Wavelengths Definition and 231 Threads

In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, troughs, or zero crossings, and is a characteristic of both traveling waves and standing waves, as well as other spatial wave patterns. The inverse of the wavelength is called the spatial frequency. Wavelength is commonly designated by the Greek letter lambda (λ).
The term wavelength is also sometimes applied to modulated waves, and to the sinusoidal envelopes of modulated waves or waves formed by interference of several sinusoids.Assuming a sinusoidal wave moving at a fixed wave speed, wavelength is inversely proportional to frequency of the wave: waves with higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths.Wavelength depends on the medium (for example, vacuum, air, or water) that a wave travels through. Examples of waves are sound waves, light, water waves and periodic electrical signals in a conductor. A sound wave is a variation in air pressure, while in light and other electromagnetic radiation the strength of the electric and the magnetic field vary. Water waves are variations in the height of a body of water. In a crystal lattice vibration, atomic positions vary.
The range of wavelengths or frequencies for wave phenomena is called a spectrum. The name originated with the visible light spectrum but now can be applied to the entire electromagnetic spectrum as well as to a sound spectrum or vibration spectrum.

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  1. L

    Speed of light of different wavelengths in medium

    Hello, As we all know, speed of light of different wavelengths (let's say red and blue) in vacuum is same. However, in medium (like glass) it's different and depends on a wavelength and a refractive index. Let's say we send a short pulse of white light incident into a piece of glass (of length...
  2. I

    Which wavelengths cause the photolysis of water to happen?

    I was wondering which specific wavelengths of light cause the photolysis of water to happen.
  3. JG1009

    Optical Pumping & Laser Wavelengths

    During optical pumping in a laser, is the wavelength of light that corresponds to the transition from the metastable state that yields the laser light removed? Otherwise, wouldn't a population inversion not be possible as these photons from the optical pumping would cause stimulated emission...
  4. G

    Dichroic mirrors that reflect two wavelengths

    In fluorescence microscopy, dichroic mirrors reflect light under a critical wavelength (used to excite the sample) and transmit light over a critical wavelength (emission light from the sample). Are there mirrors that reflect two different wavelengths of light and transmit the rest? Essentially...
  5. neilparker62

    Lyman Series Wavelengths - measurement standard?

    Am just wondering what the currently accepted measurement standard is for the Lyman series spectral lines. At NIST I find the following set of measured wavelengths (nano meters): 91.9342 92.0947 92.3148 92.6249 93.0751 93.7814 94.9742 97.2517 102.5728 121.56701 At...
  6. R

    Calculating the Wavelength Ratio of Kα X-Ray Lines for Copper and Molybdenum

    Homework Statement If λCu is the wavelength of Kα X-ray line of copper (atomic number 29) and λMo is the wavelength of the KαX-Ray line of molybdenum (atomic number 42), then the ratio λCu/λMo is close to 1.99 2.14 0.50 0.48 Homework Equations De broglie relation λ = h/p The Attempt at a...
  7. S

    Help with periods and oscilation *and* wavelengths

    Homework Statement Water waves in a shallow dish are 6.0 cm long. At one point the water oscillates up and down at a rate of 4.8 oscillations per second. a. What is the speed of the water waves? b. What is the period of the water waves? Homework Equations frequency = 1/period Speed =...
  8. julianwitkowski

    How to Calculate Wavelength in a Two-Dimensional Wave Interference Pattern

    Homework Statement Using the two-dimensional wave interference pattern shown and the two equations involving path difference, complete the following. i) measure the wavelength of the waves ii) measure the distance between sources iii) measure the path distance from each of the sources to the...
  9. Spock

    What are the Wavelengths and Amplitude of these particles?

    What would the Wavelength of these particles be? Also if you could, what would the amplitude be, I'm guessing 0.
  10. N

    Probability amplitudes & light / particle wavelengths

    So this is basic question but the more I read the more I am confusing myself! I was assuming that the wavelength of a photon was the same wavelength as the associated probability amplitude (although a complex number). So to make constructive interference it means one path takes say ten...
  11. S

    Positronium emitted wavelengths

    Hey everyone so I'm having some trouble figuring out how to approach this question. I don't need a step by step solution just an idea of how I should approach the question and maybe some specifics on how to apply needed concepts such as reduced mass. Thank you. "Assuming positronium were a...
  12. U

    Refraction-Speed difference at different wavelengths

    Hi all, I've read that when light undergoes refraction into a medium with higher refractive index it changes speed and this is explained by the electrons of the medium absorbing the photon energy, they hold onto it then eventually re-emit the light if the frequency of light doesn't match the...
  13. K

    Planck's law for longer wavelengths

    I was just working on a problem that asked me to show that Plank's Law for black body radiation is approximately equal to Rayleigh-Jeans Law, which expresses the energy density of black body radiation as a function of wavelength. I was to show that this relation is only true at high wavelengths...
  14. Esfand Yar Ali

    About compton's effect of shift in wavelengths

    I want to know that ,I have read in many books regarding compton's effect that a photon collides with an electron and this collision is a head-on collision,but if this is a head-on collision then why both these particles are deflected by making a respective angle,don't they should move forward...
  15. D

    Interference of microwave transmitters of different wavelengths

    This question is about the interference pattern observed when the waves from two microwave transmitters interfere. The first parts of the question involve the wavelengths of microwaves being the same for each transmitter. For the last part the question proposes that the wavelength of one of...
  16. A

    Exploring Sunlight in the Atmosphere: IR Wavelengths

    Can anyone speak on the spectrum of sunlight reaching the upper atmosphere and the surface ? Specifically I interested in finding out if there are any IR wavelengths disproportionally represented when compared to the original source. Please limit responses to constructive ones.
  17. U

    WaveLengths of Light Waves and their respective photons

    Suppose you have a source of light that emits light with a wavelength of 2 meters, and you set the device to be turned on and switched off alternately. You also set it so that each interval the device is turned on is only long enough for 1 meter to be emitted (1/2 a wavelength). Do you ever...
  18. DanielMB

    Is our Vision System sensitive to Wavelengths or Frequencies?

    Our Vision System should be sensitive to one specific term, they do not mean the same, one is related with geometry factors (wavelength) while the other is related with beating stimuli (pulse) The frequency of light (f) is constant from media to media, the same as it is in vacuum, wavelength...
  19. Y

    Converging Lasers of Different Wavelengths

    I hope this is the right place to ask this. It is an experiment question. I have a 785 nm laser and a 1550 nm laser and I need to converge them down to a point. Now I could just manually align the lasers on the same XY-plane and have them hit that spot, but for reasons I don't want to...
  20. G

    Wavelengths of standing waves on a string

    Homework Statement Consider a string of length L held fixed at both ends. The string can be shaken up and down and, at certain frequencies, the result will be a standing wave pattern on the string. Find the five longest wavelengths (call them λ1, λ2, λ3, λ4, and λ5) of the standing wave...
  21. C

    Fringes from Different Interfering Wavelengths

    Homework Statement The questions is... Coherent light with wavelength 597nm passes through two very narrow slits, and the interference pattern is observed on a screen a distance of 3.00 m from the slits. The first-order bright fringe is a distance of 4.84 mm from the center of the central...
  22. R

    Can you combine wavelengths to ionize atoms

    If I have an atom with energy levels of -4 ev, -2 ev -1 ev and 0 ev and I radiate it with photons which cover a continuous range from 0 to 2 ev is it not possible for a 2 ev photon to move the electron from -4 to -2 and then a 1 ev photon to move it from -2 to -1 and then a 2 ev photon to free...
  23. J

    Why don't we see scattered wavelengths of light?

    So Rayleigh scattering says that higher wavelengths of light are scattered more than lower ones - but why don't we ever see the scattered wavelengths anywhere? Is it just because when they're scattered they have lower intensities and are outshined by blue?
  24. M

    Highest order of spectrum given two wavelengths

    Homework Statement I've attached the problem Homework Equations d*sinθ=mλ The Attempt at a Solution I've tried a couple of methods. I considered solving for m when θ=90 degrees => sinθ=1 because 90 degrees is the highest possible angle and will (in my mind at least) yield the highest order...
  25. T

    Seperation for third order maxima for two wavelengths - help please

    Homework Statement A grating has 1070 lines per centimetre, and a flat screen is perpendicular to the ray that makes the central peak of the diffraction pattern. The screen is 3.20 m from the grating. If light of two wavelengths, 630 nm and 705 nm, passes through the grating, what is the...
  26. P

    Emission spectrum wavelengths.

    Something that bugged me when doing this lab. Standard little glass vials of gas, toss it in a 5kV potential make pretty color, look through diffraction grating see the individual wavelengths that are the finger prints of the element. My question however are all wavelengths equally...
  27. L

    Modern Physics Lab: Hydrogen Wavelengths & Energy Levels

    This question is based on a modern physics lab I'm working on, and it's conceptually killing me. 1. Homework Statement For hydrogen, compare your measured wavelengths to the predicted wavelengths for hydrogen. Assuming the lower level is the same for all the lines you observed in the...
  28. R

    How can I find the length of a day on Jupiter from wavelengths?

    The question is: the wavelength of a spectral line on the left edge of Jupiter's equator is 499.98 nm, and the right edge is 500.02 for the same spectral line, what is the length of jupiter's day (in hours)? I know that its 10 hours but I need to show my work. I tried using many different...
  29. I

    Minimizing Reflected Light Wavelengths

    Hey there, I'm new here mainly because I realized how deficient my ability to think in Physics/Math based scenarios really is, plus if I'm going to stay in Premed I need to pass a Phys 101 course in 1st year. So, my question is this.. The windows in an office tower are coated with a film...
  30. K

    Relating absorbance wavelengths and refractive index

    Dear All, thank you for your attention. I am a Biologist and I was wondering if it is possible to translate absorbance λ values into a refractive index value? I found out about the sellmeier equation however it appears to require coefficients that have to be experimentally determined...
  31. K

    Does gravity affect to wavelengths?

    My question is... Does the wavelength of light (in vacuum space, of course) suffer changes as it approaches to a gravity field, or simply stays the same?
  32. V

    Color addition involving wavelengths

    recently i have been thinking about how colors add when you have 2 different light sources of color and put the streams together, such as taking red and green beams and crossing them to make yellow. i was looking at wavelengths to determine if there was a mathematical way to say what color would...
  33. Q

    Why are only certain wavelengths reflected when light strikes a wall?

    This is my first forum post so I apologize in advance if I do not provide enough detail, speak clearly enough, or violate some forum etiquette. I have a few questions here all relating to the same thing so hopefully this isn't worded poorly or too much. When light strikes a surface, the...
  34. N

    Understanding de Broglie Wavelengths

    I understand the derivation and calculation of de Broglie wavelengths. What I don't understand is what exactly they are. What does the wavelength of a particle mean? Does it mean the wavelength of its probability wave, or some other kind of wave? The idea of wave-particle duality for EMR...
  35. D

    Question about de broglie wavelengths

    Homework Statement Assume that the total energy E of an electron greatly exceeds its rest energy E0. If a photon has a wavelength equal to the de Broglie wavelength of the electron, what is the photon’s energy? Repeat the prob- lem assuming E = 2E0 for the electron. I need help with the first...
  36. R

    Finding the Distance between fringes given different wavelengths

    Homework Statement See attached image Homework Equations single wavelength mλ=dsin(θ) diffraction grating: d*(sinθi+sinθm)=mλ y/L = sinθ The Attempt at a Solution red = 656 nm blue = 486 nm L = 1.7 m I really do not know what to do. I tried 656-486 = 170 nm so...
  37. S

    Doppler Effect: Moving Objects & Wavelengths

    Hello, what is referred to that every moving body has an associate wavelength ? thank you
  38. T

    Wavelengths of sunlight, blackbody radiators, Planck's law, CCT

    A blackbody radiator emits radiation across the entire radiation spectrum. The "temperature" of the blackbody radiator (measured in kelvin) can be directly calculated from the peak wavelength of its radiation using http://en.wikipedia.org/wiki/Wien's_displacement_law"]Wien's[/PLAIN]...
  39. K

    Calculating Energy Levels and Wavelengths in the Hydrogen Atom

    Homework Statement In the hydrogen atom, the electron jumps from the n = 1 level to the n = 4 level. a. During this transition from n = 1 to n = 4, is a photon emitted or absorbed? b. What is the change in energy of the electron? c. State the transition in words. d. What is the wavelength...
  40. P

    Determining Bond Length with Wavelengths

    Homework Statement Calculate the bond length for the NaCl molecule given that three successive wavelengths for rotational transitions are 23.1 mm, 11.6, mm and 7.71 mm. Homework Equations I = h*wavelength/4pi*speed of light. The Attempt at a Solution I don't understand how to...
  41. C

    Calculating the transmission of a 1mm thick silicon wafer at various wavelengths

    I am intending to perform extended absorption fine structure (EXAFS) experiments on a thin film in order to investigate the near order around Europium ions. The thin film is going to be deposited on a silicon substrate, and the question is in reality related to how thick the substrate should be...
  42. M

    How to Calculate Kα and Kβ Wavelengths for Helium and Lithium?

    Homework Statement Calculate the Kα and Kβ wavelengths for He and Li Ive seen https://www.physicsforums.com/showthread.php?t=118050 and the two websites that were given for tables, but I need to show calculations. Homework Equations K alpha Energy=10.2eV*(Z-1)2? E=hc/λ The...
  43. X

    Wavelengths of Particle passing Potential Barriers

    Homework Statement Compare the wavelengths of a particle when it passes a barrier of height (a) +V0 and (b) -V0 where E > |V0|. Calculate the momentum and kinetic energy for both cases. Homework Equations (see below) The Attempt at a Solution I know the wavelength changes in the...
  44. C

    Bohr model electron wavelengths

    Hi I know that in the Bohr model, electrons move between energy levels, but you don't hear much about the electron's wavelength at each particular level. If we assume the orbits contain an integer multiple of wavelengths, you get the usual $$2\pi r=n\lambda,$$ so, based on the expression for...
  45. M

    Temperature of planets from their Luminosities at specific wavelengths.

    Hi! I have worked on this for a while and cannot seem to get a reasonable answer. I have been given the Luminosities of planets at different wavelengths and I need to determine the Temperature. I re-arranged Planck's equation to find T but I keep getting really low temperatures Planet A...
  46. N

    Are there mirrors/panels capable of reflecting designated color wavelengths?

    I was thinking today about whether or not mirroring could be altered to reflect only certain wavelengths of the spectrum? I couldn't think of specified way to do such a thing, thought maybe some more adapted minds could lend some advice. Thanks for any help on the topic.
  47. S

    Wavelengths in fused silica and in silicon for photons

    Homework Statement Compute the wavelengths in fused silica and in silicon for photons whose free-space wavelengths are 800 nm, 1300 nm, and 1550 nm. Homework Equations This is the problem, I'm not sure what equation to use and the textbook does not seem to say, well what little I have of...
  48. O

    Why Does Andromeda's Wavelength Calculation Differ from Hubble's Law?

    I have calculated the wavelength of a line that would be observed in a spectrum from Andromeda where speed and λ0 were known, using the formula z =∆λ/λ0 and z=v/c. I obtained a value smaller than λ0 because Andromeda display a blue shift. After I calculated the same wavelength pretending that...
  49. H

    Sine Function with Alternating Peaks and Wavelengths

    Hi All, I'm trying to find a sine function that models the cyclic and seasonal nature of retail sales across the years. I've tried several combinations including some basic attempts at complex plots of sin(x), but am now starting to wonder if there is even a simple solution to the problem...
  50. W

    Analytical Chemistry UF: Comparing Wavelengths & Frequencies

    Question 20 from our final I just took (Analytical Chemistry UF). "You may recall that the wavelength of the sodium D1 line in vacuum is 589.7558nm. In air it becomes 589.5924nm. What is the difference in frequency for these two wavelengths." I said 0. All the other people did the...
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