Diffraction is defined as the bending or flaring of light around the corners of an obstacle or aperture into the region of geometrical shadow of the obstacle. This flaring is consistent with the spreading of wavelets in the Huygens construction. Diffraction occurs for waves of all types, not just ...

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does the Fresnel approximation apply in the far field?

Most sources I've looked at treat far field diffraction and near field diffraction as separate cases, with the former using the Fraunhofer approximation and the latter the Fresnel approximation. In ...
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59 views

Is Rayleigh/Wood's anomaly simply the grazing order diffraction?

Is Rayleigh/Wood's anomaly simply the grazing order diffraction? I read some related papers but I am still confused, can I simply understand it as a surface wave propagating on the surface because of ...
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34 views

What are the exact setups to observe a wave function and its collapsed state?

I was reading this article: http://io9.com/5528321/how-smart-do-you-need-to-be-to-collapse-a-wave-function and I need some clarification on the experiment setup. My current understanding is that if ...
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2answers
48 views

Diffraction of light

If $l_1$ and $l_2$ are parallel how can they both can hit same spot? Why their difference in path length is $l_2 - l_1 = d \sin \theta$ instead of 0?
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69 views

Source of a parabolic wavefront

The Huygens-Fresnel diffraction integral has been formulated for incident spherical waves. A source of a spherical wave is kind of intuitive, since the perpendicular rays of the sphere converge into a ...
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3answers
55 views

In diffraction process, how to describe the edge in the sense of particle-wave duality?

In diffraction experiments photons show behind an edge intensity distributions in the form of fringes. It seems to be without doubt that the edge is a part of the game. My question is, how to describe ...
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116 views

Why light rays gets scattered when it enters a translucent window pane?

Consider the light source is the light post, outside the window of my house (Pic 1). When the rays from the light post enters through the window pane which is translucent gets scattered and forms a ...
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0answers
104 views

Fresnel diffraction approximation (parabolic waves)

The Huygens-Fresnel principle (Introduction to Fourier Optics, Goodman), $$ U(x,y)=\frac{z}{i\lambda}\int_\Sigma U(\xi,\eta)\frac{e^{ikr}}{r}d\xi d\eta\,, $$ where $\cos \theta=\frac{z}{r}$, shows ...
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45 views

A problem in deducing $|\psi(x)|^2 \propto \cos^2(\pi sx/\lambda z_o)$ in diffraction by two slits experiment

In Quantum Mechanics for scientists and engineers by David Miller, he explains the diffraction by two slits (page $13$) and considers a beam of electrons whose wave function is $\psi(x)= \exp(ikr)$ ...
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34 views

Determining angle of distortion in a Rhombohedral unit cell

I have a film which is rhombohedrally distorted. I would like to measure by Xray diffraction, the angle of distortion of the unit cell. I can measure the in-plane and out-of-plane lattice parameters ...
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2answers
215 views

The equation of diffraction

I have learned the equation of diffraction, which is: $$\sin \theta=\frac{\lambda}{d},$$ where $\lambda$ is the wavelength and $d$ is the gap width. So, when the gap width is closer to the ...
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66 views

Diffraction of light around an object & human perception

A wave exhibits diffraction when it encounters an obstacle that bends the wave or when it spreads after emerging from an opening. Diffraction effects are more pronounced when the size of the ...
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1answer
73 views

How to transmit light ideally through not parallel tiny holes within a metal case?

I currently try to transmit light through a tiny hole of one side of a metal case in order to receive the light on the other side of the case. The tiny holes are not parallel (see image 2). Using ...
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2answers
86 views

Refraction, diffraction or reflection of human voice

Why is possible to hear in an open space someone's voice even if he's not facing me? Is it because of refraction, diffraction or reflection of the sound wave?
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2answers
97 views

How is the virtual image reconstructed from a hologram?

To make a hologram a film is exposed to an incident plane wave and wave from the object to record the interference pattern on the film. The principle is commonly explained in a way like that in p.1212 ...
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2answers
59 views

Why array of telescope is used?

To increase the resolution of an instrument, smaller wavelength and larger aperture is desirable. It is mentioned in some textbooks that the "effective" diameter of a telescope can be increased by ...
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2answers
142 views

x-ray diffraction of crystals

In explaining x-ray diffraction of crystals, usually the approach is to consider the atoms absorb radiation and scatter it, at some angles constructive interference occur and bright spots can be ...
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0answers
132 views

Question about dark fringe in diffraction

In finding the angle for the mth dark fringe of single slit diffraction using Huygen's principle, they usually split the slit into equal portions. For example, to find the first dark fringe the slit ...
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2answers
128 views

Slit width in single-slit diffraction

In Born's Atomic physics, he makes the comment on the single slit diffraction that For diffraction patterns to show themselves, it is necessary that the width of the slit employed should be of ...
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44 views

How to design a grating coupler to produce surface plasmon-polaritons (SPPs) at a desired frequency?

Following on from this question, which I found very useful on the topic, I was wondering how you would use the equation $\beta = k sin \theta \pm \nu g$ to fabricate a grating coupler to generate SPPs ...
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3answers
625 views

Why does sound wave suffer more diffraction than light waves generally?

Why do sound waves suffer more diffraction than light waves generally ? I would like more of a logical explanation rather than mathematical .
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1answer
77 views

Bragg's interference

This may be a little of a stupid question. But I was looking at a diagram describing Bragg's Law of Diffraction. and I was like...how can an interference happen if wave beam C and wave beam C' are ...
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0answers
191 views

Is the human eye diffraction limited, or is there another limiting factor?

I know that most problems involving the human eye in my undergrad physics text book tell the student to treat the human eye as a diffraction limited system (ie to assume the only factor limiting human ...
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58 views

Deviation on the Diffraction Pattern when not perpendicular

Due to Babinet principle, Diffraction pattern of an opaque .... ( you all know ). here my opaque is my wire. So, I know that if I change the angle between beam and wire ( I mean if I don't aim the ...
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1answer
65 views

Image formation or Diffraction?

I was watching this video on the YouTube channel Veritasium. In this episode, the host shows people paper containing holes of different shapes in the middle. So there is a paper which has a hole in ...
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1answer
74 views

Diffraction Pattern when not perpendicular

In single slit diffraction, we always assume that our waves are perpendicularly aimed towards the slit. But what if we aimed our waves with different angles ( for example 60 deg)? If we send the ...
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1answer
163 views

Diffraction pattern without a slit

A few weeks ago, I aimed a laser at a wire perpendicular and interestingly, I saw the diffraction pattern, like the picture below: Why is this happening? I mean, I don't have any slits and I'm ...
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226 views

X-ray diffraction on thin film

As far as I am concerned, when we perform an X-ray diffraction experiment using a Bragg-Brentano diffractometer using the "powder method" we have that the scattering pattern depends on only one angle ...
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2answers
415 views

Huygen's principle and why can't we see atoms with light

First of all, I'd like to discuss Huygen's principle. In order to explain waves diffraction, it says that every point in a wave front behaves as a source, so the next wave front is the sum of all ...
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1answer
135 views

What is a wavelength of an EM wave physically?

This might be a silly question given I am a physics undergrad, but I was suddenly confused. Usually when EM hit a gap they diffract through the gap. But if the gap is too small, diffraction can't take ...
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1answer
67 views

Is crystal diffraction actually diffraction?

It seems like a very common model that is taught in schools for crystal diffraction is that there is an incident plane wave of light on a crystal lattice, and each atom in the lattice scatters the ...
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8answers
6k views

How to measure the diameter of a thin wire? [closed]

I'm working on a project and I need to measure the diameter of a thin bare copper wire but I don't know how. Can you please tell me a way to measure the diameter of a wire? Can you give me a way, ...
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1answer
432 views

How are lattice parameters determined from reciprocal space maps?

It seems that the papers speak of reciprocal space maps with very high praise because of its ability to study strain in epitaxial films and determine the amount of relaxation. Also one can determine ...
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0answers
46 views

What causes this pattern in the reflection of a laser on a screen? [duplicate]

When I shine a red laser behind me at a wall I see a strange reflection occurring on my laptop screen Why does this happen? The pattern on my screen occurs exactly where the laser is hitting the wall. ...
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2answers
320 views

Momentum change of a photon upon diffraction at a grating

How is the momentum change of a photon is related to the grating periodicity and diffraction order? I came across with this question while studying surface plasmon polaritons (SPPs) and how to excite ...
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2answers
144 views

Why light comes out in spherical form after passing through a slit (diffraction)?

I want to know why light comes out in spherical form when it passes through the slit? I know this is due to diffraction but how? And my second question, if there is no difference between ...
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1answer
274 views

Why water wave won't diffract or bend around a boat having a length longer than its wavelength?

I get the slit version of diffraction, with the Huygen's principle. But I don't find the same principle useful. I keep thinking that a obstacle like a boat is the same as two large slits on both ...
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3answers
393 views

Diffraction of matter waves

By considering the De Broglie wavelength of particles, we discover that matter can diffract if passed through openings with itself. This poses a variety of questions, namely Can matter waves ...
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120 views

Disadvantages of viewing a diffraction grating at larger order?

If you are using a diffraction grating as a spectrometer you are likely to use high order, because you have a better resolution (as a result of larger dispersion??). But are there any disadvantage? I ...
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1answer
94 views

Are we working in the double slit argumentation with destructive interference arguments?

Stimulating water with two long straight bars one could produce linear waves. Having the right distance between the bars and the correct frequency of the steady system we get in the middle between the ...
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71 views

Relativity - Diffraction Of Light

Following thought experiment. Inside a rocket, right in the middle, we place two lasers pointing in opposite directions. Both emitting the same wavelength. The Left wall of the rocket is L1 while ...
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260 views

I have negative slop of Williamson-Hall plot, XRD data. Is this right?

I have Ag (silver) powder sample. I measured xdd of the sample and got very good 2theta peak. Since I want to know bulk modulus and Young's modulus of Ag(silver), So, I got williamson-Hall plot ...
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1answer
54 views

Criterion for resolvability and spot size for optical systems

Look at the following table: By spot size I mean if we have a point source for the object, the angular radius of the spot created by the source as viewed in the image plane. My question is is all ...
2
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1answer
109 views

Fraunhofer Diffraction and Lenses

Suppose we have the diffraction pattern for a single slit in the Fraunhofer approximation. In order to see this diffraction patter at finite distance we locate a converging lens. Is the diffraction ...
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1answer
57 views

Path length requirement for diffraction problem [closed]

The following question has been asked in a problem sheet I have been asked to answer: "The above diagram relates to the path lengths of radiation, with an angle of incidence, θ, reflecting off ...
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1answer
84 views

Why subwavelength objects can not be seen with optical microscope?

What would happen if we would take a very small sphere around 200nm diameter and try to detect it from the most efficient optical microscope? Technically, the Rayleigh diffraction limit prevents the ...
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56 views

Trying to understand electron diffraction

I'm trying to understand how electron diffraction works, but I'm not really getting it. Here's an image Here are a couple of questions about it that I can't figure out. Why is the angle of the ...
2
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1answer
41 views

Does the Abbe limit hold for a single lens?

Let us say I have a single (converging lens) could I use the Abbe diffraction limit (for a microscope) to find its resolution or do I have to use the Rayleigh criterion. (i.e. Is the Abbe diffraction ...
4
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1answer
91 views

Beating the Diffraction Limit with NSOM

I am trying to understand exactly why we can beat the diffraction limit when using near-field scanning optical microscopy (NSOM). For those who aren't familiar with NSOM, check out this article: ...
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1answer
102 views

Do off axis sources produces the same diffraction pattern as on axis sources?

Let's say I have a simple lens and I am viewing two sources of light A and B through this lens. A is on the axis and B is not as shown in the digram below. Will A and B produce exactly the same ...