattern, distinct radial lengths from points on the slit as sources to a point of ...
Roland F's user avatar
2 votes

Diffraction proof

Two nothings is nothing. Reliably. So if you can pair each little virtual source with another that causes destructive interference you can be confident that when you add up the contribution from all ...
M. Enns's user avatar
  • 8,747
1 vote

Abbe diffraction limit and Fourier

All/most of our coherent sources are also monochrome as well (i.e. lasers), but in practice incoherent sources interfere just fine .... the mix of wavelengths just creates a an overlap of patterns. ...
PhysicsDave's user avatar
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