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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107 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
108 views

single slit diffraction - $\sin\theta=n(\lambda)/b $ or $\sin\theta = (2n+1)(\lambda)/b$

I'm getting a contradiction as follows and am not sure how to resolve it: logic 1 leads to the conclusion that the higher order minimas of single slit diffraction will be given by $b\sin\theta = n(\...
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2answers
132 views

Single Slit Diffraction

I am trying to derive the intensity variation function for a single slit diffraction. Sorry for the poor diagram... So I decided to take the amplitudes of the waves originating from the slit on the ...
4
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1answer
211 views

Diffraction and $k$-space

Regarding diffraction I am a little bit lost reading about reciprocal space and the space of $k$'s. As I understand it the Fourier relationship between a wavepacket $\Psi(\vec r,t)$ and the complex ...
5
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1answer
142 views

What´s the origin of the four rays that come out of the reflection of candlelight in our TV?

The reflection of a candlelight in our TV shows four emerging rays. The rays vary spatial and periodical and have a repeating pattern of the colours of the rainbow. The further the flame is from the ...
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43 views

Incommensurate structures and quasicrystals

I am trying to understand incommensurate structures. For that I have thought about a minimal model for which a Fourier transform can be calculated analytically. My idea was the following. Take a set ...
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0answers
23 views

Double Fraunhofer , Fourier transform to the image plane?

Consider the diagram below: I know that from Franhofer diffraction we have: $$u_f(x_f)\propto \int u_o(x_o) e^{-k\frac{x_f}{f}x_o} dx_o$$ Assuming small angles. I also know that $u_i(x_i)$ is ...
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0answers
29 views

What is the angular dispersion of an optical surface grating and why does the textbook answer seem to violate reciprocity?

The behavior of a surface grating can be described by the grating equation $m\lambda=d(\textrm{sin }\theta_i+\textrm{sin }\theta_d)$ [1] with $m$: diffraction order, $\lambda$: wavelength of the ...
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2answers
358 views

Derivation of Fresnel distance

An aperture of size $a$ illuminated by a parallel beam sends diffracted beam (the central maximum) in angular width approximately $\lambda/a$. Travelling a distance $z$, it acquires the width $z \...
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1answer
26 views

Why is the X-ray diffraction useful for studying the structure of nucleic acids?

It is well known that the double helix structure was determined by the X-ray diffraction method. But it always baffles me. DNAs are not simple crystals. They are not periodic, not at all. So how ...
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2answers
70 views

Best collimation at focal point of lens?

From geometrical optics it is clear that we get the best collimation when the object lies at the focal point of the lens. I know that this carries over into cases where diffraction happens, but have ...
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1answer
154 views

Total number of primary maxima in diffraction grating

I am trying to determine the total number of primary maxima that can be observed when light of wavelength 500 nm is incident normally on a diffraction grating, with the third-order maximum of the ...
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1answer
179 views

Path Difference Due to Angled Incident Light

If light incident on a diffraction grating makes an angle $\alpha$ with respect to the normal to the grating, show how $$m \lambda = d\sin\theta$$ becomes $$m\lambda = d[\sin(\theta - \alpha) + \sin(...
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1answer
262 views

Slit width for minimum spot size in electron slit diffraction if involving uncertainity principle

I don't believe the following is an accurate description of the physical but a homework problem to help understanding. A beam of electron of energy 0.025 eV moving along x-direction, passes ...
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1answer
257 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 ...
4
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1answer
822 views

Diffraction Pattern on LCD Screen

I was up late working with my red LED headlamp on and when I was looking at the black part of my LCD (Apple Retina Macbook Pro) screen I noticed this interesting diffraction pattern. I'm confused ...
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1answer
49 views

evidence for wavenature of particles from deBroglie wavelength [closed]

Doing a search on electron diffraction this, for example http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/davger2.html , the evidence does not look overwhelming for the significance of the deBroglie ...
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3answers
88 views

How many atoms does one need to get reliable crystal information with X ray or electron diffraction?

I know that, in theoretical derivations of X ray diffraction (XRD) or electron diffraction (ED), we always assume an infinite lattice, and, as you make the crystal smaller, edge effects start to ...
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2answers
697 views

Diffraction in Electromagnetic Waves

Diffraction can be observed in physical waves very easily, however when it comes to the diffraction of electromagnetic waves in things like the single slit experiment, I become a little confused. In ...
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0answers
83 views

Neutron diffraction on Salty Ice VII

Can someone explain in layman's term how this figure shows the presence of Cl and Li ions in Ice VII ? What can we deduce about the crystal from this data ? The whole figure and caption are ...
4
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0answers
56 views

Seeing light source from its diffracted light

Even if the line of sight is blocked by something(like a wall as in figure) will I able to see the light source if I see the diffracted light of the source? 1.Will the observer no. 2 see the light ...
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0answers
18 views

Diffractive peak for high-frequency scattering from a sphere with small index of refraction?

How does a transparent sphere's shadow fade as $n\to 1$? Consider radiation of wavenumber $k$ incident on a transparent sphere of radius $a$ and index of refraction $n$ in the limit $ka \gg 1$. (...
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1answer
39 views

Calculating wavelengths from angles in a diffraction grating? [closed]

I am having some problems calculating wavelengths from some given information about a grating spectrum. A diffraction grating with a spacing of 3μm is used in a spectrometer to investigate the ...
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0answers
64 views

Why does fluorescence emission detector pick up second order wavelengths with first order scan, even though they have different angles?

my question in more detail and with an example: Let's say I have a 980nm laser and I use that laser to excite my fluorescent solution in cuvette. My scan range is from 300 to 800nm. If, for example I ...
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1answer
4k views

Fresnel half-period zone

I am following this set of lecture notes (see below). I understand that the idea is to evaluate the Fresnel integral for the circular aperture using the graphic method. However I don't understand at ...
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1answer
24 views

Within what range of defocus from the object/image plane does the Fraunhoffer approximation hold?

The Fraunhoffer apporximation of diffraction is said to hold for an image "at infinity," or to be quantitative, for any observation point $R >> \frac{a^2}{\lambda}$. But it is said that, ...
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1answer
84 views

how can interference occur within diffraction?

My book says : The number of interference fringes occuring in the broad diffraction peak depends on the ratio d/a that is the ratio of the distance between the two slits to the width of a slit. In ...
3
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4answers
184 views

What makes the radiation behind slits coherent?

Have a look on the sketch To get such a intensity distribution of light behind a slit we presuppose that all the light that moves on the two lines is coherent; of the same wavelength AND the same ...
4
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1answer
47 views

Explain Sun Glare

Above is a picture that I took just before the sun set. Notice the prominent red blob to the left of the sun. Can anyone explain the phenomenon that creates superimposed shapes and blobs in images of ...
3
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1answer
57 views

X-ray diffraction: Is there an intuitive explanation of structure and form factors?

We have just started x-ray diffraction and I am utterly lost. We were given two formulas: First formula: The intensity of the x-rays scattered by $\mathbf{Q}=\mathbf{k}-\mathbf{k}'$ is given ...
9
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3answers
229 views

Fraunhofer diffraction contradiction

Assume two obstacles are complementary. For example, a circular aperture and a circular stop of same radii. My theoretical analysis leads to contradictory conclusions about such situations. 1) ...
3
votes
1answer
157 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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1answer
80 views

Diffraction wavelength relationship [closed]

This question appears somewhat similar to other questions asking about why wavelength affects diffraction (a concept which I'm still not 100% sure on...) however my query is different and not answered ...
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2answers
114 views

Why the incessant confusion between diffraction and interference? [closed]

Feynman said, "No one has ever been able to define the difference between interference and diffraction satisfactorily. It is just a question of usage, and there is no specific, important physical ...
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1answer
29 views

Actual spot size = geometric spot size + diffraction spot size?

I read in [1] that for a camera obscura the total spot diameter is equal to the diameter of the spot produced concerning geometric optics only plus the diameter of the spot concerning only diffraction....
2
votes
1answer
46 views

What exactly is the reciprocal lattice and how is it connected to the Ewald sphere?

I want to understand what the reciprocal lattice is and how it is connected to the Ewald sphere. I know a very similar question has been asked on this site already: Reciprocal lattices. The top ...
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4answers
689 views

Which formula for the de Broglie wavelength of an electron is correct?

So, I have my exams in physics in a week, and upon reviewing I was confused by the explanation of de Broglie wavelength of electrons in my book. Firstly, they stated that the equation was: $\lambda = \...
2
votes
1answer
40 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 ...
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0answers
29 views

Radial Distribution Function - Structure Factor relation, deriviation help

I'm attempting to prove the relation between the structure factor and the RDF, following the deriviation here (pg 92-94). The solution this source comes too disagrees with this paper which I trust ...
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0answers
21 views

What is the relationship between the size of a slit and wavelength in diffraction? [duplicate]

Almost everywhere I see the statement that diffraction gets stronger when the size of the slit is comparable to the wavelength. I would just like to know the logic behind. Could anyone help me please? ...
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2answers
70 views

Are wave fronts in double-slit experiments moving forward? [closed]

I ask a question about "What is a wavefront?" which follows the question "What makes the radiation behind a slit coherent". For the wavefront it was answered, that "In electromagnetics ...(that are) ...
1
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0answers
24 views

Why isn't every magnetic neutron scattering peak a nuclear scattering peak as well?

Neutron diffraction is a well-established technique for determining the magnetic unit cell of magnetic materials. The idea is that nuclear scattering gives you peaks that correspond to the crystal ...
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0answers
18 views

Producing a collimated beam from a point source

I have an optical fibre of numerical aperture $NA$, of very small core radius, located at the focal point ,$f$, of a lens. I should produce a collimated beam of initial radius $f\cdot NA$. But what ...
1
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1answer
28 views

Diffraction grating (finding number of emission lines)

I came across a question on isaacphysics.org where youre given information about a diffraction grating, the spacing of the gaps and the colour and location (in degrees) of 8 different maxima, of four ...
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2answers
65 views

Single slit diffraction - wave vs particle view

If monochromatic light is shot through a single slit onto a screen, we can analyze the pattern on the screen using wave properties. This analysis is done assuming the wavelength is constant. But with ...
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2answers
92 views

Can gravitational waves diffract off massive objects?

Can gravitational waves diffract off massive objects? If so, how much mass is needed to significantly disturb the waves propagation?
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4answers
911 views

Why does light diffract only through slits?

We can see diffraction of light if we allow light to pass through a slit, but why doesn't diffraction occur if we obstruct light using some other object, say a block? Why are shadows formed? Why doesn'...
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1answer
57 views

Does this shadow diffraction effect have a name?

I noticed a cool diffraction effect today as I was sitting outside in bright sunshine: Suppose you have a fixed edge casting a shadow. If you put your hand on the side of the edge nearer to the ...
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2answers
65 views

What would diffraction of a macroscopic object look like?

I read an interesting question here in the forum (Will a football (soccer) diffract?) and came up with the following doubt: even though its diffraction angle is too small to be detected, if we had the ...