What is Diffraction grating: Definition and 202 Discussions

In optics, a diffraction grating is an optical component with a periodic structure that splits and diffracts light into several beams travelling in different directions. The emerging coloration is a form of structural coloration. The directions of these beams depend on the spacing of the grating and the wavelength of the light so that the grating acts as the dispersive element. Because of this, gratings are commonly used in monochromators and spectrometers.
For practical applications, gratings generally have ridges or rulings on their surface rather than dark lines. Such gratings can be either transmissive or reflective. Gratings that modulate the phase rather than the amplitude of the incident light are also produced, frequently using holography.The principles of diffraction gratings were discovered by James Gregory, about a year after Isaac Newton's prism experiments, initially with items such as bird feathers. The first man-made diffraction grating was made around 1785 by Philadelphia inventor David Rittenhouse, who strung hairs between two finely threaded screws. This was similar to notable German physicist Joseph von Fraunhofer's wire diffraction grating in 1821. Gratings with the lowest line-distance (d) were created, in the 1860s, by Friedrich Adolph Nobert (1806–1881) in Greifswald; then the two Americans Lewis Morris Rutherfurd (1816–1892) and William B. Rogers (1804–1882) took over the lead; and, by the end of the 19th century, the concave gratings of Henry Augustus Rowland (1848–1901) were the best available.Diffraction can create "rainbow" colors when illuminated by a wide-spectrum (e.g., continuous) light source. The sparkling effects from the closely spaced narrow tracks on optical storage disks such as CDs or DVDs are an example. Similar rainbow effects seen in thin layers of oil (or gasoline, etc.) on water are not caused by a grating but rather by iridescence in reflections from the closely spaced transmissive layers. A grating has parallel lines, while a CD has a spiral of finely spaced data tracks. Diffraction colors also appear when one looks at a bright point source through a translucent fine-pitch umbrella-fabric covering. Decorative patterned plastic films based on reflective grating patches are very inexpensive and commonplace.

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  1. L

    Number of bright fringes given by diffraction grating on a screen

    (1) In the book I am using the separation of bright fringes is indicated as being ##\Delta y=\frac{\lambda}{d}##, where ##d## is the separation of the slits so on a screen of width ##W## I would see ##\frac{W}{\frac{\lambda}{\frac{1}{N}}}## bright fringes. I don't see why the text of the...
  2. warhammer

    Question on Resolving Power of Diffraction Grating

    I have doubts about my work for the second part of the question, where I am asked if resolution will be possible or not. For the first part, I calculated No. of lines N=6.43*10^2 lines/cm For the second part, I have attached below a snapshot of my neatly written work. I request a PF member to...
  3. LCSphysicist

    Calculating the Number of Lines for a Diffraction Grating

    A spectral line of wavelength λ = 4,750˚A is actually a doublet, of separation between the lanes 0, 043˚A . a) which is the smallest number of lines a diffraction grating needs to have to separate this doublet in the 2nd order spectrum? To be honest, i don't know what to do. I first thought...
  4. P

    Problem on Diffraction Grating and Laser Crystallography

    First question: When shining a laser (##\lambda = 630nm##) through a 2D crystal, diffraction patterns are observed. Why? Possible reasons: 1. Atoms and the space between them act as diffraction gratings. 2. Bragg Diffraction, although in this case the pattern would be observed on the same...
  5. Adams2020

    The sources of error in a diffraction grating experiment

    In a diffraction grating experiment, what can be the sources of error and also what effect do these sources have on the unknown quantity (wavelength) in the experiment?
  6. H

    A diffraction grating formed by parallel adjacent tracks on a CDROM

    (d)sin(40.6)=(475*10^-9)(1) d=730*10^-9 (m) prof says answer is 1460*10^-9 (m) tho
  7. ChrisXenon

    Photographing diffraction grating interference patterns

    If I direct a laser pointer onto a diffraction grating and place a screen beyond it, I see a diffraction pattern - a line of dots - as expected. If I move the screen further away from the grating, the distance between the dots increases - again as expected. If I place a camera where the screen...
  8. ChrisXenon

    Is the diffraction grating formula wrong?

    So, two wave fronts leave adjacent "slits" in a grating and head for a screem When they get to a point of local maximum, they will have interfered constructively, and so they must be in phase. Therefore the path different will be a whole multiple of the wavelenth. People routinely draw a right...
  9. K

    Measuring the Distance between the Fringes of a Diffraction Grating

    I have been preparing for a physics practical on diffraction. More specifically, we will use a CD as a transmission grating (by peeling off the reflective layer), and measure the distance between the fringes for a specific distance between the CD and the viewing wall. However, it is unclear...
  10. K

    Diffraction Grating: Possible variables for Experiment

    For my High School Physics course, I have been tasked to design an experiment investigating the properties of a CD diffraction grating, and we MUST make a graph. Unfortunately, we only have two lasers of different wavelength, so changing the wavelength and measuring ##theta## would be a bad...
  11. K

    Do Multiple Diffraction Gratings Affect Interference Patterns?

    Here is my thinking: Let's replace the second diffraction grating with a screen. Then, after passing through the first grating, I would expect there to be an interference pattern on the screen. Depending on the distances between the first grating and second, I could have several difference...
  12. Charles Link

    Learn the Fundamentals of the Diffraction Grating Spectrometer

    Continue reading...
  13. DariusP

    Varying thickness diffraction grating

    I know that a plane wave going through a slit becomes a spherical wave because of a Huygens-Fresnel principle. Can someone explain to me why a plane wave splits into many plane waves with different directions when going through a plate with varying thickness? Can someone explain me this image?
  14. Beth N

    Diffraction Grating Vs Double-Slit: Small angle Approx.

    Homework Statement In double slit interference , the angle between the center bright fringe and the path length (aka the angle used to find the path length difference) can be approximate as a small angle. However, we cannot assume the angles of bright fringes due to diffraction gratings are...
  15. NihalRi

    Angle relationships of a blazed diffraction grating

    I am trying to understand how a blazed diffraction grating works and came across a deduction I don't understand. I believe that you don't need to know much about optics to answer this question as it is more geometry related. I have the diagram below of a diffraction grating with all the relevant...
  16. ephphatha16

    Find λ of light using a laser beam and a diffraction grating

    1. What is the advantage of using class 2 laser light? I would really appreciate if reference source is also given!Homework Equations Not needed.[/B]The Attempt at a Solution Well, I thought that using monochromatic light would made it easier to measure the distance between fringes. And also...
  17. M

    Diffraction Grating - Calculating Ruling Width

    Homework Statement The Attempt at a Solution Hi All! This is probably going to have a very simple answer. I'm stuck on question (b)(ii). The only equation I can find with the ruling width in it is the one shown and I can't find a way to calculate is as I don't know Beta. Thanks
  18. A

    A level physics doubt about a Diffraction grating

    Homework Statement Monochromatic light of wavelength 690nm passes through a diffraction grating with 300 lines per mm, producing a series of maxima on a screen. What is the greatest number of maximas that can be observed? A) 4 B) 5 C) 8 D) 9 Homework Equations n*wavelength = d*sin x The...
  19. I

    What is the wavelength difference based on a mini spectrom.?

    Homework Statement I'm a bit stuck on how to approach this problem. A miniature spectrometer used for chemical analysis has a diffraction grating with 800 slits/mm set 25.0 mm in front of the detector "screen." The detector can barely distinguish two bright lines that are 30 μm apart in the...
  20. Paddyster

    How does the diffraction grating in Canadian currency work?

    Hi, This is my first post so apologies if I'm not clear enough or if I am posting in the wrong place. I am doing my 3rd year project at university and I am creating diffraction gratings. My supervisor shown me a Canadian note and if you shine a laser through the maple leaf it will shine on the...
  21. C

    More slits, farther maxima of interference patterns, why?

    When observing interference patterns, one will notice that the maxima from a double slit are more intense and farther apart than the maxima of a single slit. Likewise, the maxima from a diffraction grating are more intense and farther apart than maxima of a double slit. Why is this? I...
  22. A

    Single Slit and Diffraction Grating Formulas

    Hi everyone. I am having some difficulty understanding the formulas of single slit diffraction and diffraction gratings. This is partly because the formulas that I have been given in class do not reflect what I have found online entirely. As we know, the formula for single slit destructive...
  23. A

    Diffraction Grating and White Light Problem

    Homework Statement White light containing wavelengths from 400 nm to 750 nm falls on a grating with 6000 lines/cm. How wide is the first-order spectrum on a screen 2.0 meters away Homework Equations dsinθ=mλ for constructive interference dsinθ=(m+1/2)λ for destructive interference Δx = λL/d...
  24. T

    Maximum frequency if there is to be one diffraction order

    Homework Statement A naval towed-array sonar comprises a line of ##80## transducers, equally spaced over a total length of ##120 m##, that is towed behind a ship so that it lies in a straight line just below the surface of the water. An adjustable phase delay can be introduced electronically...
  25. S

    Fraunhofer diffraction experiment- neural density filters

    I'm currently carrying out an experiment with Fraunhofer diffraction. It involves shining a laser beam through neural density filters, a lens and a diffraction grating, to create a diffraction pattern which is then picked up with a CCD camera, to find the intensity of the maximal peaks. However...
  26. L

    Maxima in a diffraction grating

    Homework Statement A diffraction grating is made up of slits of width 300 nm with separation 900 nm. The grating is illuminated by monochromatic plane waves of wavelength l 600 nm at normal incidence. How many maxima are there in the full diffraction pattern? Homework Equations mλ = dsinθ The...
  27. Z

    Investigation about the emission spectrum of Mercury

    Homework Statement For our investigation, we used a diffraction grating spectrometer to observe the emission spectrum of mercury. We conducted the experiment in a pitch black room to avoid any unwanted light pollution, etc. Whilst conducting the experiment we observed a number of 'faint' lines...
  28. Eagertolearnphysics

    Diffraction grating problem

    Homework Statement Yellow sodium light, which consists of two wavelengths, λ_1 =589.0 nm and λ_2 = 589.89 nm, falls on a 7500 lines/cm diffraction grating. Determine (a) the maximum order m that will be present for sodium light, (b) the width of grating necessary to resolve the sodium lines...
  29. clamatoman

    Diffraction Grating - all visible light?

    Homework Statement Find the smallest grating spacing that let's you see the entire visible spectrum. 400nm to 700nm comprises the visible light spectrum. no other information is given. Homework Equations nλ=d sin θ The Attempt at a Solution I am not sure how to start as all i have been given...
  30. KennedYeti

    Diffraction Grating and Visible Light

    Homework Statement "You're using a diffraction grating o view the 400 to 700 nm visible spectrum. Suppose you can see the spectrum through the third order. a) Show that the first and second order spectra never overlap regardless of grating spacing. b) show that the second and third order...
  31. S

    Diffraction grating problem involving Snell's Law

    Homework Statement A 600 line/mm diffraction grating is in an empty aquarium tank. The index of refraction of the glass walls is [n][/glass] = 1.50. A helium-neon laser (lambda=633 nm) is outside the aquarium. The laser beam passes through the glass wall and illuminates the diffraction grating...
  32. H

    An experiment using a diffraction grating with

    Homework Statement An experiment using a diffraction grating with a monochromatic light source is performed to create an interference pattern on a screen. Consider the following changes: I. Increase the line density of the grating. II. Decrease the frequency of the source. III. Increase...
  33. JulienB

    Optics: dispersive power of diffraction grating

    Homework Statement Hi everybody! Here is the problem I am trying to solve: a) A source illuminates a grating in a spectroscopical element so that the principal maxima appear as thin bright bands (therefore the name "spectral lines"). Show that the angular width ##\Delta \theta## of such a...
  34. P

    Diffraction Grating Question, Dispersion and Resolving

    Homework Statement One diffraction grating has 9600 lines uniformly spaced over a width of 3cm, it is illuminated by light from a mercury vapour discharge. The other has 5000 lines/cm and is a 3.5cm grating, this one is used in the second order to resolve spectral lines close to 587.8002 nm...
  35. ReidMerrill

    Diffraction Grating wavelength

    Homework Statement A) Find the diffraction order from the grating that has an angle of incidence of 40 degrees and a diffraction angle of 20 degrees. The wavelength of incident light is 500nm and the spacing between the grooves on the grating are 5 micrometers B) If I want to selectively emit...
  36. H

    Two Diffraction Gratings - Rotation

    Can someone explain how the laser pointer is generating the rectangular patterns shown in this youtube video? I assume that there are just two diffraction gratings that are rotated relative to each other, but could someone explain mathematically how to predict what pattern is formed for...
  37. tenzinlhazey

    Solving Diffraction Grating Angle: Can it be 90°?

    You know when you have diffraction gratings, you have to measure the angle between center and first order/maxima right? My question is: can the angle be 90°? Or is it always less than that? d sin θ = nλ Thank you!
  38. EmilyBergendahl

    Calculating the Number of Lines on a Diffraction Grating

    Homework Statement A diffraction grating gives a second-order maximum at as angle of 31° for violet light (λ = 4.0 × 10^2 nm). If the diffraction grating is 1.0 cm in width, how many lines are on this diffraction grating? Homework Equations d = (m)(λ)/sinθm The Attempt at a Solution d =...
  39. EmilyBergendahl

    The Diffraction Grating (Grade 12 Physics)

    Homework Statement Do the maxima created by a diffraction grating all have the same intensity? Explain. Homework Equations mλ = wsinθ (?) The Attempt at a Solution According to the back of my textbook (Nelson Physics 12), the answer is no. I believe the answer may have to do with the fact...
  40. A

    Electron Velocity Diffraction Grating Problem

    Homework Statement Suppose that visible light incident on a diffraction grating with slit distance (space) of $0.01*10^{-3}$ has the first max at the angle of $3.6^{o}$ from the central peak. Suppose electrons can be diffracted with this same grating, which velocity of the electron would create...
  41. Tazerfish

    Strange Optical Phenomenon (diffraction or something else?)

    First of all i will post a picture of it ... you can find it ... somewhere sorry this is my first post :I I photographed our television with the flash on in order to recreate a strange patter i saw when looking at the suns reflection in the screen.(with my eyes it's not just the camera) You can...
  42. kamhogo

    Single-sit vs. Double-slit vs. Diffraction grating

    Homework Statement Briefly state one characteristic of single-slit /double-slit/diffraction grating interference pattern that allow you to clearly distinguish one from the others. Homework Equations NoneThe Attempt at a Solution Single-slit: Taller, broader central maximum.Double-slit: More...
  43. velkyr

    Rayleigh criterion (two wavelengths) + diffraction grating

    Homework Statement "A source emits light with two monochromatic components of wave-lengths λ1 = 510.50 nm and λ2 = 510.90 nm. Using the Rayleigh criterion, find the minimum number of slits of a grating that must be illuminated by a beam from the source in order to resolve these components."...
  44. M

    Focal length of diffraction grating for recip. dispersion

    Homework Statement What would the focal length be of a diffraction grating if the set up is a laser placed 1 m from the 0 order diffraction? Would it be the distance from the grating to the laser or the distance from the grating to the image? Homework Equations 1/f = 1/o + 1/i Rd = [Df]-1...
  45. C

    Diffraction Grating Relationship Question

    Homework Statement A diffracting grating casts a pattern on a screen located a distance L from the grating. The central bright fringe falls directly in the center of the screen. For the highest-order bright fringe that hits the screen, m=x, and this fringe hits exactly on the screen edge. This...
  46. B

    Diffraction Grating Homework: Find the Distance of Bright Fringes

    Homework Statement You shine a red (λ = 650 nm) laser beam and a green (λ = 532 nm) laser beam at a diffraction grating that has 400 slits/mm to create an interference pattern on a wall 2.30 m from the grating. If the two lasers are directly on top of each other, how far apart are the two m = 1...
  47. T

    Diffraction grating, distances between maxima

    Homework Statement A grating has a line density of 1010 cm−1, and a screen perpendicular to the ray that makes the central peak of the diffraction pattern is 2.5 m from the grating. If light of two wavelengths, 590 nm and 680 nm, passes through the grating, what is the separation on the (flat)...
  48. toforfiltum

    Diffraction grating that gives max intensity

    Homework Statement Homework Equations dsinθ=nλ IαA2 The Attempt at a Solution I chose D because I thought that D gives the max intensity since the amplitudes superimpose over a smaller area. But the answer is C. I can't see why.
  49. Shahab Mirza

    Diffraction Grating Problem ?

    Hi, 1. Homework Statement Q : A diffraction grating with 10000 lines per CM is illuminated by yellow light of wavelength 589 nm, At what angles is the 2nd order bright fringes seen ?Homework Equations From my textbook , I got this equation , d sin theta = m (λ) The Attempt at a Solution Ok so...
  50. S

    Light problem -- diffraction grating distance between adjacent bright fringes

    Homework Statement Light from a laser with a wavelength of 760 nm is directed at a diffraction grating of 1500 lines/cm. If the diffraction grating is located 1.5 m from the screen, calculate the distance between adjacent bright fringes. Homework Equations Δx = Lλ / d 760 nm = 7.60 x 10^-7 m...
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