The tag has no wiki summary.

learn more… | top users | synonyms

3
votes
2answers
62 views

How can shadows ever be sharp?

When I hold my hand underneath my lamp, the shadow my hand casts is crisp and sharp, meaning that the edges are well defined and not blurred. But according to Huygen's principle, shouldn't the light ...
7
votes
3answers
159 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 ...
2
votes
1answer
78 views

Fresnel lens/kinoform: How to model diffraction at the edges of zones?

I would like to find the intensity distribution of light due to the diffraction at the edges of zones on Fresnel lenses or kinoforms. (That is, location of orders, heights of maxima, etc.) I can't ...
0
votes
0answers
7 views

How to estimate the lattice parameter from a Debye-Scherrer diffractogram

The question is: In a Debye-Scherrer diffractogram, centers of maximum intensity were noted at the following angles with respect to the straight through position (all these angles are in degrees): ...
3
votes
1answer
128 views

Resolving power of a diffraction grating?

I was working thru a derivation of the resolving power of a diffraction grating at the $n$th order. Here is that derivation: Let us say we have a diffraction grating width $W$ and are looking at ...
0
votes
1answer
89 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) + ...
0
votes
0answers
5 views

How report that bragg reflection from PVC filters is greater than polypropylene filters?

I have been told that PVC filters will give a higher background in XRD analysis due to the high absorption of the Cl component. My argument is that another filter material should be used when ...
0
votes
0answers
25 views

Fringe Localisation

How am I to understand where the fringes of a given setup are localised? For example, Young's double slits have non-localised fringes, that is the fringes are localised (and so are well formed) at ...
0
votes
1answer
98 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 ...
1
vote
3answers
126 views

Can only one electron or photon produce interference pattern?

If we shoot one electron or photon at a time to a double slit for a long time, interference pattern will build up on the other side. If the gap between each electron or photon is long enough that they ...
0
votes
1answer
21 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
votes
0answers
24 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 ...
1
vote
1answer
94 views

Basic rule for diffraction

I'm a high school student. I still don't understand the reflection, diffraction and refraction of light. It seems to me that in concept of quantum physics, reflection is just a process of object ...
0
votes
1answer
24 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 ...
1
vote
3answers
98 views

Why diffraction is related to wavelength not amplitude

For diffraction, the wavelength of the incident beam should be in range magnitude of the slit length, but why the amplitude is not related to the length of the slit?
1
vote
1answer
79 views

How does a non-diffracting beam form from a converging ring of illumination?

I am trying to intuitively understand the basics of the supplementary text of a recent publication from Eric Betzig's group on lattice light sheet microscopy (1). I am confused by the explanation of ...
3
votes
1answer
3k 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 ...
1
vote
1answer
38 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 ...
2
votes
1answer
99 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 ...
2
votes
1answer
64 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 ...
0
votes
0answers
34 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 ...
1
vote
0answers
21 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 ...
3
votes
0answers
36 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: ...
101
votes
6answers
10k views

Very strange shadow phenomenon

I was laying on my bed, reading a book when the sun shone through the windows on my left. I happened to look at the wall on my right and noticed this very strange effect. The shadow of my elbow, when ...
1
vote
0answers
17 views

Diffraction from a single slit experiment and Heisenberg's uncertainty principle [duplicate]

Practically how to separated between Fraunhofer and Fresnel diffraction? Do all diffraction fringes from single slit have same peaks? Why?
1
vote
2answers
42 views

Intuitive picture of diffraction without fictitious secondary wavelet

This question has been asked in a similar way but no satisfactory answers came up. Huygen's principle relies on the fact that if we consider an aperture, every element dS on the surface of the ...
14
votes
3answers
230 views

Does the diffracted electron radiate photons?

When electron is diffracted after the slit it might follow different direction, than before the slit. That means, that going through the slit it gains some acceleration. And accelerated charge emits ...
4
votes
1answer
275 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 ...
5
votes
0answers
167 views

Why is this way of calculating the diffraction pattern valid?

I've seen that in some books (Fowles) the intensity of the diffraction pattern is calculated in the following way. We place the source $S$ and the point at the screen $P$ in the line perpendicular ...
0
votes
2answers
38 views

What should be the width of the slit in single slit diffraction experiment?

What should be the width of the slit in single slit diffraction experiment? If the wavelength is taken lambda while doing experiment.
3
votes
2answers
665 views

Perfect pinhole diffraction pattern with sharp fringes using a 632nm laser

I'm trying to produce a diffraction pattern with pinhole using a laser of 632nm wavelength .The pinholes' diameter are ranging from 10um , 25um , 50 um , 0.1mm and so on . I also have good lenses for ...
0
votes
0answers
47 views

Intensity of waves in single-slit diffraction

So I am trying to determine the relation between intensities of waves in single slit diffraction. Since I am pretty new to this topic, I couldn't find a way how to calculate the ratio between the ...
3
votes
1answer
54 views

How can diffraction happen in the Hubble Telescope?

I've seen people talking about the angular resolution of the HST is, if using Rayleigh's criterion, equal to: $$\theta = 1.220 \frac{\lambda}{D}$$ My question is, since the diameter of the HST $D$ ...
0
votes
1answer
28 views

How do I interpret the math relating to diffraction?

The following is a quote from the Haifa Lectures (Mendel Sachs) But if both slits are open, the wave function for the electron penetrating screen S1 is the superposition of states, $(\psi_1 + ...
23
votes
9answers
6k 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 ...
0
votes
2answers
22 views

What is an off-axis peak in x-ray diffractometry?

I'm looking at a $\theta$ - 2$\theta$ pattern of my thin film which in bulk is cubic (bcc) and I see 001 and 002 peaks of the film. There is supposed to be a tetragonal distortion meaning that I need ...
4
votes
4answers
97 views

Possibility of making an experiment in a classroom to simulate DNA diffraction

I am a TA in a structural chemistry class. The professor want me to show students how Watson and Crick determined the structure of DNA from X-ray diffraction results of DNA crystals. The professor ...
1
vote
0answers
31 views

Can I calculate the form of the aperture from the diffraction pattern?

As I understand, the Fraunhofer diffraction pattern of light is the Fourier transform of the aperture. More precisely, the amplitude of light would be the Fourier transform and the intensity its ...
0
votes
1answer
71 views

Diffraction grating problem [closed]

We have 8 slits, each separated from its neighbour by $ 0.05$mm. We use light of wavelength $576$nm. The problem is to calculate at what angle the first minimum occurs. The answer is given: ...
4
votes
4answers
9k views

Difference Between Fraunhofer and Fresnel Diffraction

What is the difference between Fraunhofer diffraction and Fresnel diffraction? I mean diffraction is just bending of light waves or waves in general around a point. So how can there be two types of ...
0
votes
1answer
61 views

Simulating of Fraunhofer Diffraction of Zigzags by FFT

I tried to study the diffraction pattern of the following zigzag grating by Matlab(FFT of this image).. And the result showed like this(please ignore the scale bar in this img) I think the ...
6
votes
1answer
334 views

Self-Accelerating wavepackets: What are they and can they impulse a spaceship?

Nature today published a (paywalled) article that mentions 'Self-accelerating Dirac wavepackets'. They claim that they behave in a similar fashion as the diffractive tricks of polarized beams that ...
0
votes
0answers
11 views

How do I derive Sommerfeld's solution of the case when the incident ray is aimed obliquely to the edge of the screen?

I already know that the Sommerfeld's solution to this problem is conical. But internet does not show me the simple of exact derivation of this solution. How do I solve this problem?
12
votes
2answers
337 views

Is diffraction affected by interaction between photons and electrons?

Suppose we take a sheet of ordinary metal, make a narrow slit in it, and shine a light beam through the slit onto a screen. The light beam will diffract from the edges of the slit and spread out onto ...
2
votes
3answers
98 views

Is it theoretically possible to project sound in a line, like flashlights?

I was wondering if there is a way to project sound waves on a particular point, like a laser? So that you can you can privately send a voice message to a specific person in crowd. The very first idea ...
0
votes
0answers
48 views

Huygens and philosophy of the slit

A single (narrow) slit diffraction pattern, can be explained/described classically with Huygens' principle (1678), and quantum mechanically with the Uncertainty principle. If the pattern on the screen ...
9
votes
2answers
216 views

Wavelength used in manufacturing of integrated circuits (IC)

How is it that the silicon ICs industry can burn ICs of a dozen nanometers using photolytography with UV laser of about 193 nanometers? Since the gates are smaller than the wavelength, for example ...
1
vote
0answers
90 views

Can the intensity distribution behind edges and slits be explaint by the interaction with the surface electrons of the edges?

Reading about diffraction of EM radiation on edges, slits and multi slits as well as about electron diffraction around a wire I came to the conclusion that the intensity distributions on an observers ...
2
votes
1answer
185 views

Is it possible to “focus” a radio wave to target an area much smaller than its wavelength?

Recently I was reading about a technology that uses radio waves to stimulate neurons to fire. The radio waves have the advantage of being able to pass through the skull (hence being non-invasive) but ...
2
votes
1answer
62 views

Diffracted electron - where does it gain additional momentum?

When an electron is diffracted, the momentum after the diffraction has different direction than before. Where does the electron gain this momentum? This is related to this question, but it's ...