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. Q

    How exactly does light's wavelength expanding over time mean space expands?

    I already understand the notion, but what I don't get is how that leap is actually logical. Wouldn't you have to assume the photons and atoms are somehow "attached" to the fabric of space? It seems like the same thing as saying Earth's atmosphere is attached to it's crust.
  2. vhbelvadi

    Number of Photons and wavelength?

    I read recently that the "number of photons emitted by a charged particle is inversely proportional to wavelength" with regard to Cerenkov radiations. (The wavelength refers to the radiation which is of comparatively shorter wavelength, towards the blue-end.) I was looking for a more detailed...
  3. N

    Free Spectral Range in wavelength

    Homework Statement Hi The FSR of a laser with length L is given by Δv = c/2L. If I want to find what Δv is in wavelength, then how do I do this? Obviously I need c=vλ, from which we know that Δv/v = Δλ/λ. But the last equation I can't apply to this case, since it refers to errors around...
  4. Z

    Why is resolving limited by wavelength?

    Hi! This might very well be a silly question. In many courses I've been presented as an obvious fact that it won't work to use (e.g.) light with a wavelength larger (at least, not much larger) than the thing you want to resolve. Why is this exactly? Thinking of photons I could find no...
  5. N

    Converting between Wavelength and Frequency in Resonators

    Homework Statement Hi Say I have an energy level centered around λ with some linewidth Δλ, and I wish to find the corresponding frequency linewidth Δν. What I would use is the following relation Δλ/λ = Δν/ν. Is this correct? Thanks in advance. Niles.
  6. B

    Calculating the wavelength of an electron

    Homework Statement Calculate the wavelength of a beta particle (electron) that has an energy of 4.35 × 104 eV Homework Equations E = hf λ = h/mv V = W/q eV = .5mv^2 The Attempt at a Solution I can't figure out how to get electron volts into a form of energy that I'm familiar...
  7. J

    Wavelength Speed Question

    Radio waves travel at the speed of light. A satellite is in a "geosynchronous orbit." A radio signal is sent from the ground to the satellite and then the satellite sends the signal back down to the ground. Satellites in geosynchronous orbit are 36,000km above the surface of the earth. How much...
  8. H

    Spacetime expansion effects on wavelength of travelling light

    Hello, Do current theories of cosmological expansion take into account the effects expanding space would have on a beam of light traveling through space? i.e. if an expanding medium of gas with constant pressure decreases the temperature/velocity of particles, would an expanding medium of...
  9. E

    How to find the right material to change the wavelength of light?

    Hello all, I'm working on a personal design problem and am stuck. I am trying to figure out "how to figure out" what material I would need. I hope that makes sense.For example: I have light of 400nm and I want to change it to light of 500nm. I figured I could just pass the light through a...
  10. F

    Calculating Wave Speed for a 6m Rope with 7kg Mass and 140 N Force

    Homework Statement A 6m length of rope has a mass of 7kg. It is pulled taut with a force of 140 N. What is the speed of the wave for the rope? Homework Equations i have no idea... v=λf L=λ/2 The Attempt at a Solution I have no idea if I have the right formulas...
  11. H

    Resonant wavelength of a cavity resonator using different internal materials?

    Hello everyone, Recently I have been studying cavity resonators. I noticed that all cavity resonators have air in them, but I was wondering what the effects would be if something other than air was used? For the sake of simplicity let's say we put a dielectric material in it with a...
  12. A

    Wavelength and precision of observation

    I don't understand why when you make an observation, you need a wavelength shorter than the wanted precision. i.e. you can't make clear pictures of golf balls with radio waves, you can't observe things smaller than a photon with an optical microscope.
  13. H

    Young Double Slit Experiment (Determine wavelength of light source)

    Homework Statement Upon using Thomas Young's double slit experiment to obtain measurements, the following data was obtained. Use this data to determine the wavelength of light being used to create the interference pattern. DO this in 3 different ways! The Angle to the Eighth maximum is 1.12...
  14. N

    Quarter Wavelength Transmission Line

    An open-ended quarter-wavelength, air-spaced, parallel-wire transmission line is found to be in resonance with an oscillator when its length is 0.25 m. When a capacitance of 1 pF is connected across the open end, it is found that the length of the line must be reduced to 0.125 m to obtain...
  15. C

    Calculate Wavelength from Rydberg's Constant

    Wavelength HELP! Homework Statement Calculate the wavenumber (v=1/lambda) and the wavelength of the first transition in the visible region of the atomic spectrum of hydrogen. I KNOW THE ANSWER... 656.3 nm. I just don't have a clue how they got that answer, I do know that I had to use...
  16. W

    How Does Electron Kinetic Energy Compare to Hydrogen's Ground State?

    Homework Statement An electron has a de Broglie wavelength equal to the diameter of a hydrogen atom in its ground state. What is the kinetic energy of the electron? How does this energy compare with the ground-state energy of the hydrogen atom? Homework Equations λ = h /mv...
  17. B

    How to derive characteristic wavelength of x-ray from energy equation?

    Hello. first, sorry for my poor English. Derive characteristic wavelength from radiation powerThis is radiated power from bending magnet (synchrotron storage ring accelerating electron to get x-ray) and these are wave distribution from storage ring and what I have to derive is as follows...
  18. E

    De Broglie Wavelength: Practical Applications in Life

    i want to know the practical application of De Broglie wavelength in the life !
  19. P

    A 50cm wavelength EM wave in air has 50mW/m^2 of energy.

    Homework Statement A 50cm wavelength EM wave in air has 50mW/m^2 of energy. what is the frequency? what is the average E field? What is the B field strength? What would be the λ in water? Homework Equations I found the λ. How do I find it in water The Attempt at a Solution...
  20. R

    Calculating Electron Wavelength from Quantum Levels Using Orbit Circumference

    I know that λ=h/p, but how do you find the wavelength of electrons from different quantum levels using the circumference of the electron's orbit?
  21. J

    Finding wavelength and wave speed in a sinusoidal wave.

    Homework Statement A sinusoidal wave is propagating along a stretched string that lies along the x-axis. The displacement of the string as a function of time is graphed in the figure (attachment) for particles at x=0m and x=0.0900m. (A) What is the amplitude of the wave? 4mm (B) What is the...
  22. A

    De Broglie wavelength, kinetic energy

    Homework Statement (a) Find the kinetic energy of an electron whose de Broglie wavelength is equal to 0.63 Å, a typical atomic size. Ke = 379 eV (b) Repeat part (a) for an electron with a wavelength equal to 1.7 x 10-15 m, a typical nuclear size. Ke = _____eV Homework Equations...
  23. K

    Doppler Effect + Wavelength problem

    Homework Statement A sound source emits sounds of frequency 210 Hz that travel through still air at 340 m/s. The listener moves at 85 m/s relative to still air toward the stationary source. What is the wavelength of the sound between the source and the listener? Homework Equations f' = f[1+...
  24. E

    Is the maximum wavelength of light bounded by the size of the universe?

    First, is one light wave (or perhaps half wave) possible that stretches across the universe, such that each end of the wave (or half wave) is on opposite sides of the event horizon of the universe, which is the distance light has traveled since the beginning of the universe. Second, is this...
  25. Y

    When wavelength is smaller than 1pm

    Hi all, Higher end of electromagnetic spectrum is γ rays around 1pm (300EHz). What are the characteristics of frequencies having smaller wavelength than γ rays ? What are the characteristics of signals that has wavelength at Planck scale?
  26. S

    Understanding De Broeglie Wavelength & Electron Orbits

    Electrons orbits are only allowed when a stable standing wave is formed around the nucleus, i.e. when the orbit circumference is an integer multiple of the electron's de broeglie wavelength. But is it possibly for it to temporarily exist in an orbit that is NOT an integer multiple of its...
  27. J

    Calculating De Broglie Wavelength in Bohr Model

    Homework Statement In the Bohr model of the hydrogen atom, if the electron is in the second orbit with a radius of 2.12 Å. What is the de Broglie wavelength of the electron? Homework Equations λ = 4h^2ε/me^2 The Attempt at a Solution I found this equation hunting around online and...
  28. P

    LED specific voltage for specific wavelength

    Hello I am trying to design a precise circuit for LEDs. I have a datasheet from a manufacturer and it says an LED is capable of running 3.0v at 640nm and 3.4v at 660nm. Is there a way to tailor the power (voltage) so that the LED will run exactly or at least approximately at 3.0v or 3.4v...
  29. A

    Calculating Error In Wavelength

    Homework Statement I am unsure whether I am calculating the error correctly for the wavelength given that x=14.3,15.3,16.2,17.1,23.3 all in degrees Homework Equations \lambda=d*Sin(x) where d is my slit size in meters \frac {1}{600000} x=measured angle \delta x= 0.1 degrees...
  30. T

    Combining SR and the Broglie Wavelength equations: Are they cumulative?

    I don't think this would ever come up on any of my tests in high school, but how would one answer a question combining the Broglie Wavelength of a particle and Special relativity? Are they cumulative? BW : λ= h/mv
  31. M

    Nodes, Antinodes, wavelength

    Homework Statement If you go any node in a standing wave to the next adjoining antinode, how many wavelengths have you gone? Homework Equations The Attempt at a Solution
  32. T

    What is the kinetic energy of particles with a de Broglie wavelength of 0.50 nm?

    Find the kinetic energy of the following particles that each have a de Broglie wavelength of 0.50 nm.? (a) photons ____eV = 2480eV (b) electrons ____eV (c) neutrons ____eV (d) α particles ____eV i know E= hc/wavelength which = a and after that I am stuck i know that the wavelength =...
  33. J

    Can you change the wavelength of light without disorting its path?

    If I had a photon with 450nm wavelength, purple. Could I change it to become a radio wave? without it going in another direction or anything.
  34. A

    Interpretation of De Broglie's wavelength ( matter wave ) for macro objects?

    The De Broglie's wavelength is given by λ = h / mv h = 6.626 x 10^(-34) Js Now, if a macro-object of 6.626 kg is moving at a speed of 10^(-34) m/s then its De Broglie's wavelength comes out to be 1 meter (metre). What does it mean to have 1 meter wavelength for that object? If another object...
  35. S

    How to find the wavelength of a sound wave?

    Homework Statement What is the wavelength of a 25 Hz sound wave? What is the wavelength of a 4.5 kHz sound wave? Homework Equations wavelength = velocity / frequency or λ = v/f The Attempt at a Solution I know that I'm supposed to plug the 25 into the equation, but he didn't give...
  36. M

    De broglie wavelength for ordinary objects.

    Hello there, If an object has a mass of 1 in arbitary units, and it's velocity is zero relative to you, what is the de Broglie wavelength? Shouldn't p be zero in this case? Or am I missing something related to intrinsic energy and momentum? Thank you very much.
  37. J

    Theoretical Particles @ Planck Scale: Is there a maximum wavelength of light?

    First time poster so please be gentle... E = h * f f = c / wavelength 1) Is there a theoretical limit on maximum f (minimum wavelength of Planck length)? 2) Is there a theoretical limit on minimum f of 1 (maximum wavelength of c)? (ie// the maximum distance that a photon can cover in...
  38. S

    Calculating energy from flux and max wavelength

    hey I am calculating energy of a blackbody emitter, and i have the flux (energy per unit area) and the peak wavelength emitted. how do i calculate total energy?
  39. A

    Grade 11 Physics: WAVES. Finding Wavelength & Frequency

    I missed the day where we were taught the formulas for frequency & wavelength, so doing the questions below are a struggle. Please someone explain how . Question 1 (wavelength) : The speed of sound in air at room temperature is 343m/s. The sound wave produced by striking middle C on a...
  40. A

    Determining Neutron Wavelength with mass alone

    Homework Statement Consider a particle of mass m in the potential V(z)=mgz z>0, infinity if z<0 Show that the wavelength of a neutron (m~1000MeV/c^2) is on the order of 10um. Homework Equations p=(2m(E-mgz))1/2 \lambda=h/p The Attempt at a Solution The most direct solution...
  41. T

    Wavelength in finite potential well

    Homework Statement 1)The graph below represents the ground state wave function of an electron in a finite square well potential of width L. The potential is zero at x = 0. The wave function of the electron within the well is of the form A cos( 2πx / λ ) where A is a normalization...
  42. P

    Using Light to Make Processors with Features Smaller than It's Wavelength?

    I've been reading up on photolithography trying to understand how processors with sub-wavelength features can be made through photolithography, but I just don't get it. Can someone please help me by explaining in a conceptual way how light with a wavelength of, say, 200nm can be used to make...
  43. M

    Wavelength sand refractive index

    why do refractive index vary with the wavelength?what makes the relation between wavelength and the refractive index reverse relation??and what makes the relation between frequency and wave length direct relation??does it has somethin to do with energy and the abiliy to penetrate bodies??Are...
  44. E

    What multiplicative factor does speed and wavelength change by?

    Consider a wave on a string with constant tension. If the frequency of the wave is doubled, by what multiplicative factor does a) the speed and b) the wavelength change? I don't really know how to begin to answer this question. The best i could think of is using v=wavelenght x f and then...
  45. V

    Calculating de Broglie Wavelength & Double-Slit Fringe Width

    Homework Statement Find the de Broglie wavelength for an electron with v=0.001c. Find the angular width of the central bright fringe in a double slit experiment, with the separation of the two slits d=50nm. Homework Equations wavelength = h/mv d sin(theta)=n*wavelength The...
  46. N

    Spatial Resolution calculation using wavelength (medical imaging)

    Hi Im comparing PET scans and MRI scans and I've noticed that MRI s spatial resolution is 0.3-1mm while PET scans have a spatial resolution much larger, around 5-7mm. I was just wondering how these figures are calculated. I've looked up some formulae and all I could find was wikipedia...
  47. F

    Determine electronic transitions by the emitted wavelength?

    Homework Statement What is the electronic transition of He II when it emits 468.6 nm photon.Homework Equations \frac{1}{\lambda}=4R\left(\frac{1}{m^2}-\frac{1}{n^2}\right)The Attempt at a Solution I know it is a pashen-alpha line from googling but I don't know how to find that from this...
  48. P

    Does Light Really Have a Wavelength?

    I'm curious as to how we know the wavelength of light. Correct me if I'm wrong, but my understanding of light is that it is traveling variations/vibrations in the electromagnetic field, as such it has a speed and a frequency, and therefore a wavelength...but since light isn't really a little...
  49. J

    DeBroglie wavelength, kE to (p) conversion?

    I have a relatively simple question. I should know this, but... I need to solve for the deBroglie wavelength when only the kinetic energy is known. Shouldn't I be able to convert kE to momentum (p), when the object does not have a known velocity or mass...? Much thanks... JD
  50. A

    DeBroglie wavelength and nucleon velocity

    Homework Statement Atomic nucleus consists of nucleons. What velocity (order of magnitude estimate) will a nucleon have inside a nucleus? Homework Equations \lambda = h/mv v = h/m\lambda The Attempt at a Solution The wavelength of a nucleus is on the order of 10^-15/m...
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