Wavelength Definition and 1000 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. 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...
  2. 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...
  3. G

    Free electron laser weapon -- operating wavelength for the US navy's 1MW FEL?

    I know fel operate a wide range of wavelengths, but does anyone know the main operating wavelength for the US navy's 1MW fel?
  4. M

    Determine the change in path length

    Homework Statement A ripple tank is setup and a point selected on the second nodal line. determine the change in path length from two wave sources if they are in phase and separated by 2cm and the wave length is 5cm Homework Equations not really sure of what equations to use? The Attempt at a...
  5. T

    Observing wavelength at an angle

    I recently came across an equation stating that ## \lambda_{ob} = \frac{\lambda}{cos(\alpha)} ## if ##\alpha## is the angle the observer is relative to the wave's direction of propagation. I guess I can kind of understand that a person perpendicular (i.e. ##\alpha = 1##) would see the normal...
  6. N

    Do X-rays' wavelength or frequency help them not excite electons....

    ... to transmit through opaque objects.? So when it comes to bone the x-rays cannot pass through them, or the steel plate because, the energy is higher, and or those bones, and steel plate have more electrons in their shells, and so is it the more electrons that absorb the X-rays, or is it the...
  7. S

    Find wavelength, frequency and speed of a wave,

    So I was given this diagram to a wave of a rope. the following questions i have to answer... 1) Find the wavelength in metres. 2) If the time that the wave takes to move from point X to point Y is 6.0 s, determine the speed of the wave and its frequency 3)Find the speed and wavelength if the...
  8. D

    Classical Wavelength, frequency, and radar

    I'm doing a high school paper on the effects of frequency alterations on a radar image. Can someone recommend a book which I can use?
  9. D

    Electron and wavelength problem

    Homework Statement Electron on n=6 level emits wavelength of 410.2nm. What energy level does it move too? Homework Equations 1/L = R ( 1/N^2 - 1/n^2) where N is initial and n final R=1.096779*10^7 m The Attempt at a Solution 1/410.2 = 10967790 (1/36 - 1/n^2) 1/4498975152 = (1/36 - 1/n^2)...
  10. CMATT

    Wave Speed & Wavelength of Harmonic Oscillation on Slinky

    (a) A wave traveling on a Slinky® that is stretched to 4.5 m takes 2.6 s to travel the length of the Slinky and back again. What is the speed of the wave? For this one, I did v = d/t = 4.5 m / 2.6 s = 1.73 m/s Then I did v = (1.73)(2) = 3.46 m/s This is correct (b) Using the same Slinky...
  11. Mighalo

    Determine the wavelength of the scattered photon

    Homework Statement In a Compton scattering experiment, a photon is scattered through an angle of 90.0deg, and the electron is scattered through an angle of 18.3deg. Determine the wavelength of the scattered photon 2. Relevant equation The Attempt at a Solution [/B]I'm confused. I...
  12. A

    If n is infinity, wavelength is equal to what?

    in the dispersion relation of the surface plasmon the wavelength is proportional to square root of n. according to equation 5 in this paper: https://Newton.ex.ac.uk/research/emag/pubs/pdf/Barnes_JOA_2006.pdf if n goes to infinity, then what will be the value of wavelength. Thank you
  13. K

    How do I solve for the wavelength of an alpha particle?

    Homework Statement Compare 25-MeV alpha particles wavelengths with the size of a nucleon in a nucleus. Homework Equations λ = h/p E2 = p2c2 + m2c4 KE = ½mv2 p = mv The Attempt at a Solution To compare the wavelength of an α particle with a nucleon, I would need to divide the wavelength of...
  14. Jeprox

    Light, wavelength and optical filters

    Hi, I have read from previous topic regarding color of light vs wavelength. It is a bit confusing for on my self as I do not have any background on this. Hopefully someone could chime in and educate myself. Here it goes, it has been lingering in my head that the color of light emitted by a...
  15. H

    Light's Color Change in Different Media

    if a ray of monochromatic light comes from a denser medium to a rarer medium does the color reaching a viewer in the rarer medium differ from the actual color of light in the denser medium (as wavelength of light is different for both the media)?
  16. Phynos

    De Broglie Wavelength for 1Mev electron

    Homework Statement Calculate the de Broglie Wavelength of a 1 MeV electron. Express your answer in femptometers. Homework Equations ## λ = h/p ## ## p = (2mT + T^2/c^2)^{1/2} ## The Attempt at a Solution basically just plugged everything in. ## λ = \frac{h}{(2mT + T^2/c^2)^{1/2}} ## ## λ...
  17. C

    Hydrogen Emission Spectrum, Electrons, and Quantized Energy

    I understand that the result of the hydrogen emission spectrum experiment was that only certain wavelengths of light were emitted and that led to the conclusion that electrons emit light when they relax and that they absorb light when they get excited. How does that prove that the energy for...
  18. Sterling Lutes

    Amount of single photons to make white light?

    First off I hope I'm putting this in the correct forum. My question is more than just the minimum amount of photons to make a single blip of white light, but more so the base photons in the visible spectrum of light. We have all seen a prism split light into violet, blue, cyan, green, yellow...
  19. I

    Relativistic Calculations for De-Broglie Wavelength

    Homework Statement At what energy will a non-relativistic calculation of the De Broglie wavelength of an electron be in error by 5%? What is this energy for a proton? Comment on your results. Homework Equations I have two (seemed to be) logical answers for this question, but with different...
  20. N

    How does Band Gap and Refractive index relate to Wavelength?

    Homework Statement Nobel prize for physics for blue laser diode using Gallium Nitride with band gap of 3.4 eV and a refractive index of 2.429. Explain how these parameters determine at what wavelength a Gallium Nitride semiconductor will laser at. Homework Equations E=\frac{hc}{\lambda}...
  21. B

    How Is the Longest Wavelength of Light Determined for Anti-Reflective Coatings?

    Homework Statement A sheet of glass (nglass = 1.5) is coated with a 95.6-nm-thick layer of magnesium fluoride (ncoating = 1.38) to prevent reflection in the visible spectrum. Assume the incoming light is normal to the surface. What is the longest wavelength of light strongly reflected from this...
  22. J

    Diffraction and Wavelength Dependency

    I have found lots of forum threads on this but I still can't see the connection between wavelength and diffraction. Here is a picture I found: If you increase the wavelength then all is this will do is just increase the time between the crests that arrive and I don't see how that can have...
  23. as123

    Homework -- wavelength associated with a neutron moving with energy of 2ev

    Homework Statement Calculate the de - Broglie wavelength associated with a neutron moving with energy of 2ev .( mass of proton mp= 1.67*10^-27 kg ) Homework Equations Wavelength= nh/ 2π KE = eVs = 1/ 2mv^2 eVs=hf Wavelength= v*f The Attempt at a Solution To calculate the wavelength at first...
  24. E

    Physics peak wavelength and temperature

    Homework Statement The peak intensity of light from the sun occurs at a wavelength 500nm. Astronomers discover a nearby star X which is the same size and mass as the sun, but has a peak wavelength of half this value. Is X hotter or colder than the sun and by how much?[/B]Homework Equations...
  25. C

    De Broglie wavelength of a train

    Homework Statement Imagine you are traveling in a train, and see in the distance how the train path splits into two parallel tracks separated by a distance d.1) Obtain an analytical expression of the de Broglie wavelength of the train. 2) What condition would you use to determine at what point...
  26. S

    How to find wavelength of wave?

    Homework Statement A backyard pool is 14.5 m long. For fun Sally uses a board to create waves. Sally investigates the effect these waves have on Susan who is floating on another board near the middle of the pool. Sally notices that the waves travel with a speed 6.2 m/s. a) If Sally moves the...
  27. W

    De broglie wavelength for helium and distance between atoms

    Homework Statement Consider a balloon filled with helium gas at room temperature (T = 294 K) and atmospheric pressure. Calculate (a) the average de Broglie wavelength of the helium atoms and (b) the average distance between atoms under these conditions. The average kinetic energy of an atom is...
  28. Summer95

    Ground state wavelength and uncertainty Bohr/deBroglie model

    A check my work question... Homework Statement Louis de Broglie tried to explain Bohr’s hydrogen atom electron orbits as being circles of just the right circumference such that an electron of the Bohr energy going around the circle will interfere constructively with itself. This seems to...
  29. atyy

    Why does wavelength affect diffraction?

    This question came up in the biology section https://www.physicsforums.com/threads/explain-different-types-of-light-microscopy.833990/. Q1: The longer the wavelength of a wave, the more easily it bend around an obstacle. I do understand the mathematics, but is there any intuition for it? Q2A...
  30. Safinaz

    Calculating the De Broglie Wavelength of an Accelerated Particle

    Homework Statement A particle of mass m and charge q is accelerated across a potential dierence V to a non-relativistic velocity. What is the de Broglie wavelength of this particle? Homework Equations Is it The Attempt at a Solution I think it's ## \frac{h}{\sqrt{2mqV}} ##, because ##...
  31. isnainidiah

    Why we use wavelength to divided into ray, wave and particle

    I want to ask something about light, light can be defined as ray, wave, or particle. The group formed because of the wavelength, if the wavelength is less than the dimension of equipment it is grouped into ray, if the wavelength is equal to the dimension of equipment it is grouped into wave, and...
  32. DaniV

    Gluon Wavelength in Nucleons & Barions

    The Gluones qualities are similler to the photones by the fact that both of them have a state mass of zero and dual wave-particle behavior.. My question is what the range of the wavelengthes of the Gluons in the nucleons and in another barions?
  33. jlefevre76

    Simulating Heavy Nuclei Reactions with Software: A Beginner's Guide

    Hey, is there software out there capable of simulating heavy nuclei? For instance, U235 or other fissile materials? When I say simulating, I mean using all the appropriate equations (nuclear strong force fields represented, Schrodinger equations represented, etc). Mainly, I would want one that...
  34. B

    What affects the intensity of different coloured lights?

    Okay, so I have completed a practical where I used a light box and then placed different coloured plastics in front of the light and measured the light intensity of each colour. From the results I found that yellow, orange and violet had the highest intensities, with red and green having the...
  35. A

    Understanding the Wavelength of Light: Explained Simply | 750 nm Explanation

    Hi 1)Is this sentence right? When we say for example the wavelength of red light in vacuum is 750 nm it means that the length of electric field and magnetic field that are perpendicular in the propagation direction of wave is 750 nm in one cycle? 2) We say that oscillating charges in antenna...
  36. D

    Wavelength of traveling wave on string (one end clamped and one end free)

    1. Homework Statement A 30-cm long string, with one end clamped and the other free to move transversely, is vibrating in its second harmonic. The wavelength of the constituent traveling waves is A -- 10 cm B -- 40 cm C -- 120 cm D -- 30 cm E -- 60 cm Homework Equations for second...
  37. F

    Heisenberg Uncertainty in wavelength and position

    Homework Statement Show that ## \Delta\lambda\Delta\ x>lamdba^2/4*pi## The Attempt at a Solution When I substitute de Broglie's p=h/lambda I get the equation of ##\frac {\Delta\x}{\Delta\lambda} > 1/(4*pi )##
  38. KaseyKC

    Relationship between wavelength and frequency in a medium

    Homework Statement Write down the relationship between the linear frequency and the wavelength of a light wave when the wave is propagating in a medium of refractive index, n.[/B]Homework Equations wavelength x linear frequency = speed of light speed of light = refractive index x speed of...
  39. M

    Thickness of a film given wavelength and phaseshift....

    A wavelength of incident light on a thin film is given, and also is known how much the rays coming out from the top surfaces are out of phase. How can be the thickness of the film calculate?
  40. F

    Show change in de Broglie wavelength from change in speed

    Homework Statement Show that for a nonrelativistic particle, a small change in speed leads to a change in de Broglie wavelength given from The Attempt at a Solution I have tried to expand the left hand side of the equation, but found that it gave the answer of v0/delta v. My definition of...
  41. Molar

    De Broglie wavelength of an atom

    In my book it is says, DeBroglie wavelength of a particle at temp T is, λ = h/√(2mKT) and DeBroglie wavelength of He atom is, λ = h/√(3mKT) Well, λ = h/ mv and mv2/2 = (3/2) KT and so , λ = h/√(3mKT) How to prove the first one..?? and why they are different...??
  42. H

    B Why is the uncertainty in position equal to the wavelength?

    Why is the uncertainty in position of an object which is determined by a wave equal to the wavelength of the object? I don't get it. Isn't the wave diffracted at the surface of the object? we can then calculated the distance from velocity and time accurately, can't we? is it because we must...
  43. B

    Why can't diffraction happen if wavelength>slit size

    I get that diffraction takes place when wavelength is smaller than slit size due to interference. I am confused though, if every point on the slit is taken as a new source when a wave passes through a slit, then surely, if the wave had a longer wavelength than the slit, then the let's say...
  44. 1

    What is saturation in terms of wavelength?

    could it be possible, to make a, for example, and lens that has a special texture, or colour and putting it on would make the pictures more saturated? or maybe make a pair of glasses for people who can't produce as much cones as others? my questions is because i can't really think of it, but...
  45. S

    Classical physics wavelength of monochromatic light

    Homework Statement A stopping potential of 0.50 V is required when a phototube is illuminated with monochromatic light of wavelength 600 nm. Monochromatic light of a different wavelength is now shone on the tube, and the stopping potential is measured to be 1.1V. What is the wavelength of this...
  46. S

    How Can the Speed of Sound Help Determine Room Temperature?

    Homework Statement Calculate the room temperature by using the speed of sound formula and using the given values. Known Data: Frequency = 480 Hz 2nd Resonant length = 54cm or 0.54m Homework Equations v = 331 + (0.60)T T = (v - 331)/0.60 v = fλ (Open-Closed air column) L = (3/4)λ The...
  47. D

    Problems with De Broglie's Wavelength

    I always used the matter-wave as an explanation for why the electron does not crash into the nucleus. As a standing wave, how could it? The wave would have to increase in frequency, almost infinitely, until it was the size of a point, the nucleus, which seemed like an impossible task. However...
  48. GM Jackson

    How does a black body emit as much energy as it absorbs?

    Homework Statement A black body absorbs all incident electromagnetic radiation, including visible light which has wavelengths from 380nm to 750nm. IR radiation has wavelengths that are so long they are measured in microns. That suggests that visible light has a higher frequency than IR, and...
  49. V

    Wavelength of Photons: 3-2 Transition

    Homework Statement Between which energy levels are the photons in this line transitioning? Wavelength= 660 * 10^-9 m Change in energy = 3.01 * 10^-9 A. 4 and 2 B. 3 and 2 C. 3 and 1 D. 2 and 1 Homework Equations...
  50. D

    Equation used to find kinetic energy of proton

    I am having trouble deciding when to use which equation. If you're given the wavelength of a proton, let's say 100 fm, and have to find the kinetic energy of it, how would you do this? Here are my ideas: Idea 1: Use lambda = h/p, where p = sqrt(2Em). Idea 2: Use E=(pc)^2+(mc^2)^2 =...
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