What is Wavelength: Definition and 1000 Discussions

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. T

    Blackbody Radiation - Peak wavelength

    Homework Statement The Planck blackbody spectrum is given by u(ω,t)=\frac{ħω^3}{π^2c^3(e^{βħω}-1)} Show that the peak of the Planck spectrum for a blackbody at a temperature T occurs at the wavelength λ_{max}T=0.29 where T is in Kelvin and λmax is in cm. Homework Equations...
  2. T

    Change in energy as light passes through air/water

    Okay, best to provide some background here. I am trying to understand the light coming from the LED's over my aquarium. I have blue moon lights I think at about 540nm and 450nm. Oddly enough, when they are on, there is a green tinge to the light. I had assumed that this was because the light...
  3. K

    Sound frequency from distance b/w first minimum and maximum

    Homework Statement Two speakers are arranged as shown. For this problem, assume that point O is 12 m along the center line and the speakers are separated by a distance of 1.5 m. As the listener moves toward point P from point O, a series of alternating minima and maxima is encountered. The...
  4. avito009

    I Blu-Ray Disc: Shorter Wavelength, Bigger Storage?

    blu ray disc has a shorter wavelength than a red laser (650nm), but how does having shorter wavelength effect storage space? answer in laypersons terms.
  5. Davephaelon

    I Can Cooper Pairs in Superconductors Interact Over Long Distances?

    Do the de Broglie wavelengths of Cooper pairs, in a superconductor, overlap one another, over distances of say hundreds, or thousands of lattice spacings?
  6. E

    I LIGO light changes frequency not wavelength

    Gravitational wave stretches and shrinks space. Why Laser light in Ligo arms changes frequency, and not wavelength.Is it some clear explanation? If even frequency would not be changed than spacetime is not changed, I suppose. What cannot be measured, cannot exist.
  7. A

    A The de Broglie wavelength: What happens in the case of a frame change?

    I have a problem to understand the de Broglie wavelength. We know that also particles undergo scattering and interference at a double slit. The interference pattern is calculated by the use of the de Broglie wavelength which is defined as lambda = h / p ; p is the momentum of the particle. This...
  8. edguy99

    I Is SLAC producing light "light with a wavelength of 32nm"?

    I am looking for clarification of the wording used in a recent article about X-ray lasers. https://www6.slac.stanford.edu/news/2016-06-06-echo-technique-developed-slac-could-make-x-ray-lasers-more-stable.aspx ... researchers have been trying to generate higher and higher harmonics, with the...
  9. JulienB

    Photoelectric effect at wavelength 492nm for mercury

    Homework Statement Hi everybody! I just did the photoelectric experiment this week, and I have a report to write about it. We used a mercury vapour lamp, a set of metal interference filters and a grey filter in order to find the intersection point (and therefore ##U_{g,max}## between the...
  10. J

    Relationship between frequency, wavelength, and speed

    Hi there, I am in need of another's thoughts on this topic. I at first thought frequency is something that doesn't change and is inherent to the source, so then increasing the wavelength shouldn't lead to an increase in frequency, but an increase in speed. I realized later that this only...
  11. Nile Anderson

    Determining the Wavelength of Sound using Resonance Tube

    Homework Statement [/B]Homework Equations I honestly do not know any relevant equations for this relationship. Well except f=v/2l. The Attempt at a Solution The only thing I could assume that it was was some sort of error , but I cannot find much material on the topic , so I was hoping to get...
  12. A

    I Discovery of how to measure wavelength absorption lines

    who was the first person to discover how to measure the wavelength of absorption lines in the solar or stellar spectra and what method was used?
  13. alv

    I 1 pm de Broglie wavelength? What's pm?

    I'm reading about delayed-choice experiments http://arxiv.org/pdf/1407.2930.pdf and in this sentence "In modern interferometric experiments, the wave nature of molecules of approximately 7000 atomic mass units and 1 pm de Broglie wavelength has been demonstrated" I can't figure out or find out...
  14. Z

    Show interparticle spacing is much greater than wavelength

    I have a past paper question from statistical physics: By assuming that ##\hbar^2 k^2=p^2##, I arrived at the result: The interparticle spacing, ##a^3 =\frac{V}{N}## is $$ a^3 >> e^{-\frac{p^2}{2mk_B T}} \lambda_{deB}^3$$ Is my assumption correct? and does the result complete the purpose of...
  15. N

    Why frequency is more fundamental than wavelength?

    Please anyone explain that why frequency is more fundamental than wavelength inspire wavelength and frequency depend upon each other again frequency and wave number are also depends upon each other Then why we take the frequency as independent of wave number
  16. C

    Calculating frequency and wavelength in solution

    Homework Statement A laser beam is incident at an angle of 30.0° from the vertical onto a solution of corn syrup in water. The beam is refracted to 22.84° from the vertical. (a) What is the index of refraction of the corn syrup solution? I already got the answer of 1.29. (b) Assume that the...
  17. H

    Finding Maximum Number of Interference Maxima?

    Homework Statement Light of wavelength λ = 535 nm shines through two narrow slits which are 670 μm apart. What is the maximum number of interference maxima which could conceivably be observed (assuming that diffraction minima do not extinguish them and the screen is arbitrarily large)?Your...
  18. vetgirl1990

    Calculating Wavelength from Radiative Power and Orbital Geometry

    Homework Statement The first unmanned probe will reach the stellar system of the Alfa Centauri (estimated radius 5x104 km) in year 2145. The probe will enter stationary orbit of radius R 300 x106km around the star. In order to power itself the probe will convert the radiative energy received by...
  19. bachfromthedead

    Finding the deBroglie wavelength: conceptual issue

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  20. M

    I Hydrogen Atom Photon Emission Wavelength Formula

    I am trying to calculate the Lyman-alpha wavelengths of photons emitted from different hydrogen-like atoms such as deuterium and positive helium ion 4He+, using the relation 1/λ = R*|1/ni^2 - 1/nf^2|, where R is the Rydberg constant and ni and nf are integer numbers corresponding to the initial...
  21. astrof

    I De Broglie wavelength - relativistic correction

    According to the wiki page: http://en.wikipedia.org/wiki/Matter_wave the generalised form for the de Broglie wave is simply: \lambda = h/p I suppose this not correct, because there is no trasform which can change only one side of the equation. In this case we have two variables: 1. a momentum...
  22. O

    A De Broglie Wavelength - Compound Particles, Particle Systems

    Can someone describe the physical processes which distinguish between separate and single particles when dealing with a collection of particles in the context of the De Broglie wavelength? The De Broglie wavelength is inversely proportional to the momentum of a "particle". Assume "separate"...
  23. BsNLucky

    Equation for photocurrent dep. wavelength, diffusion length,

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  24. DavidReishi

    B Wavelengths corresponding to fractions of nanometers?

    In terms of the electromagnetic spectrum, are there wavelengths of light corresponding to fractions of nanometers, for example, 0.5 nm, with their own photon energies? Or are whole nanometers "nature's smallests units" when it comes to the various existing wavelengths of light?
  25. G

    Refraction, wavelength and frequency

    I've learned that when wavelength increase the frequency decreases. But in Refraction, there is a mention about frequency remains same but the wavelength and speed changes. Why does the frequency doesn't change? I thought when when wavelength is short the peaks are closer to each other so...
  26. TheExibo

    Wavelength from amplitude information?

    Homework Statement A string vibrates at its third-harmonic frequency. The displacement at a point 59.0cm from one end is the first time the displacement is half the maximum amplitude. How long is the string? Homework Equations wavelength=(2(rope length))/nodes y=Asin(kx) k=2pi/wavelength...
  27. Ryaners

    (Statistics) Blackbody spectrum in terms of wavelength?

    This is a question about transforming a probability distribution, using the blackbody spectrum as an example. Homework Statement An opaque, non-reflective body in thermal equilibrium emits blackbody radiation. The spectrum of this radiation is governed by B(f) = af3 / (ebf−1) , where a and b...
  28. Oaxaca

    B DeBroglie Wavelength with Relativistic Electron

    I am trying to find the DeBroglie wavelength of an electron moving at .8c. I have never learned special relativity but I believe the momentum is affected (mass change). I used the formula p= (mv)/(1-v^2/c^2) and got a momentum of p = 2.733 E-22 and a wavelength of lamda = 2.4149 E-12. Did I...
  29. T

    Find Wavelength of 8cm Closed Pipe: 7th Harmonic

    Homework Statement What is the wavelength of an 8cm closed pipe when it is sounding the 7th harmonic? Homework Equations L=λn/4 The Attempt at a Solution L=(.08m*7)/(4) L=0.14m Am I correct?
  30. LLT71

    Light: same frequency=different wavelength?

    can someone explain why light waves have the same frequency when they pass through different mediums, and at a same time they have different wavelenghts? if frequency=speed of light (which is constant I assume) /wavelength, how could it be? does the speed of light somehow changes when light...
  31. Stella.Physics

    Color of Light: Frequency vs Wavelength.

    So today I was thinking that color is connected with a given wavelength (for example red light in air is about 600nm) but after some research online I found out that color depends on the frequency and when light travels through various optical media (like air, glass etc) speed and wavelength...
  32. A

    A Plank Radiation Spectrum Liquids Wavelength VS Temp

    Hello, Are there any Plank Radiation Spectrums for liquids? What I really want to know is, for a given liquid, what wavelength of light is emitted for a given temperature. For example, if I journey to the center of the Earth, the molten lava is about a thousand degrees, hot enough to emit red...
  33. T

    How to understand wavelength in a simple way

    Guys, i"m only 13 and i somehow got curious in astronomy. I want to know how wavelength works in a simple way. Please help me guys :P
  34. W

    Compton Scattering; Relation between scattering angles

    Homework Statement Show that the scatter angles of the photon (θ) and electron (Φ) in the Compton effect are related by the relation: ##cot (θ/2 )=(1+\frac{hf}{mοC^2}) tan(Φ) ## Where f is the frequency of incident photon 2. The attempt at a solution I wrote down the equations of conservation...
  35. LLT71

    B Why don't we use arc length formula to calculate wavelength?

    can you please explain me why don't we use arc length formula to calculate wavelength? seems a bit confusing...
  36. Physicist50

    Solar Cells & Refractive Index

    Hi there, I have recently been researching in depth solar cells/panels, the parameters of their efficiency and the photoelectric effect in general, specifically how different wavelengths of light affect it. My research has yielded a few facts; that the efficiency of standard silicon solar cells...
  37. yango_17

    Electron in a box - wavelength of photon

    Homework Statement a) An electron is trapped in a one-dimensional box that is 526 nm wide. Initially, it is in the n=2 energy level, but after a photon is absorbed the electron is in the n=7 energy level. What is the wavelength of absorbed photon? b) Eventually, the electron ends up in the...
  38. Anand Sivaram

    Perceived Color of objects: in White light from a TV

    Background: Normal white Sun light has a continuous spectrum in the whole of visible range. But, white light (rather what we perceive as white) coming out of a Monitor/TV is have only RGB in it and it looks white because of the Tricolor vision which excites all three types of cells in the eye...
  39. SpicyWassabi101

    Relationship between temperature and wavelength?

    Homework Statement A tuning fork with a frequency of 420 Hz emits sound with a wavelength of 0.82 m in air. If the temperature of the air increases, what will happen to the wavelength and why? Homework Equations The Attempt at a Solution I know temperature affects speed but I am not so sure...
  40. Mr Davis 97

    Changing wavelength with changing tension

    Homework Statement A rope is hanging vertically straight down. The top end is being vibrated back and forth, and a standing wave with many loops develops on the rope, analogous (but not identical) to a standing wave on a horizontal rope. The rope has mass. The separation between successive...
  41. pioneerboy

    EM length of gravitational waves

    Maybe a stupid question and maybe sensless to ask, but as I don't know, I ask anyway: what is the length of the newly found gravitational waves in terms of traditional EM wavelengths?
  42. S

    MATLAB Center Wavelength of Fiber Bragg Grating Filter

    I would like to locate the center wavelength of a FBG notch filter in MATLAB, but I'm having trouble getting an answer within 0.01nm of the correct wavelength. So far I've tried using a quadratic fit with MATLAB, but that is too dependent on the amount of data points to the left and right of...
  43. Isaac0427

    Solving for Wavelength: What Did I Do Wrong?

    De Broglie's postulate states that λ=h/p and ƒ=E/h. If you plug in E=pc, then you get λ=c/ƒ. Using the equation for wavelength λ=v/ƒ, I found that v=c, but this can't be true, because the matter waves would be traveling a c. What did I do wrong? Thanks!
  44. K

    Understanding Minimum Path Difference for Waves Below the Centerline

    Homework Statement Homework EquationsThe Attempt at a Solution (Sorry my poor English). I just don't understand why should the minimum path difference be 0.75 wavelengths for angles below the centerline instead 0.25 wavelenghts as it is for angles above the centerline.
  45. Mr Davis 97

    Does the Doppler Effect Affect Wave Velocity in Moving Observers?

    Imagine that there is a stationary source that is propagating waves (such as sound waves). Let's say that the wave speed in the medium is 343 m/s. If I am an observer, and I begin to move towards the waves, will the wave speed increase due to the idea of relative velocities, or will only the...
  46. A

    Minimum wavelength of electrons ejected from metal

    Homework Statement This problem has two parts. A laser produces photons having an energy, E = 3.5eV. a) What is the wavelength of photons produced, assuming that the index of refraction is 1.6? ->221nm b) If this laser beam is focused on the clean surface of a metal having a work function of...
  47. L

    What is the wavelength of an electron of 5eV energy?

    Homework Statement Calculate the wavelength of an electron which has 5eV of energy.Homework Equations de Broglie's equation: lambda=h/p , kinetic energy equation: K=0.5mv^2 The Attempt at a Solution My attempt: I figured out that using de Broglie's wavelength equation was necessary for this...
  48. durant35

    De Broglie wavelength and velocity

    I was wondering about the equation for the de Broglie wavelength which indicates that the wavelength of any object is shorter when the object is moving faster. Why does this occur? And how we connect this with special relativity where the velocity depends on the frame of reference.
  49. Alan Boxx

    Does the wavelength for photodissociation of hydrogen vary?

    Photodissociation of hydrogen at ground state requires a 273nm wavelength for a photon particle to dissociate H2--> H- + H+. But what about hydrogen at higher states of energy? Is the 273nm a constant? If not, what is the formula for min. wavelength for higher energy states...
  50. T

    Why does 2slit interference depend on wavelength?

    How do 2 waves in a double slit get cut? I know that light spreads in all directions so, when a double slit is infront of a light source, then it only allows light that goes through the slit past the wall. Why do interference patterns depend on the wavelength? Isnt the wave length perpendicular...
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