What is Diffraction: Definition and 1000 Discussions
Diffraction refers to various phenomena that occur when a wave encounters an obstacle or opening. It is defined as the bending of waves around the corners of an obstacle or through an aperture into the region of geometrical shadow of the obstacle/aperture. The diffracting object or aperture effectively becomes a secondary source of the propagating wave. Italian scientist Francesco Maria Grimaldi coined the word diffraction and was the first to record accurate observations of the phenomenon in 1660.
In classical physics, the diffraction phenomenon is described by the Huygens–Fresnel principle that treats each point in a propagating wavefront as a collection of individual spherical wavelets. The characteristic bending pattern is most pronounced when a wave from a coherent source (such as a laser) encounters a slit/aperture that is comparable in size to its wavelength, as shown in the inserted image. This is due to the addition, or interference, of different points on the wavefront (or, equivalently, each wavelet) that travel by paths of different lengths to the registering surface. However, if there are multiple, closely spaced openings, a complex pattern of varying intensity can result.
These effects also occur when a light wave travels through a medium with a varying refractive index, or when a sound wave travels through a medium with varying acoustic impedance – all waves diffract, including gravitational waves, water waves, and other electromagnetic waves such as X-rays and radio waves. Furthermore, quantum mechanics also demonstrates that matter possesses wave-like properties, and hence, undergoes diffraction (which is measurable at subatomic to molecular levels).
Homework Statement
I have an issue for a question I have. The problem is that I need to find the distance between the slits of a diffraction grating. Normally this would be pretty simple, but I'm not given the wavelength of the light source we're supposed to use to find it out.
Homework...
Homework Statement
A narrow beam of collimated white light falls at normal incidence upon a transmission grating with 3150 lines per cm. A spectrum is formed by the grating on a screen 30 cm away. If a 1 cm square hole is cut in the screen its inner edge being 5 cm from the zeroth order...
Homework Statement
Monochromatic light illuminates a diffraction grating having 5950 lines/cm. The diffraction angle for the first order image is 18 degrees. what is the wavelength in nm
Homework Equations
wavelength=D * Sin(Theta
The Attempt at a Solution
So I know theta is...
Homework Statement
Light of wavelength 676 nm in vacuum is incident on a single slit whose width is 1.60 × 10-5 m. The setup is then immersed in water whose index of refraction is 1.33. What is the angle θ that locates the third dark fringe with respect to the central bright fringe?Homework...
ok, i did a lab and found values of the diameter of the electron rings after diffraction from a graphite. i also have the voltage that i accelerate the electrons to hit the graphite.
so to find the distance between adjacent planes of graphite carbon "d", we use bragg's diffraction law right...
What's the difference when I observe the emission lines of say, Hydrogen or Neon, on two diffraction gratings having different line spacings? Will there be colors that will only be observed in one and not the other? Thank you!
Homework Statement
The figure shows the interference pattern on a screen 1.0 m behind a diffraction grating. The wavelength of the light is 600 nm. How many lines per millimeter does the grating have?
Homework Equations
lines/mm = 1/ distance between slits
The Attempt at a...
Homework Statement
A collimated laser beam ( λ=600 nm) having an intensity I=10 W/m2 is incident
perpendicularly on an opaque screen containing a circular hole with diameter
D=3.6 mm. Calculate the intensity at a point on the central axis that is distanced
180 cm from the screen.Homework...
Hi there!
I wonder if anyone could explain to me exactly how the optics of Luneburg lenses work? Are there any major losses due to diffraction, spill-over etc? Is it possible to focus just one image using this lens?
Thanks,
Jean
Homework Statement
It is question number 1a here:
http://web.utk.edu/~tbarnes/website/cm/cm_hw/hw4/cm_hw4.pdf
The Attempt at a Solution
I'm not entirely sure how to go about this. I've rearranged this equation to get
-3ln(0.33)=Ghkl2<\delta^2>The thing that confuses me is that Ghkl2 is a...
Homework Statement
I have a spectroscope that looks like this:
Mercury/Helium lamp --> Split --> Lens --> Diffraction grating --> Lens --> Ocular
I want to measure the grating spacing d with this setup.
Homework Equations
d \sin{\theta} = m \lambda
The Attempt at a Solution
Can...
It is quite typical example for a text to mention Airy disc (a diffraction patten for a circular aperture), also in wiki http://en.wikipedia.org/wiki/Airy_disc. But what wiki confusing me is , in the mathematical details section, the intensity is given by J1(x)/x, where J1 is the first order...
Hi,
I am a bit confused regarding using FFT to calculate the 1D single slit diffraction pattern.. Let's take the simple setup shown here:
http://electron9.phys.utk.edu/optics421/modules/m6/images/sslit.gif"
If I wanted to do a quick calculation using Matlab, I would create a 1xN matrix...
Homework Statement
You need to use your cell phone which broadcasts an 830 MHz signal but you're in an alley between two massive radio wave absorbing building that have only a 15m space between them. What is the angular width in degrees of the electromagnetic wave after it emerges from between...
Homework Statement
An X Ray beam (wavelength 10^10m) is incident upon a sample of a powdered crystalline material. At a distance of 5m from the sample a flat detecting film has been placed. A pattern of 2 circles have been recorded on this film (radius 2cm and 3.5cm).
What crystal spacing...
2 plane waves do 1 slit diffraction, one comes perpendicularly to the slit, the other with an angle theta.
Rayleigh criterion says that in order to distinguish between them one's primary maximum must be further than the other wave's first minimum, therefore (after calculating and getting that...
In my Physics lab, I'm doing X-Ray diffraction and attempting to determine the crystal structure of some common salts. To do this, I first need to determine the Miller Indices for the crystal structures that I'm considering. I can then match the location of peaks in X-Ray data (we're using...
Homework Statement
Hi guys, so here's a bonus question on my assignment for materials course.
" A metallic crystal is irradiated with Xrays of a fixed wavelength. Bragg reflection is observed at angles of 23 and 73.5 degrees, as well as another angle phi which is intermediate between the...
I'm doing a project which involves the need to find the diffraction pattern of the sodium d lines from a sodium lamp using a telescope (focal point 3.39m) and a lens that causes the light 'rays' that hit the diffraction grating to be parallel to each other.
the diffraction grating follows the...
Homework Statement
Light with wavelengths of 520 nm and 630 nm passes through a diffraction grating containing 6000 lines/cm.
a. Sketch a diagram of the image produced from m=0 to m=2, labeling the order of each fringe.
b. Calculate the angles for the first and second order maxima that...
Homework Statement
A monochromatic light source is incident normally on a diffraction grating with 600 lines per mm. The beam passes through the grating and the fringes are observed on a screen 5m away. The apparatus is then immersed in a liquid whose refractive index is 1.3. In consequence...
Homework Statement
A parallel beam of mono-chromatic light (500nm) is incident on 2 long narrow slits: slit width is 0.1mm and the distance between slit centres is 0.3mm.
a) How many bright fringes cover the central diffraction maximum?
Homework Equations
Condition for constructive...
Hi
At night when you watch moon in cloudy weather you will see the diffraction of moon light around it in circle form and so the colorful circles . Please explaine me the physics of it.
Thancks.
Hi
At night when you watch moon in cloudy weather you will see the diffraction of moon light around it in circle form and so the colorful circles . Please explaine me the physics of it.
Thancks.
I need some help in understanding the effect of change in intensity of the central maxima in respect of a single slit illuminated by monochromatic light when:
(a) the width of the slit is increased / decreased
(b) the distance of the screen from the slit is increased / decreased
(c) the...
I'm wanting to get another optics book. I'm interested in finding a book that gives insight into how light waves interact with surfaces such as in reflection and x-ray diffraction and things like that using sufficient diagrams of the wavefronts and particles and rayleigh scattering. I want to...
Ive been marked wrong but not sure why:
The distance between the first and fifth minima of a single-slit diffraction pattern is 0.400 mm with the screen 41.0 cm away from the slit, when light of wavelength 570 nm is used. Find the slit width.
y=m(theata)D/a
m-order = 5
D-distance...
Hi Everyone,
I am having trouble with my Fourier optics. I am trying to simulate Fresnel diffraction using the following form of the equations:
Li(xi, yi) = K * magnitude ( FT{ P(xp, yp)E(xp, yp) } p= xi/ld ;q= yi/ld ) ^2
K = 1/(ld)^2
E(xp, yp) = e^(i*(PI/ld)*(xp^2+yp^2))
P is the...
that demonstrate the photon as a wave? There are tons of demonstrations showing light as a particle. Heck, even if we send it through one photon at a time, diffraction demonstrates photons as particles!
Where is the photon a wave?
1. Go to http://www.matter.org.uk/schools/Content/Interference/gratingExplored.html .
Q1. What is the effect of varying the Wavelength of the light?
The attempt at a solution. The smaller the wavelength, the lesser the degree of diffraction, as evidenced by the narrower intensity envelope...
Hello!
Recently, I'm always thinking about why diffraction effects are generally most pronounced for the size of the diffracting objectsis that is on the order of the wavelength. How about a relatively bigger object?
I try to find it everywhere I can but failed. So anyone can help? Thanks!
Homework Statement
Light of wavelength 680 nm is incident normally on a diffraction grating. Two adjacent maxima occur at angles given by sin θ = 0.2 and sin θ = 0.3, respectively. The fourth-order maxima are missing.
Slit separation d = 6.8 µm
Slit width a = 1.7 µm
What are the...
Homework Statement
Assume that the limits of the visible spectrum are arbitrarily chosen as 430 and 680 nm. Calculate the number of rulings per millimeter of a grating that will spread the first-order spectrum through an angle of 20.0 degrees.
Homework Equations
(y is lambda)
dsinø =...
Homework Statement
A line corresponding to light of the wavelength 519.8 nm is observed at an angle 12 degrees in the second-order spectrum of a diffraction grating. The grating is 1 cm in width,
what is the line spacing of the grating?
how many per centimetre?
what is the lowest order...
Hi, I started a new assignment, the last one for my course and its hard as !@#@.
I don't know how to start these questions at all if anyone can give some guidance or formulas which can be used that would be great!
http://img11.imageshack.us/img11/9773/53830806.png
Homework Statement
Light of wavelength 680 nm is incident normally on a diffraction grating. Two adjacent maxima occur at angles given by sin θ = 0.2 and sin θ = 0.3, respectively. The fourth-order maxima are missing.
(b) What is the smallest slit width this grating can have?Homework...
Is the Fresnel-Kirchhoff formula (FKF) valid also for gaussian beams? I a book starting from the gaussian intensity:
U_0(x,y)=\sqrt{\frac{2}{\pi\omega_0^2}}\exp\left(-\frac{t^2+s^2}{\omega_0^2}\right)
it said that using the FKF in free space the gaussian beam spreads (in far-field assumption)...
Optics Q!: Diffraction Pattern from a Ronchi Ruling
Hey everyone,
allow me to explain the experiment I'm working on before I get into my question. The experiment has light passing through a slit at the focal point of a lens. Since the light is at the focal point, theoretically it should...
The mechanism by which light diffracts through a two-slit experiment is alledgedly due to the superposition of a single photon at the two-slit interface, causing the photon to either constructively or destructively interfere with itself.
If this is the case, then can you please explain the...
Homework Statement
White light containing wavelengths from 396 nm to 756 nm falls on a grating with 7300 lines/cm. How wide is the first-order spectrum on a screen 2.15 m away?
Homework Equations
y=m*L*wavelenth/(d)
The Attempt at a Solution
using the equation I have found y1 to...
I'm doing a lab report on diffraction and interference. I've done several diffraction experiments (single slit, double slit, diffraction grating, Fresnel Biprism) to find the wavelength of the laser used. with Fresnel Biprism, wouldn't the refraction within the prism cause a change in...
erm anyone knows why for destructive interference to occur for a fraunhofer's diffraction pattern, the equation is a/2sin(theta) = m(lamda)/2 , ==> sin(theta) = m(lamda)/a ?
where a = slit width
lamda = wavelength
theta = angle the ray makes with the central axis
the problem i have...
Homework Statement
The sun is 45 [deg] above the horizon.
A wall, 10 [m] height is penpandicular to the line sun-earth. Compute the luminous flux, under the following conditions:
1. The geometric shadow, while the sun angular dimension is 0.5 [deg].
2. Fernsel diffraction- the sun as a...
Hello,
I would be grateful if someone could comment on my problem.
I am trying to simulate diffraction of optical wavelength on a sub-wavelength aperture (aperture diameter/wavelength < 0.1).
What I want to achieve is:
- simulate a geometrical model with an aperture of 15um diameter
-...
Homework Statement
1.compute the diffraction pattern through a ring aparture, internal radius a, external radius b, wave length lambda. the incoming wave is a monochromatic, plane wave, vertical to the ring plane.
2.how will the diffraction expression change when a->b?
3.near the aparture...
Homework Statement
Basically there's a question that I'm doing which asks me to show how to derive:
n lambda=d sin theta
We haven't learned it yet and so how do you do it?
Homework Equations
n lambda=d sin theta
The Attempt at a Solution
Not a clue!
Thanks!
When a photon diffracts through a slit, how long does it take to reach the farthest point of the diffraction pattern once it leaves the source? Would be it be the same as the time it takes to get from the source to the slit, plus to get from the slit to farthest point of light on the far wall...
Hello,
I need to calculate diffraction picture produced by source generating partially coherent illumination. I read Born and Wolf, Goodman and still I do not have complete understanding.
Suppose we have source with size d, simple object (let's take opaque rectangle) and detector. According...
In my Solid State course we've reached the topic of crystal diffraction and reciprocal lattices. I haven't had any problems so far, but I've hit a little snag in understanding how the diffraction condition 2\vec{k} \cdot \vec{G}=G^2 is equivalent to the Bragg law 2d\sin{\theta}=n\lambda.
In...