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. M

    De Broglie Wavelength Calculation given electron velocity

    Homework Statement an electron is moving at 2.5 x 105m/s. Find the electron's De Broglie Wavelength. Homework Equations De Broglie relates wavelength of electron waves to momentum of the electron by lambda = h/p where h is Planck's constant. The Attempt at a Solution given the...
  2. D

    Finding wavelength with just frequency?

    One radio station in the middle of the FM band has a frequency of 95.0 MHz. What is its wavelength? lambda=v/f I assume that the velocity of the wave is 343 m/s. I convert 95MHz to Hz, which is 95,000,000 Hz. lambda=(343 m/s) / 95,000,000 Hz. I come up with 3.51e-6. Webassign...
  3. F

    Does a single photon have a wavelength?

    If a single photon has a wavelength, would it violate Heisenberg Uncertainty principle? Since photon is a particle, that means it can be represented by a wave packet. But wave packet can not have definite wavelength, only pure wave can have wavelength
  4. M

    The Brogile wavelength of an Alpha particle

    Homework Statement An alpha particle of energy 5.78 MeV is emitted from a particular nucleus. Calculate the de Broglie wavelength of the alpha particle. How does it compare with the nuclear diameter, which is known to be approximately 2x10−14 m. Homework Equations E=h/p and E=hf...
  5. L

    Wavelength of 4.00 p to 4.00 s Transition in Sodium

    Homework Statement Consider a 4.00 p to 4.00 s transition in sodium. What is its wavelength Homework Equations The Attempt at a Solution
  6. W

    Determining the Best Wavelength for Darwin's Space Mission

    here's the question: 'Darwin is a proposed space mission to detect thermal radiation from Earth-like planets. Estimate the best wavelength for carrying out observations with Darwin.' i'm guessing we need to use wien's law(from an earlier part of the question), and so we need the absolute...
  7. M

    Interference pattern, wavelength

    Homework Statement Suppose the interference pattern shown in the figure is produced by monochromatic light passing through two slits, with a separation of 127 µm, and onto a screen 1.14 m away. What is the wavelength? Homework Equations wavelength = (dsin\theta) / m y=Ltan\theta...
  8. J

    Does a single photon have a wavelength?

    I may be mixing things up terribly, but since the energy of a photon (or any particle for that matter) is related to its frequency, does a single photon have an associated wavelength and energy, or do those terms make sense only when considering a stream of particles?
  9. jaketodd

    Changing wavelength while preserving geometry?

    Are there ways to change the wavelength of an EM wave while still preserving all geometry of the wave (for instance, preserving an interference pattern which has, of course, irregular geometry in between the minima and maxima of the wave)? I've heard some crystals can change the wavelength but...
  10. B

    Photoelectric Effect - Wavelength of a Photon

    Homework Statement Calculate the wavelength of a photon having the same momentum as an electron moving at 1.0  106 m/s. The answer is supposed to be 0.73 nm. Homework Equations Ek = (m*v^2)/2 Ek = hf - W p = E/c = hf/c = h/\lambda The Attempt at a Solution I first found Ek using...
  11. P

    De Broglie Wavelength Equation

    Homework Statement What was the significance of the de Broglie equation? Homework Equations p = h/λ p = mv The Attempt at a Solution It says that not only do waves act as particles, transferring energy and momentum to matter only at localised points, but moving particles (e.g...
  12. E

    Wavelength in an electron transition

    1. Is a 4p -> 4s transition allowed in sodium? If so, what is the wavelength? If not, why not? (Z = 11 for sodium) 2. \Deltal = |l2 - l1| = 1 That is for the first question, in which case it is allowed, hence |0-1| = |-1| = 1, and meets the requirements for the equation. The second...
  13. L

    Why Don't We Convert Wavelength When Light Enters Glass?

    Homework Statement When 2 glass plates form an air wedge with a fine wire at one end, why don't we convert the given wavelength in air of light into the wavelength in glass since we have to convert it when it is entering in water?? Thanks Homework Equations The Attempt at a Solution
  14. M

    Maximum Wavelength of Photon - electron ejection

    I have worked on this problem for about an hour, looked through the book lots of times, and honestly just don't know how to get it done. So I am here with all you fellow physicists for help! :) Homework Statement X rays bombarding heavy atoms can be used to eject electrons from the 1s shell...
  15. L

    Wavelength Conversion in Water: 640 nm Light & Wedge

    Homework Statement Light of wavelength 640 nm in water illuminates a glass (n = 1.5) wedge submerged in water (n = 1.33). If the distance between successive bright fringes is 6 mm. Homework Equations The Attempt at a Solution I have a lot of trouble trying to convert the...
  16. S

    Is colour dependent on wavelength of frequency?

    EDIT: title should be Is colour dependent on wavelength or frequency Okay, and so here is the question in my mind. We all know (or at least taught) that when light enters an optically denser medium, it slows down and its wavelength shortens. Frequency, however, remains the same. Going by the...
  17. Y

    Wavelength and Diffraction

    I've been told that longer wavelengths are able to diffract more than short wavelengths. The hyperphysics page on sound wave diffraction also states this fact. Nothing I've read have explained why exactly longer wavelengths are able to diffract more than shorter wavelengths, so that's my...
  18. M

    De broglie wavelength and energy

    Homework Statement The potential-energy function U(x) has the constant value U_0 in the interval 0 < x < L and is zero outside this interval. An electron is moving past this square barrier, but the energy of the electron is greater than the barrier height. If E= 6 U_0, what is the ratio...
  19. R

    Discrepancy between Sun's radiated max wavelength and it's apparent color

    Homework Statement By Wien's we can determine that the max wavelength radiated by the sun is around 500 nm. How does this compare to the apparent color of the sun? Attempt to explain this discrepancy. Homework Equations lambda_max*T=2.9x10^-3 The Attempt at a Solution I said...
  20. S

    Wave Interference and wavelength

    Homework Statement In Fig. 17-35, sound with a 15.6 cm wavelength travels rightward from a source and through a tube that consists of a straight portion and a half-circle. Part of the sound wave travels through the half-circle and then rejoins the rest of the wave, which goes directly...
  21. S

    What is the Wavelength of an FM Radio Wave at 107.5 MHz?

    Homework Statement An FM station broadcasts at 107.5 MHz. What is the wavelength of this wave? Homework Equations well i know that speed = frequency X wavelenght but if i don't know the speed then how can i find the length The Attempt at a Solution so i found out that the average...
  22. M

    De Broglie wavelength question

    Homework Statement In one of the classes, a recent experiment showing the interference of C60 molecules using a double slit apparatus was discussed. (a) If the average velocity of the C60 molecules is v= 200 m/s, calculate the De Broglie wavelength for a C60 molecule Homework Equations...
  23. Y

    Question regarding particles and wavelength

    Homework Statement I know about particle/wave duality; however, when I read a passage and it says the wavelength of the particle I'm not sure what it's referring to. Is it the actual wavelength of the particle or the wavelength of the wavefunction for a particular eigenvalue? Homework...
  24. G

    What is the de Broglie wavelength of this electron?

    Homework Statement What is the de Broglie wavelength of this electron? Given is 500 eV Homework Equations KE= 1/2 mv^2 1 eV=1.602x19^-19 J The Attempt at a Solution I converted the 500 eV to 8.01x10^-17 via the given conversion. Now I'm stuck.
  25. A

    Find the wavelength of the sound.

    Two speakers , each producing a pure tone of 1000Hz, are separated by 4m and are placed against one wall of a 15m wide room. You walk along the opposite wall of the room and hear the locations of the maxima and minima interference patterns a.)Find the wavelength of the sound. b.)Find the...
  26. O

    How Can Resonance Experiment Accuracy Be Improved?

    Homework Statement I have carried out an experiment, placing tuning forks of different frequencies above a pipe in a cylinder of water to form a closed end pipe, and then recording the lengths at which resonance occurs, to find out fundamental frequecnies. Homework Equations I have...
  27. J

    Tension In musical strings and wavelength

    Homework Statement One string of a certain musical instrument is 79.0cm long and has a mass of 8.79g . It is being played in a room where the speed of sound is 344m/s . A)To what tension must you adjust the string so that, when vibrating in its second overtone, it produces sound of...
  28. J

    Find wavelength of pair producing photon

    Homework Statement i just have questions the one i couldn't figure it out the eletroc/position pair produce track drift chamber has field of 0.2 weber/m^2, radius of the drift 0.025m. using p = eBr equation to find the energy and wavelength of the pair producing photon. with the...
  29. J

    Find compton wavelength shift

    Homework Statement X-ray beam with wavelenth= 1 X 10-10m and a gamma-ray beam from a Cs137 sample with wavelength= 1.88 X 10-12m. If the radiation scattered form free electron is viewed at 90 deg to the incident beam a) What is the Compton wavelength shift in each case? b) What kinetic...
  30. X

    Frequency and wavelength on different instruments and loudness

    Homework Statement How does the frequency and wavelength alter between the same note played on an oboe and violin. And also what physical difference in the waves allows them to be played loudly or softly. Homework Equations The Attempt at a Solution For the oboe and violin part...
  31. J

    What is Bragg Detuning and How Does it Affect Bragg Gratings?

    Hi all, Could someone pls explain to me what is bragg detuning?...or some links explaining this phenomenon?
  32. G

    De Broglie Wavelength Derivation

    In Classical Mechanics the derivative of Kinetic energy with respect to velocity is momentum, so I was wondering if this is valid: In this L is lambda or wavelength and h is Planck's Constant. E=hf, therefore E=h(v/L) This means that dE/dv=h/L.(h and L are constants and the derivative of...
  33. M

    Relativistic De Broglie wavelength

    Homework Statement De Broglie wavelength What is the De Broglie wavelength of the 1.0-TeV (1TeV=1012eV) protons (mpc2=938.3MeV) accelerated at the Fermilab Tevatron accelerator? These high-energy protons are needed to probe elementary particles [Hint: You need to use relativistic formula, but...
  34. F

    What Happens to the de Broglie Wavelength as Mass Approaches Infinity?

    If, in the expression for the de Broglie wavelength, we let m -> infinity, do we get the classical result for matter? de Broglie wavelength = h/mv so as m goes to infinity the de Broglie wavelength goes to 0. So does this mean that particles with larger mass don't display wavelike...
  35. M

    DeBroglie Wavelength Comparison

    Homework Statement Compare the deBroglie wavelength for an electron in the n=6 orbit of He+ compared to the n=2 orbit. Is the deBroglie wavelength the same, smaller, or larger? Derive this. Homework Equations Quantization of Paths of Electrons: 2 pi r = n (lambda) Bohr Radius: rn=n2 aB The...
  36. D

    Light Wavelength increases over a distance

    The wavelength of light increases over large distances right? It seems that there is no account for this when determining the redshift of a distant star.
  37. S

    De broglie wavelength and orbits

    Homework Statement If the be Broglie wavelength associated to the first orbit of the electron inside the atom of hydrogen is 62.4 nm, what is the wavelength associated to the fourth orbit? 1. 62.4 nm 2. 124.8 nm 3. 312 nm 4. 249.6 nm Homework Equations # of...
  38. H

    What is the Wavelength of a Tuning Fork with 1000Hz Frequency?

    Homework Statement The problem asks to find the wavelength of a tuning fork with 1000Hz frequency. Then they give you two consecutive resonant lengths which are 25 cm and 76 cm. The way they measured the resonant lengths is by placing the tuning fork over a tube that has 1 end open and 1...
  39. Y

    Physics3, question on intensity, power, wavelength

    hi folks, here's another problem I've made a few incorrect guesses on. On my other post I may have not mentioned the potential for errors in using various SI units, but I think in general I'm careful enough so I'll continue to not worry about that in this post. So assume I know enough to...
  40. wirefree

    Human voice: Wavelength to frequency

    With reference to the formula: distance (wavelength) = k / frequency what does a wavelenght of 1176470.58 signify with regards to the fundamental frequency of a typical adult female being between 165 to 255 Hz, where d = 300/.000255 = 1176470.58 Would greatly appreciate advise...
  41. A

    What is the wavelength of the helium-neon laser beam in the unknown liquid?

    A helium-neon laser beam has a wavelength in air of 633nm. It takes 1.38 ns for the light to travel through 30cm of an unknown liquid. What is the wavelength of the laser beam in the liquid?
  42. S

    Solving Atom Ionization with a 50 nm Wavelength

    Homework Statement A hydrogen atom has an electron in the fundamental state. a. Show that a radiation with λ = 50 nm will ionize the atom. b. What will be the excess kinetic energy of the electron in joules? Round up your answer to the nearest hundredth. Homework Equations 1/lambda=...
  43. O

    How do you determine wavelength, x, from this expresstion?

    Homework Statement The problem is a semiconductor question which I have resolved and gotten the equation: w = (50.12 x) ^ 0.5 From the knowledge of this system, x is in an interval such that 0.5 < x < 2.5 What mathematical method of solution would help find the solution to this...
  44. P

    Calculating Wavelength of Surface Waves on a Lake

    Homework Statement it's stated that 2.5meters separated a trough and an adjacent crest of surfae wave on a lke. Homework Equations The Attempt at a Solution At first I thought if the trough to th crest is 2.5meters then i would double that to get the wavelenght from crest to...
  45. P

    Boat wavelength oscillation problem

    Homework Statement a father and son went on a cruise that's 20 ft long. the dad observed the cruise swayed thru 22 complete oscillations in 38 s, and one wave crest pass per/oscillation. the son noticed that each crest required 13s to reach land and the wavelenght is twice the length of the...
  46. P

    What is the formula for determining wavelength in different mediums?

    Please help! In my physics, I need to find the wavelengths of the waves from a source in a different medium. In the first medium, my angle of incidence is 35 degrees and with a speed of 150m/s and a frequency of 75Hz. In the different medium the speed has dropped to 96m/s. I know the...
  47. S

    Wavelength of carrier frequency radio signal

    Homework Statement Your favorite radio FM radio station broadcasts at a carrier frequency of 94.7 Megahertz. What is the wavelength of the carrier frequency radio signal? Homework Equations velocity=wavelength(frequency) The Attempt at a Solution 94.7x10^-6(w)= 3x10^8 w= 3.2...
  48. N

    Is a photon's wavelength relative to the velocity of its source?

    Is a photon's wavelength dependent on the velocity (or acceleration) of the atom which it was emitted? For example, if a photon is emitted from a stationary (or slow moving) molecule, then that molecule is accelerated. Will the photon's wavelength shift wrt to the acceleration (or...
  49. L

    Wavelength or amplitude < a Planick length?

    Is it possible for an object's size to be great enough to make it's wavelength or amplitude < a Planick length? If so, does it's position become certain, and, applying the uncertainty principle, can you not know the velocity?
  50. L

    Wavelength and resolution

    Hi there! What is meant by saying that a photon of smaller wavelength can resolve smaller distances? I know from scattering theory that the form factor is the Fourier transform of the charge distribution and that knowing the form factor at high momentum transfers gives a better overall picture...
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