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. L

    Maxwell's Equations - Wavelength Dependance derivation from Group Velocity

    Homework Statement For a particular Dieletric it is observed that over a range of frequencies, the group velocity varies exponetinally with wave number: v_{g}=ae^{bk} , where a,b are constants. *(PLease not that the superscript g on v on the LHS side is meant to be subscript, however it...
  2. A

    Wavelength with P/Q exponent equation-solve for P/Q

    Homework Statement Speed of an ocean wave depends on the wavelength \lambda in meters and gravitational field. (see equation below). Find values of P and Q. K is a constant and has no dimensions Homework Equations V = K\lambdaPgQ The Attempt at a Solution V=velocity, which is...
  3. Q

    Why does glass not permit long wavelength infrared to pass through?

    Why does glass not permit long wavelength infrared to pass through?
  4. P

    Question regarding de Broglie wavelength.

    Hi there, Is it possible if an object were to hypothetically gain enough momentum such that its de Broglie wavelength is equivalent to, say, some light in the visible spectrum, that the object would emit light? Thanks!
  5. P

    Interference at a single wavelength

    Homework Statement I have a question relating to the interference at a single frequency? Does this statement mean that the intereference has occurred between two waves which are completely in phase? I also have a question regarding if two waves which are not in phase but do not cause...
  6. G

    What is the wavelength of an object at rest according to de Broglie's equation?

    if de Broglie's equation: wavelength = h/(mv) works allways, then what is the wavelength of an object at rest (v=0) is it undefined or infinity or something?
  7. M

    What do we mean by 'wavelength'

    hi everybody In sound waves or EM waves .. What do we mean by saying 'wavelength' ! physically I mean , Is that related to the size of the photon for example ( In EM ) ? Help me to understand
  8. H

    Matter wavelength and indeterminate of location and energy

    I have to find matter wavelength and indeterminate of location and energy for hydrogen particle which is in gas with konwn p, V, T I'm sorry for my english skills:P pressure will be p_{g} \lambda = \frac{h}{p} p = mv v = \sqrt{\frac{3p_{g}}{\varrho}} \varrho = \frac{n\mu}{V}...
  9. M

    Finding Wavelength: Solving with Frequency and Length

    Homework Statement i'm doing a lab and i have a chart which requires me to find the wavelength. The chart looks like this: Frequency(f) Period (T) Length (l) Wavelength (lambda) 512 ? .15...
  10. S

    Find the Frequency of Infrared Radiation with Wavelength 160.432 µm

    Homework Statement What is the frequency (in Hz) of infared radiation that has a wavelength of 160.432 micrometers? The speed of light is 3.00 x 108 m/s. Homework Equations Speed of light = wavelength x frequency Speed of light = 3.00 x 10^8 m/s The Attempt at a Solution I know that the...
  11. D

    Find Wavelength of Standing Wave in 200 cm String: Get Help Now

    A standing wave is set up in a 200 cm string fixed at both ends. The string vibrates in 5 distinct segments when driven by a 120 Hz source. What is the wavelength? * 10 cm * 20 cm * 40 cm * 80 cm I need some help with this problem. I can't seem to find anything with an equation or any...
  12. D

    Help Needed: Wave Frequency & Wavelength vs. Air Temp

    A sound wave in air has a frequency of 500 Hz and a wavelength of .68 m. What is the air temperature? * -18 degrees C * 0 degrees C * 15 degrees C * 27 degrees CI can't find an equation for this, and I don't know how to solve it. Anyone know anything about this? Please help me. Thanks.
  13. C

    Light, dielectric medium, c, wavelength

    What is happening to a ray of light of a certain wavelength that passes through a transparent dielectric medium? Ex: Green light enters in a Bose–Einstein condensate, and slows down some. Than the light is coming out of the medium in free space. What will be the speed of the ray light and...
  14. O

    Calculating Wavelength of Laser Diffracted by Slit Patterns

    Homework Statement I am to calculated the wavelength of the laser I shone through different slit patterns to create diffraction patters on a screen. For the single slit diffraction, Data: xm is the distance from the central image to the mth minimum. x1 0.008 x2 0.015 x3 0.023 x4...
  15. N

    Electron frequency and wavelength

    Hi, I'm studying the wave nature of particles. My book says that the de broglie wavelength of an electron is h / momentum, or h / (mv). I also have that E = hf = momentum2/(2m) = 1/2 mv2. I know that for a photon the frequency is speed of light / wavelength. I'm wondering why the...
  16. R

    Finding frequency & wavelength

    Homework Statement Find the frequencies and wavelengths (in air) of these notes. A(440.0 Hz) C(523.3 Hz) the given frequencies are not the answers Homework Equations velocity=frequency*wavelength The Attempt at a Solution 343m/s=440Hz/wavelength wavelength=.780 m this isn't...
  17. M

    Question on wavelength using the two slit experiment

    Homework Statement Red light with wavelength of 700 nm is passed through a two slit apparatus. At the same time, monochromatic visible light with another wavelength passed through the same apparatus. As a result most of the pattern that appears on the screen is a mixture of two colors...
  18. S

    Finding the wavelength and frequency

    Homework Statement A sound source is moving at 80 m/s toward a stationary listener that is standing in still air. The source emits sound at a frequency of 200Hz. Assume that the sound travels at still air at 343 m/s. 1. The wavelength of the sound in the region between the source and the...
  19. T

    Convert between Intensity as f'n of wavelength and intencity as f'n of frequency

    Homework Statement Bλ(T) = β Bν(T) / λ2 v = frequency λ = wavelength find β , if Bλ(T) is in units Watt/m2/μm while Bν(T) is in units Jy (= 10−26 Watt/m2/Hz) Homework Equations The Attempt at a Solution I know that first of all Bλ(T) = Bν(T) * |dv/dλ| = Bv(T) * c / λ^2 so...
  20. C

    How Small Can Accelerators Detect Particles?

    Homework Statement the wavelength of the probing beam must be approximately the same as the size of objects we want to resolve. For each of the accelerators described below, determine the smallest size objects that are resolvable and name an object roughly that small, remembering that these...
  21. P

    Relationship Between Energy and Wavelength

    I'm looking at the equations E=h\nu and \lambda=h/p and trying to determine the relationship between E and \lambda. What I'm coming up with is E=\lambda\nup, which simplifies to E=cp. This doesn't quite make sense to me though, is there a mistake, or should I just look more into the units of...
  22. J

    Light velocity, wavelength, and frequency

    Just a quick concept check. I was asked that as light travels between two media, what happens to its frequency, wavelength and velocity. I want to say that the frequency remains the same while the velocity and wavelength change, based on the difference of the index of refraction between...
  23. K

    Calculate wavelength in pm associated with electron traveling 60% of the speed of lig

    Homework Statement Calculate the wavelength, in picometers, associated with an electron traveling 60.0% of the speed of light. Homework Equations Wavelength = h / (mv) The Attempt at a Solution I know the h value. The v value I believe it is 60.0% of 3.00 x 10^8 But what is the m value...
  24. PrincePhoenix

    Why does the absorption of EM radiation vary with wavelength?

    Why does penetration increase with decrease in wavelength?
  25. L

    Finding (1) wavelength, and (2) thickness of film for constructive interference

    1) In a double-slit experiment, two parallel slits are illuminated first by light of wavelength 460nm, and then by light of unknown wavelength. The third-order (m = 3) dark fringe resulting from the known wavelength of light falls in the same place on the screen as the second-order (m = 2)...
  26. W

    Finding Wavelength and Velocity of an Ocean Wave.

    Homework Statement Find Wavelength and Velocity of an Ocean Wave. Known Variables: Water Depth=300m Frequency=8secs Amplitude=3m Homework Equations Wavelength (m) X Frequency (s-1) = velocity (m/s) v=velocity The Attempt at a Solution I have 2 missing variables for both...
  27. Z

    Minimum Wavelength of Electron Accelerated in TV at 30,000 V

    Homework Statement In a television, an electron is accelerated through a potential difference of 30,000 V. What is the minimum wavelength produced. Homework Equations E = qv E = hf The Attempt at a Solution I figured that we should first find total energy. E = qv => E = (1 x...
  28. J

    Wavelength limits of the Lyman and Paschen series of Hydrogen

    Homework Statement Use the Bohr theory to find the series wavelength limits of the Lyman and Paschen series of hydrogen. Homework Equations \lambda=\lambdalimit(n2)/(n2-n02) Lyman: n0=1 Paschen: n0=3 The Attempt at a Solution The solutions are 91.13 nm (Lyman) and 820.1 nm...
  29. B

    Photoelectric effect wavelength

    This is not a specific question; I'm just unclear about a concept. Homework Statement Given the kinetic energy of an electron emitted, how would you find the wavelength? Homework Equations E=h*frequency or E=0.5mv2 The Attempt at a Solution I'm thinking I would use the...
  30. G

    Expressing a wavelength equation in linear form; k must be determined via slope

    Homework Statement How should the variables ( l and T) be plotted to obtain k from the slope of a linear graph? Identify (write out) the constants correstponding to the slope and intercept of the linear graph. Homework Equations l = lambda l = (k/f)*(T/u)^0.5 The Attempt at a...
  31. S

    Minimum wavelength when electrons strike phospor

    Homework Statement Assume electrons are accelerated through a potential difference of 20000 V inside a TV picture tube. What is the minimum wavelength that could be produced when the electrons strike the phosphor? Homework Equations W = qV The Attempt at a Solution I use the...
  32. B

    Mass of a planet given wavelength of an orbiting craft?

    Problem: Suppose a spacecraft is in a circular orbit about a distant planet. The spacecraft emits a continuous radio signal with a wavelength of 6 m. You observe the signal's wavelength to vary between 5:99969 m and 6:00031 m; the period of variation (i.e., the full period of the signal) is...
  33. M

    Calculate the wavelength for red light

    Homework Statement The frequency of red light is 430THz calculate its wave length. Is the answer below correct? Homework Equations (3*10^8) / (430*10^12) = wave length The Attempt at a Solution (3*10^8) / (430*10^12) = 6.98 to 1 Decimal Place
  34. LarryS

    Wavelength Less Than Planck Length?

    It seems like if you accelerated a massive particle to a high enough velocity (momentum), you could get it's wavelength to be less than the Planck Length. Does that make sense? As always, thanks in advance.
  35. S

    Wavelength in QM: Definition & Measurement

    Can anyone tell me how is wavelength defined for a wave associated with a particle? If the wave function we are speaking of has no physical significance,then how can measure its length? tks for any rpl
  36. K

    Calculating Wavelength of Photons to Produce 30 keV Electrons

    Homework Statement 56. What wavelength of photons are needed to produce 30 keV electrons in a compton scattering? Homework Equations E=\frac{hc}{\lambda} The Attempt at a Solution This question throws me off because I was under the impression that compton scattering didn't produce...
  37. P

    How Do You Calculate the Frequency of Radio Waves with a Wavelength of 100mm?

    the speed of sound in air is 330ms^-1 , speed of light is 3 x10^8 ms^-1... what's the frequency of radio waves of wavelength 100mm ?
  38. C

    Wavelength -> antenna, waveguides, mirrors ets

    Hi I have this question for sometime, and until i found a recent post here on this forum (wavelength and aperture) i thought i was the only person who just plain didn't get it. My questions arises firstly when i consider antennae and as roughly quote from the many texts i have read "to...
  39. S

    De Broglie Wavelength - How does this hold for slow objects?

    OK so you get to the matter wave equation 'lambda = h / p' using E=cp - which describes the energy for massless particles. I can understand this holding for when cp>>mc^2 , but not for when the mc^2 is comparible. Any help?
  40. M

    Exploring Electron Scattering and Compton Wavelength Shifts

    Hi, I have a question regarding the Electron scattering angel Teta in formula in: http://www.whfreeman.com/MODPHYSICS/PDF/3-2bw.pdf which indicates Compton wavelength shift by: labda2 - lamda1 = (h/mc)(1 - cos(Teta)). (3.40) With Teta = 0 we get labda2 = lamda1 (no change of energy by the...
  41. E

    Photon wavelength quantization?

    Are photon wavelengths quantizised? If so, what are their possible wavelengths? Do their possible wavelengths also depend on the system they are in?
  42. R

    Calculation of wavelength of EMW produced due to an accelerated charged particle

    if an electron is accelerated by 2eV energy. then what will be the wavelength of emw produced? can we use E=hc/wavelength here? should we use always de broglie hypothesis for this? what will be the difference between wavelength of electron and wavelength of emw? are they same or not?
  43. S

    Wavelength Ratios for a Pitching Boat in a Deep Lake

    Homework Statement It is known that a water wave in a lake produced by the pitching of a boat at anchor with a pitching period T propagates with a speed bT ( b > 0) if the lake is deep enough and the water is at rest. Assume that a boat moves at a slow constant speed Vo with a pitching period...
  44. T

    Wavelength versus hole diameter

    Why does the wavelength of light have to be longer (or shorter?) than a hole diameter to pass through the hole? Also, is this phenomenon the same reason AM radio signals cannot be picked up as well FM radio signals when driving under an overpass?
  45. B

    DeBroglie wavelength for particle at rest

    lambda = h/mv v -> 0 means lambda is -> infinite? So if I have an old pickup truck that moves really slow, its matter wave is huge, right?? So it's now a wave and not a particle?
  46. T

    > Wavelength range of Hydrocarbon spectral emissions

    I was checking the NIST site with their Hydrocarbon line database search utility, and the frequencies of the lines for CH, CH2, and CH4 are on the order of 10^11 Hz approximately. That leads to wavelengths that are much larger than the visible region. Am I reading the search results...
  47. K

    Finding the Longest Wavelength of Standing Waves on a 254.0 cm String

    Homework Statement What is the longest wavelength for standing waves on a 254.0 cm long string that is fixed at both ends? Homework Equations The Attempt at a Solution When x = L (length of string): k(n) = n*pi / L wavelength (n) = n*pi / k(n) I got the answer, I just...
  48. L

    Calculating the wavelength of soundwaves

    Homework Statement Two speakers connected to the same source of fixed frequency are placed 2m apart in a box.A sensitive microphone placed at a distance of 4m from their midpoint along the perpendicular bisector shows maximum response. The box is slowly rotated until the speakers are in...
  49. J

    Wavelength of an electron homework

    Homework Statement -Electron has 3.00 MeV (or 4.8*10^-13 Joules) -it's relativistic -finding λ. Homework Equations h=6.63*10^-34 λ=h/p (obviously) And I'm not sure if they're needed, but the relativistic eq's are: KE = mc^2/sqrt(1-(v/c)^2) p = mv/sqrt(1-(v/c)^2)...
  50. J

    De Broglie wavelength (relativistic e-)

    Wavelength of an electron Homework Statement -Electron has 3.00 MeV (or 4.8*10^-13 Joules) -it's relativistic -finding λ. Homework Equations h=6.63*10^-34 λ=h/p (obviously) And I'm not sure if they're needed, but the relativistic eq's are: KE = mc^2/sqrt(1-(v/c)^2)...
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