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1answer
30 views

Single slit diffraction pattern in 2D

I was looking at previous exams and I saw a question with single slit diffraction. Please look at picture on the website: http://www.physicsforums.com/showthread.php?p=4807732#post4807732 So, this ...
3
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1answer
45 views

Is that a result of thin-film interference?

Several years ago, I was laying on my bed and had a CD shaped transparent plastic disk (which was covering a 100 CD stack), basically a transparent CD. I don't know why but I took my phone and took a ...
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2answers
31 views

If outside a cylindrical solenoid exist an electrical field what does that mean to the Aharonov-Bohm Effect?

To the question "What is the electric field outside a cylindrical solenoid when inside is turned on a magnetic field" the answer is that outside exists a electric field. Does that mean that the ...
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0answers
20 views

What is the way to make a semi-transparent object to appear white? [closed]

Can an object appear opaque white to the eye but still be transparent ; i.e. pass light through (like a one-way mirror effect) In other words, is there any other way for an object to appear white, ...
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1answer
20 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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4answers
2k views

Trying to combine red, green and blue to produce white

I tried to mimic the mechanism of typical screens to produce white color out of red, green and blue. What I did is displayed the attached image on the screen, and moved far away as to let the ...
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8answers
1k views

Why does wavelength affect diffraction?

I have seen many questions of this type but I could nowhere find the answer to "why". I know this is a phenomenon which has been seen and discovered and we know it happens and how it happens. But my ...
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0answers
18 views

Bandpass of diffraction grating - exit slit width?

I'm supposed to derive a relation for the range of wavelengths that's being transmitted by a spectrometer (bandpass) in terms of the dispersion, focal length and exit slit width. Given grating is ...
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0answers
34 views

diffraction from sphere solution

I want to solve a problem of plane wave diffraction by a large sphere. There is a formula that I found from papers, but I think needs numerical solution. please help me to solve it The formula is ...
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2answers
35 views

Diffraction of electron through graphite film

"Electrons of wavelength 434 nm are directed into a thin film of graphite. Will they diffract?" Ignoring relativistic effects, I used de Brogile's relation, $p = \frac{h}{\lambda}$, to determine ...
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0answers
40 views

Fabry Perot Etalon - changing wavelength and plate distance

Given reflectivity $R = 0.75$, an etalon is used as an interference filter, transmitting light of wavelength $4.3\mu m$ at normal incidence. The full width half maximum is about $\Delta \lambda = 0.2 ...
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0answers
28 views

Quick question on convolution - Diffraction through a pair of slits

We know that the fourier transform of the amplitude function (in terms of $y$) gives you the amplitude function (in terms of $\theta$) Consider a pair of triangular slits: Fourier transform of ...
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0answers
25 views

Diffraction grating zeroth order intensity

I don't understand how the zeroth order intensity maximum works. The intensity of a transmission diffraction grating is: $$I=I_0\sin^2(β/2)/(β/2)^2\sin^2(Nγ/2)/\sin^2(γ/2)$$ Where $γ =kd\sin(θ)$, ...
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3answers
122 views

Young's Double Slit Experiment : What would happen if the “first slit” was too wide?

I was wondering what would happen to the fringe pattern displayed on the screen if the first slit (as shown in the picture), which is also known as "single slit", was made a bit wider. I read it in ...
3
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1answer
111 views

Covering centeremost slit of a N slit diffraction grating - what happens?

For an N-slit diffraction grating, the distance from a maxima to a minima at order p is given by $$\delta \theta = \frac{\lambda}{Np}$$ What happens to this width when the centremost $\frac{N}{2}$ ...
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2answers
128 views

Interesting relationship between diffraction and Heisenberg's Uncertainty Principle?

I recently came across an interesting explanation of diffraction through an aperture which does not use Huygens' Construction but instead relies on Heisenberg's Uncertainty Principle: The ...
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1answer
46 views

Crystal diffraction for waves vs particles

I thought that I understand the "Bragg's Law" understanding of crystal diffraction, but recently I read something that made me confused. I understand that if the planes in the crystal have ...
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0answers
22 views

Direct optical observation of the Arago spot: what would one see?

The Arago/Poisson spot is an excellent example of a constructive interference of diffracted light. In the traditional experimental layout, you observe projected light on the screen. The theory in this ...
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3answers
81 views

Is there an atomic level explanation for diffraction of light around opaque aperture?

It has always been a hard time understanding the phenomenon of diffraction of light around opaque objects. Hoe does it happen? Why does transparent objects do not diffract light? What quantum ...
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0answers
28 views

Optical Spectra and the Diffraction Grating

I'm doing a lab where we are identifying different gases by their diffraction spectra. This what my lab book says: Verify and calibrate your spectrometer, by measuring Hg and Ne. Measure ...
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1answer
37 views

Diffraction, wave length

I read that when we want to study the structure of a crystal we have to use an electromagnetic wave which has a wave length of approximately the distance between two consecutive atoms in the crystal. ...
177
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7answers
10k views

How does light bend around my finger tip?

When I close one eye and put the tip of my finger near my open eye, it seems as if the light from the background image bends around my finger slightly, warping the image near the edges of my blurry ...
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1answer
55 views

Why is a flower shaped diffraction occluder the best solution for controlling diffraction?

According to this TED talk by Jeremy Kasdin, Nasa is planning to spend $1bn on a "Starshade" project, where a giant flower shaped metal eclipser 20 meters wide is placed 50k kilometers in front of a ...
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1answer
124 views

Why are there interference patterns inside a diffraction envelope?

When double-slit diffraction occurs, there are interference patterns inside, say, the central diffraction maxima (or envelope). I am trying to understand how these interference fringes are created. ...
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1answer
76 views

Fraunhofer Diffraction using lenses [duplicate]

I've come across a question that I don't know how to tackle: An alternative way of observing Fraunhofer diffraction uses lenses to provide appropriate conditions. Sketch an optical configuration ...
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1answer
34 views

Calculating the distance between Detector and Double Slit

I have a little problem that is kind of confusing me at the moment. The following task: Light of the wavelength $\lambda = 500nm$ hits a double slit whose distance is $a = 30\mu m$. Each is $a = ...
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1answer
131 views

Why does diffraction depend on wavelength? [closed]

We've all heard of the diffraction of radio waves over a mountain and the diffraction of water waves through a gap, but why does this effect depend on wavelength? I'm looking for as simple answer as ...
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0answers
45 views

Fraunhofer Diffraction [closed]

A 1-dimensional aperture is illuminated by a parallel beam of light of wavelength $\lambda$ and the diffraction pattern is viewed on a distance screen. Show that the amplitude of the diffraction ...
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2answers
81 views

Huygen's principle in EM waves

In trying to understand diffraction, I keep coming across Huygen's principle as the why behind diffraction, and I think I understand the principle itself all right. However, I was hoping to find an ...
0
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1answer
75 views

Help in understanding the derivation for Fresnel Distance?

An Aperture of size $a$ illuminated by a parallel beam sends diffracted beam (the central maxima) in angular width approximately $λ/a$. Travelling a distance $z$, it aquires the width $zλ/a$ due to ...
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1answer
47 views

“backwards” Diffraction Grating with light source at maxima (1st, 2nd, nth order)?

How will a light source with a specific $\lambda$ positioned right at the nth order maximum pointing towards a diffraction grating be affected? Will it come out "directed"?
1
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1answer
80 views

Diffraction problem - How do I interpret

Here is a problem on diffraction - Diffraction pattern of single slit of width 0.5 cm is formed by a lens of focal length of 40 cm. calculate the distance between first dark and next bright fringe ...
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1answer
90 views

Distance between interference and diffraction fringes

In problems related to Interference and Diffraction fringes - I often have encountered phrases like "bright fringes 1.5 mm apart" or "distance between first bright fringe and 4th dark fringe". Fringe ...
0
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1answer
75 views

What physical phenomena underly the shape of this graph of diurnal UV index?

When I dig up a graphs of UV index versus time-of-day, most graphs are characteristically shaped like one of the plots shown here: That graph is from this site. What physical phenomena underly ...
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2answers
155 views

Can we observe diffraction even if the slit size is tending to zero?

According to Huygens principle, if we consider any point of the primary wave fronts, each point is the source of secondary disturbance. If the point size we consider tends to zero, the number of ...
3
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1answer
831 views

Relationship between slit size and wavelength in diffraction

Almost in every book on physics we can find a statement like "diffraction gets stronger when the size of the slit is comparable to the wavelength". Let's say we have a wall in a bathtub with a slit in ...
3
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2answers
331 views

White light diffraction

I have a hard time understanding why light waves of different wavelengths diffract in a different manner. According to Huygens' principle, every point on the wavefront is a source of a secondary wave. ...
3
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1answer
110 views

Why is the Fraunhoffer Pattern the Fourier transform of the slit?

Why is it that the fourier tranform of the slit (with value 1 where it's open?) gives the fraunhoffer diffraction pattern? Why are these two paired?
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2answers
154 views

What is Diffraction?

Diffraction is just light interacting with small objects, and bending, but this seems like a very imprecise definition to me. What is diffraction, actually? I was confused because there are at least ...
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2answers
241 views

Why do waves diffract?

There have already been a lot of questions on this site on diffraction but I still believe this one might be slightly different. In electromagnetic waves, diffraction and any other phenomenon of wave ...
0
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1answer
34 views

Diffraction from interatomic spacing

In diffraction from a single slit, we learn that the angular width of the central maxima, is given by $2\sin^{-1}\frac \lambda d$. For $d\approx \lambda$, the incoming wavefront should be spread to ...
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0answers
45 views

periodicity of diffraction gratings

Imagine we have a diffraction grating consisting of N slits (being N very large) with a separation of "d" from slit to slit. Now, we could regard this grating as a diffraction grating constructed by ...
0
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1answer
89 views

Diffraction of sound

The sound waves, by the virtue of it being a wave, shows diffraction and interference. But in diffraction, I learnt that if the wave is allowed to enter through a small aperture, there is a central ...
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0answers
66 views

Spreading UV light? Fresnel lenses?

I'm making a little UV exposure box and I'm looking for a way to evenly spread out the UV light. I've used Fresnel lenses to do just this in the past, but that was for visible light. But from what ...
4
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3answers
69 views

Why don't fogbows appear on clouds?

As far as I know clouds are lot of small droplets condensed in air. If droplets are large enough we see a rainbow. If they are small we see a fogbow. Although the size of the droplets are big enough ...
3
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2answers
154 views

Diffraction by a lens

The fraunhoffer treatment of circular apertures yields a diffraction pattern of circles, with the first minimum (dark ring) at an angular radius of $\theta$ where $\sin(\theta)=1.22\lambda/b$, where ...
0
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1answer
120 views

Diffraction/Bragg's law : how does $2\theta$ come about?

I'm trying to get my head around a problem (I should have checked whether I had the answer in class, the exams are coming up now and I don't know if I'll get a lecturer response over the holidays) I ...
2
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2answers
463 views

Fresnel distance and Geometrical limit

I read about the geometrical limit of wave theory. The source from where I read had a slightly different explanation to provide than here(The more rigorous answer is too complicated for me to ...
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1answer
156 views

Diffracton at the edges of an opaque object?

To understand the phenomenon of diffraction as an interference effects of several dipole oscillators (like in case of several symmetrical, not sawtooth, scratches in a diffraction grating), we ...
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2answers
122 views

How to be sure that a He-Ne laser light is monochromatic

How can I be sure that the emission of a He-Ne laser contains only one single mode of laser cavity? The only thing that I know is that if I use a diffraction grating and the light isn't ...