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).
I find problems on Bragg diffraction frustrating. I can't tell how the angles are defined, nor the "planes" in the crystal--they look arbitrary. Why can't I just draw a slash through the crystal at any angle I want and get diffraction off the angles I hit with the slash? Is it just that the...
Homework Statement There is an extensive source (since it isn't important it can be monochromatic). The waves goes through a condenser lens that makes them converge. So, what we have is the "image" reproduced at the other side of the lens, at the focal plane.
So now: I understand that each dot...
This is not really a homework question but a more general plea for an explenation from someone! :)
In x-ray diffraction, you get a graph with different peaks that are particular to the composition of your sample. But, why are some peaks are of higher intesities then others? What is it about...
Why do waves spread out after emerging from a narrow (\leq\lambda) opening?
Also, why do waves change direction at boundaries between regions where the wave speed differs?
I have tried to find answers to these questions by searching on the Net, but with no luck.:-(
Quick question (hopefully)
Diffraction is often classically described as light bending around corners, Huygen’s Principle treats each point of an advancing wavefront as a new source.
My grad physics professor has mummbled one time that diffraction occurs due to the interaction of light...
1. Light of wavelength 632.8nm is normally incident upon a grating of 5000 lines/cm. How many different diffraction orders can be seen in transmission?
2. m(lambda)=d(sintheta)
3. According to my text, d=1/5000lines/cm = 2x10^-6m
and sintheta= lambda/d = 632.8x10^-9/ 2x10^6 =...
Circular Diffraction Patterns HELP!
Homework Statement
Homework Equations
theata_1=1.22(lambda)(L)/D L distance from screen, D diameter of slit
w=2.44(lambda)(L)/D
The Attempt at a Solution
so this is what i did not sure where i went wrong maybe at rounding off...
Homework Statement
First I have one general question about single-slit diffraction patterns. I've never fully understood this phenomenon. In my book it is stated that there will be minima when the waves from the top and the bottom of the slit differ exactly a whole wavelength, because one...
Hi guys,
My research project involves a paraboloidal telescope with a primary diameter of 25 meters, and a focal length of 10 meters. My goal is to come up with the mathematics and numerics to determine the surface profile error of the primary mirror. We will take a point source of 2mm...
Actually, I'm studying for my entrance exams to college.
I think the professor made a mistake.
So , the question says :
A diffraction pattern of a light beam from a narrow slit and from a thread are :
a)Completely identical
b)Totally different
c)Identical except for the center.
He...
Homework Statement
Monochromatic light of wavelength 441 nm falls on a narrow slit. on a screen 2.16m away, the distance between the second minimum and the central maximum is 1.62 cm. a) calculate the angle of diffraction thetta of the second minimum. b) find the width of the slit? Rensick...
If you think of a sphereical symmetric diffraction ring, the intensity is constant for each sphereical section (intensity doesn't vary for theta or phi), but it varies kind of like a sine wave in the r dimension from zero to zero with a maximum in the middle of the ring. So that if you think...
So when they make a hologram they use a laser and it gets shot out and goes through a beam splitter and the one beam bounces off a mirror and then the object they want to make the hologram of , and the other beam bounces off a mirror and when the two beams meet they interfere and then hit the...
Do 3d glasses use diffraction to work , because the ones i read about did not say anything about diffraction , but i shed a laser through my 3d glasses and it diffracted it perfectly on the wall , it had a center bright spot and then equally spaced dots from the center out .
It seems like an interaction constrains the wave and creates a diffraction pattern that spreads through space and the rings of the diffraction pattern can likewise be constrained and create their own diffraction patterns.
Homework Statement
I'm really struggling with this one.
"A diffraction grating with 600 lines/mm is illuminated with light of wavelength 500 nm. A very wide viewing screen is 2.0 m behind the grating."
a) What is the distance between the two m=1 fringes?
b) How many bright fringes can...
I am interested to know why in any description of electron diffraction apparatus they seem to suggest that the electrons need accelerating up to 5kV (or at least several kV) to show the electron diffraction rings, this seems to give a de Broglie wavelength of around 1.2 x 10^-11m whereas the...
Reading the derivation for the single slit diffraction minima formula from this site, I'm not convinced about its argument.
http://www.math.ubc.ca/~cass/courses/m309-03a/m309-projects/krzak/index.html"
What I'm having trouble understanding is the explanation of the formula for minima when m>1...
Homework Statement
Hi guys,
I'm going through a rough time understanding double and single slit and diffraction.
Here's the first problem:
A) A single slit gives destructive interference when m*L=w*sin(theta). A double slit gives constructive interference when m*L=d*sin(theta). Explain...
Homework Statement
In lab, I obtained a single slit diffraction pattern and recorded an image of it. The slit width is known to be 0.000134 m. We are supposed to compare our experimentally-obtained diffraction pattern to the result of taking a Discrete Fourier Transform of the aperture in...
Homework Statement
A grating having 1000 lines per mm is illuminated with sodium light of mean wavelength 589.3 nm. Determine the maximum order of diffraction that can be observed.
Homework Equations
dsin(\theta)=m\lambda
d=slit spacing
The Attempt at a Solution
The order of diffraction...
Homework Statement
Show that the maximum intensity for a diffraction grating of N slits at the first principal maximum is N^2 times bigger than for a single slit.
Homework Equations
I=I(0)[sin^2(NB)/sin^2(B)] where B is (\pidsin\phi)/\lambda
The Attempt at a Solution
I feel i...
I read an introductory text about diffraction of X-rays in crystals and I am not sure why the wavelength in the crystal is assumed to be identical to the wavelength outside the crystal. I think that the speed of electromagnetic waves can depend on the type of matter, so wavelenghts can be...
Is the formula for single slit diffraction Dsin\theta = m\lambda identical to the double slit diffraction besides m being minima rather than maxima? More specifically will m + 1/2 tell me the angles between maxima?
If i shot a red laser through the top slit and microwave laser through the bottom slit
what would we expect to see in the diffraction pattern would we see a double slit pattern or a single slit pattern , how would the microwaves interfere with the red photons ,
Or if this is too...
Homework Statement
There are at least two different situations. If you have N-2 middle minimums, the amount of slits is N. Please, see the bottom left http://scienceworld.wolfram.com/physics/DiffractionGrating.html" . The case with no such thing is the question about. How can I determine the...
Hello,
I'm pondering on why bending occurs most when the width of the aperture is close to the wavelength of the propagating wave. According to Huygen's principle, should'nt there be point sources around the edges of an aperture regardless of the width and thus the bending propagate to...
Homework Statement
A diffraction grating has slit width 0.83 micrometres. When light of 430 nanometres is used, diffracted beams are observed at 14 degrees 55 minutes and at 50 degrees 40 minutes to the zero order. The first beam is assumed to be the first order and the other one can be...
Homework Statement
Light with two wavelengths (510.0 nm and 525.6 nm) is spread by a diffraction grating. On a screen 4 meters behind the grating we observe that the diffrence between the two second order maximum is 1 cm. What is the grating constant (d) ?Homework Equations
I think i only need...
Homework Statement
You have been asked to measure the width of a slit in a piece of paper. You mount the paper 80.0 centimeters from a screen and illuminate it from behind with laser light of wavelength 633 nanometers (in air). You mark two of the intensity minima as shown in the figure, and...
For this question I am considering a slit diffraction experiment set up as follows:
{Monochromatic source} ------> {Single slit} ------> {Diffraction grating with N slits} ------> {Screen with small movable detector}
The monochromatic light source emits photons one at a time. The principal...
Hi everyone. I need help comprehending single slit diffraction. I am using the textbook: College Physics by Serway / Vuille 8th Edition. This is what it says:
"To analyze the diffraction pattern, it's convenient to divide the slit into halves, as in Figure 24.17 (picture below). All the waves...
Homework Statement
Waves with small wavelengths diffract less than those with longer wavelengths. Use this information to suggest why ultrasound is much better than ordinary waves for finding the depth of the sea [3 marks]
Homework Equations
NONEThe Attempt at a Solution
Ultrasound has a...
Homework Statement
Light from a laboratory sodium lamp has two strong yellow components at 589.5923 nm and 588.9953 nm. How far apart in the first-order spectrum will these two lines be on a screen 1.00 m from a grating having 10,000 lines per centimeter?
Homework Equations
Grating...
Homework Statement
What is the maximum slit width so that no visible light exhibits a diffraction minimum?(Visible light has wavelengths from 400 nm to 750 nm.)
Homework Equations
D*sin(theta)=m*lambda ; where D = slit width,theta in degrees, m =1,2,3,..., and lambda is wavelength...
Homework Statement
The diffraction pattern shown in the figure is produced by passing He-Ne laser light (λ = 632.8 nm) through a single slit and viewing the pattern on a screen 1.58 m behind the slit.
What is the slit width?
Homework Equations
a = {(wavelength)D}/(distance of...
Homework Statement
A point source of monochromatic light (500 nm) is 50 cm from an aperture plane. The detection point is located 50 cm on the other side of the aperture plane.
a) The transmitting portion of the aperture plane is an annular ring of inner radius .5 mm and outer radius .935...
Homework Statement
First-order Bragg diffraction is observed at 25.9degrees relative to the crystal surface, with spacing between atoms of 0.26 nm.
a)What is the wavelength of the X-rays?
b)At what angle will second order be observed?
Homework Equations
m\lambda=2dsin\phi
The...
Homework Statement
Is there a good way to do a fit. The fft looks simple:
I am trying to fit data from my experiment to the very nonlinear nested sine function given as equation 3 here:
http://www.physics.umd.edu/courses/Phys375/HillSpring10/Labs/Lab5Diffraction.pdf
Homework...
Homework Statement
Typical AM radio waves usually have a frequency between 540 kHz and 1400 kHz. FM radio waves tend to have frequencies between 89 MHz and 105 MHz. Both types of waves travel at the speed of light. In terms of diffraction, use this information to help explain why in many low...
In the following I am always talking about fraunhoffer diffraction
suppose you have two slits in a doulbe slit diffraction experiment which are both exposed to the same plane wave (say the same laser) as the original source of radiation. Usually, we expect that both slits will act as EQUAL...
hey quick question about Fraunhoffer diffraction:
RESTULT 1
for a rectanguar apperture, we have the following equation for irradiance I:
I = I(0)(sin(B)/B)^2(sin(A)/A)^2 = I(0)[sinc(B)]^2[sinc(A)]^2
where, B = bu/2; A =...
I've never understood how diffraction is possible, which has led me to mistrust a good deal of quantum physics. I'm mystified as to how light starts spreading out in all directions after passing through an aperture. Supposedly it's because light spreads out like a wave, but then how is it...
Homework Statement
Okay so, I was hoping someone out there might be able to assist me with a Mineralogy problem I have. The concept is based around X-Ray Diffraction.
The question:
Derive a diffraction equation from the illustration below that relates the reflection angle (theta) to the...
Hi,
I’ve got a general question about wave-particle duality, and the experiments done with slits.
When a laser is beamed through a small slit, we get a diffraction pattern. This pattern is interesting because it contains dark bands.
When it comes to explaining the existence of...
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...