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. X

    How do we measure the wavelength of electromagnetic waves?

    How the wavelength of wave is measured? My idea of electromagnetic wave is there is an invisible line traveling through space moving up and down like a sine wave we see on CRO. Is this idea correct? Or is it the the variation in electric and magnetic field of the wave that we relate this...
  2. B

    Modern Physics I: Find Energy Loss & Wavelength

    Homework Statement An electron with energy 10^3 MeV collides with a photon whose wavelength corresponds to the maximum wavelength of the 2.7-K cosmic background radiation. What is the maximum energy loss the electron can suffer as a result of the collision? What is the wavelength of the photon...
  3. Shackleford

    Compare transition wavelength

    6. http://i111.photobucket.com/albums/n149/camarolt4z28/2010-09-23195548.jpg?t=1285299756 I'm thinking I use the omegaij formula to determine the frequency between energy levels and then use that to calculate the wavelength...
  4. F

    Wavelength, emission spectrum, electron transitions

    Homework Statement Determine the wavelength (in nm, to one decimal place) of the line in the emission spectrum of the He+ ion produced by a transition from n = 3 to n = 1. Homework Equations I used the Rydberg equation for this, although I'm not sure it is the correct one to use...
  5. A

    De Broglie wavelength problem

    Homework Statement By estimating the De Broglie wavelength and the inter-particle spacing, find whether the following systems of particles are degenerate: (i) a gas of neutrons in a neutron star with mass density 10^17 kg/m^3 at the temperature of 10^8K (ii)a gas of oxygen molecules at...
  6. jinksys

    Calculating De Broglie Wavelength from Kinetic Energy

    Homework Statement Show that the de Broglie wavelength of a particle of mass m and kinetic energy KE is given by \lambda = \frac{hc}{\sqrt{KE(KE + 2mc^2)}} Homework Equations The Attempt at a Solution I know: KE = {\gamma}mc^2 - mc^2 = pc - mc^2 But from here I am...
  7. P

    Energy vs wavelength for a photon in GR

    If a theoretical single photon followed a geodesic toward a large mass in space, I understand that the wavelength would shorten as it approached the mass. How would the energy be conserved within the photon, because the frequency must surely remain the same?
  8. E

    Why is wave diffraction around object better at longer wavelength?

    Wikipedia: Does the wave theory itself (the mathematical formulation) imply that diffraction is more efficient at longer wavelengths? I just want the logical connection of why (for example) radio waves diffract and bend around objects better than visible light. :confused: Thank you.
  9. fluidistic

    Find the wavelength of the particle

    Homework Statement I'm not even sure the problem is about matterwave: A particle of mass m and charge e is accelerated by a potential difference V. Find the wavelength of the particle. Show that this result agrees with the classical one when the non relativistic limit is taken.Homework...
  10. fluidistic

    What is the minimum wavelength of x-rays produced by a 50 kV emf?

    Homework Statement An x-rays tube is connected to a 50 kV emf. Calculate the minimum wavelength that one can find in the radiation spectra that the tube produces.Homework Equations No idea! This is why I ask help here. The Attempt at a Solution Stuck at start. I've searched in google and...
  11. 2

    The Atom: wavelength, energy, kinetic energy, etc. of photons

    here are the problems that I need help with: http://imgur.com/a/fERMC/1 I am afraid that I know not much information about the questions. Sadly, I am enrolled in a poorly written Physics class online. I am not looking for the answers, but just how to go about finding them. The book never...
  12. D

    Gradient of Wavelength vs Period Graph?

    We've got a table of periods (in seconds) and their corresponding wavelengths for creating resonance in a closed pipe. I've been told that plotting a graph of period (on x axis) vs wavelength, and finding the gradient of that linear line will tell me the speed of sound in air. I can do that...
  13. D

    Calculating Time & Wavelength of 1000Hz Noise

    Hi, "Somebody makes a noise with a frequency of 1000Hz. Calculate how long it will take to reach somebody 3m away. What will be the wavelength?" I can't figure out how it fits into any of the formulas I have! Thanks! :)
  14. atomqwerty

    Calculating Theta for Lowest Wavelength Electron Beam

    Homework Statement An electron beam (energy 119,9 eV) contacts perpendicularly on a Ni plate, with interatomic spacing d= 0,215 nm. At which angle Theta will be obtained an electron beam with the lower wavelenght possible? Homework Equations n\lambda=d sin(\theta) (Bragg's for...
  15. S

    Deriving the De Broglie Wavelength

    E=mc^2 and E=hf. In Special Relativity, how can y=h/p be derived from E=hf?
  16. T

    Is There a Maximum Wavelength for Electromagnetic Radiation?

    Is there any lower limit on the frequency of electromagnetic radiation? I imagine that beyond a certain frequency it becomes impossible to detect, but is there anything in the maxwell equations that establishes a maximum wavelength (besides the limits of the size of the universe)? Thanks
  17. M

    De Broglie wavelength application: molecular vibrations?

    Homework Statement In his presentation of the de Broglie wavelength and the wave/particle duality, my quantum prof. has an exercise: "Find the de Broglie wavelength of a molecular vibration. Do quantum or classical laws apply?" Homework Equations wavelength = h/(momentum) ...
  18. S

    Find speed of quasar from observed and actual wavelength readings

    1. Astronomers on Earth observe a feature at 442 nm in the spectrum of a distant quasar. However, it is known that this feature corresponds to 581 nm in the rest frame of the quasar. Calculate the speed of the quasar. Enter your answer as a fraction of the speed of light, positive if the quasar...
  19. J

    Average wavelength for blackbody radiation

    The maximum wavelength for blackboby radiation is .29/Temperature. Is the average wavelenght 1.84 times the maximum for all temperatures?
  20. G

    What is the longest wavelength ever seen by the human eye?

    I've gotten curious about how the human eye's sensitivity to long wavelengths drops off. What's the longest wavelength anybody has ever seen? I know there is nonzero (but very low) sensitivity to 800+ nm light, but does anybody know the extreme long wavelength limit of human vision?
  21. A

    Energy and Wavelength of a photon in pair production

    Homework Statement Electron and positron each have a kinetic energy of 220 keV even when far apart. Homework Equations The Attempt at a Solution I have no idea. My book says the answer 1.46 MeV, 8.49 x 10^-13 m but I don't know how to get that.
  22. M

    Relation between mass and wavelength

    Hi, Why are mass and wavelength are inversely proportional?
  23. A

    Colour (RGB/HSV/HSL) to wavelength.

    I've been searching on this topic for the past 10 minutes and then realized it'll be better just asking someone about it. Anyway yeah, the question is, are there any specific equations that will give me the wavelength when I give it the colour values? I saw some sites where each colour in the...
  24. T

    Observation, wavelength and resolution

    Why are short wavelengths (of e.m. radiation say) required for observing the location of a small particle? Classically, I could imagine sending a wave train of light (or a photon) of different frequencies onto an atom in free space. Providing the electrons in the energy levels of the atom can...
  25. D

    De Broglie wavelength and it's dependence of the frame of reference

    Hello, I've always wondered about the "relativity" of the De Broglie wavelength. The wavelength depends on the momentum of the specific thing we are observing, thus on different frames of reference(F.O.R from now on :P) we might get different answers. I have been looking through the web to...
  26. W

    De Broglie's Wavelength (matter wave)

    Homework Statement Parallel beam of "cold" neutrons in the x-axis, with energy 0.1eV strikes a slit system in y-z plane. Slits are parallel to the y-axis 1 micron apart. What will be the distance between the detector at x=20m which records the highest flux of neutrons, and the closest one...
  27. U

    How Do You Determine Quantum Numbers from Hydrogen Atom Wavelengths?

    Homework Statement Two of the wavelengths emitted by a hydrogen atom are 9.50×10-8 m and 4.65×10-6 m. What are the m and n values for the first wavelength? Homework Equations E = -13.6eV/n2 E = -13.6eV/(m2 - n2) restriction:m > n E = hf f = c/λ 1 eV = 1.6 x 10-19J The Attempt at...
  28. C

    What is the process for deriving a galaxy's (i.e. Milky Way) wavelength?

    I am creating this wavelength chart (attached). I was told to use Compton's formula; I got this: (6.626068 × (10^(-34))) / (1.1542e+42 * 299 792 458) = 1.91493535 × 10-84 Apparently, it is substantially off scale. I was then told to try de Broglie wave. Wikipedia only shows relations...
  29. R

    Exploring the Planck Wavelength: The Smallest Possible Measurement

    It there a smallest possible wavelength? And if there is, what is that wavelength?
  30. S

    FM vs AM: Which Radio Wavelength Is Bigger?

    it has been a while. i need to know which wavelength is bigger FM radio or Am radio?
  31. J

    Calculating the de Broglie Wavelength

    Homework Statement Calculate the de Broglie wavelength of an oxygen molecule (molecular mass 32)in air at room temperture. Homework Equations P = h/ \lambda P= mv E= hv = 1/2mv^{2} = P^{2}/(2m)The Attempt at a Solution hv = 1/2mv^{2} h = 1/2mv If v = P/m then h = mp/2m so p= 2h This...
  32. A

    Meaning of frequency and wavelength of photon

    can anyone tell me the meaning of frequency and wavelength of photon.what exactly it indicates?As it is particle then how it can have frequency and wavelength?frequecy is charaterstics of wave.
  33. AJ Bentley

    Wavelength dependence of a resonant coil?

    This question relates to the design of a Tesla coil, which is basically a loose-coupled, tuned transformer. The secondary is a series LCR circuit that develops a high voltage across a capacitor. The capacitor takes the form of a toroidal 'top-load' to ground. In the literature, much...
  34. TrickyDicky

    Can Electromagnetic Wavelength Replace Geometrical Length as a Distance Measure?

    Could electromagnetic wavelength be used as a legitimate distance pattern? I mean is it OK to exchange geometrical length with physical wavelength? For example, given a bundle of light rays following geodesics in empty space, can the length between a given pair of geodesics be equivalent to a...
  35. A

    How Does Wavelength Affect Data Transmission Capacity?

    What kind of electromagnetic radiation can carry more information?. I mean, what is the relation between shorter or longer wavelength and the information that can go within. I wonder how the dynamics of this process works, considering that sound waves also can carry information, as well every...
  36. C

    Importance of de Broglie wavelength of matter

    I can work out the wavelengths fine, but I am unsure of the answer to the second part, any help would be much appreciated
  37. R

    How Does Wavelength Affect Light Penetration in Photodetectors?

    Homework Statement what is the physical significance of wavelength (not the definition)? Homework Equations suppose, in photodetectors (like avalanche or p-i-n photo diodes) incident light having more wavelength, penetrates more in the diode (particularly in depletion region : )...
  38. A

    Frequency & Wavelength of Radar & Sonar: Get Answers Here!

    Can anyone tell me what frequency and Wavelength Radar and Sonar work in. I think Radar have a frequency of 300giga hertz (UHF), wavelength 0.1 Sonar is somewhere between wavelength 100k - 10k metres, frequency 3k - 30k hertz. Please help me thanks,
  39. P

    Finding Electron Speed and Wavelength

    Homework Statement The wavelength of an electron is 4.4 × 10−7 m. How fast is it moving? The Planck’s con- stant is 6.62607 × 10−34 J · s . Answer in units of m/s. 013 (part 2 of 2) 10.0 points If the electron has a speed of 9 × 106 m/s, what is its wavelength? Answer in units of m...
  40. J

    Relativity - wavelength differences for two observers?

    hi, my exam is tomorrow and I really need to understand this. Imagine a region of constant gravitational field, directed "downwards". There is a photon traveling in this downward direction. There are two observers, A and B. At t=0, they do not have any relative velocity. However, B is fixed...
  41. K

    Long Wavelength Radio Astronomy

    Just curious, what is the longest wavelength we can currently observe with our instruments, & are there are good sources for future (even if just theoretical) projects at longer wavelengths (future projects do no have to be based on Earth)?
  42. M

    Max wavelength of CMB radiation

    I'm doing OCR A-Level Physics, and in my textbook it states "They (Penzias and Wilson) made a calculation to find the temperature of the source of the radio waves, which had a maximum intensity at wavelength 1.1 cm, and found it to be 2.7K". This was all good and well, until I answered a...
  43. matt_crouch

    Doppler effect wavelength from car

    Homework Statement A car is traveling at 30m/s in still air. the frequency of the siren on the car is 600hz. The velocity of sound in still air is 330 m/s. what is the wavelength of the sound waves a)directly in front of the car b)directly behind the car What is the frequency of the...
  44. K

    Finding wavelength of hydrogen atom when changing energy states

    Homework Statement Find the wavelength of the radiation emitted when a hydrogen atom makes a transition from the n = 6 to the n = 3 state. Give answer in µm. Homework Equations z^2 / n^2 x 13.6ev delta E = E2 - E1 = hv The Attempt at a...
  45. Math Jeans

    Wavelength limits of Planck's Law

    As is well known, Planck's radiation law for the distribution function of blackbody radiation used a then new concept of energy quanta in order to describe experimental data. The distribution functions formulated by Wilhelm Wien and Lord Rayleigh, describing the same phenomena, were...
  46. K

    What is the threshold wavelength for this surface?

    Homework Statement A surface of a substance has a work function of 2.24 eV. (a) What is the maximum kinetic energy of ejected electrons if the incident radiation is of wavelength 419 nm? eV (b) What is the threshold wavelength for this surface? nm Homework Equations E=hf...
  47. M

    Calculating Wavelength and Speed of a Standing Wave on a String

    Hey guys and girls, I'm having a hard time trying to start this problem. I think I have an idea of what to do to start it, but I'd like someone to verify it for me: Homework Statement A mass, m = 5.50kg hangs from a cord around a light pulley. The distance between point P and the pulley...
  48. B

    Real component of the wavelength of microwaves in copper

    I am trying to work out the real component of the wavelength of microwaves in copper. I am given n2=er=-i sigma/eo omega where n is the refactive index er is the relative permitivity eo is the permitivity of free space i = sqrt(-1) omega is the frequency of the microwave sigma is the...
  49. F

    Calculating Slit Width Using Microwave Wavelength

    Homework Statement Microwaves of wavelength 2.80 cm fall on a slit and the central maximum at a distance of 1.0 m from the slit is found to have a half-width (i. e. distance from middle of central maximum to first minimum) of 0.67 m. Find the width of the slit.
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