What is Wavelenght: Definition and 42 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. V

    A Extracting Color from a Spectral Date

    Hello everybody, I would love some help on the following; I have a spectral date (As image 1 below) formed by the wavelength, refraction index and the absorption coefficient. Is there any way to relate this spectral date to a dominant wavelength? or in a few words extract the color from this...
  2. Mikkel

    I At what wavelength do we observe ionized gas?

    Hello! My question is this: At which wavelength do we observe ionized gas? My understanding is this: An ionized gas is basically a soup of particles flying around, because of the extreme temperatures (plasma?). So if we have particles moving around with such high velocities, I would expect to...
  3. Uchida

    Minimium diameter of an electromagnetic beam in terms of wavelength

    Is there a limit on the minimum diameter that a collimated electromagnetic beam must have (lasers or masers), in terms of its wavelength, or it is possible to create a beam with its diameter smaller than its wavelength? I'm considering a colimated planar wave directly from the source, and not...
  4. AncientOne99

    Wave equation, wavelenght not given

    Homework Statement Wave problem Given data : f = 20 Hz y0 = 0.005 m t = 0.1 s x = 0.4 m1. The end portions of stretched string oscillates in the transverse direction with a frequency of 20 Hz and an amplitude of 0.005 m. Wave , which travels along the string, made in 0.1 second, 0.4 m long...
  5. B

    B Radio Waves & Penetration: Why Can They Pass Through Walls?

    Why do radio waves pass through walls while visible light can't? I guess this has something to do wit the wavelength. What I know is that higher wavelength means higher ability of penetration. So why radio waves penetrate obstacles?
  6. B

    How do you work out the wavelegth (Franck-Hertz experiment)?

    Homework Statement In a Franck-Hertz experiment carried out with potassium vapour, it is found that the current falls off rapidly at an applied voltage of 1.62V. Calculate the wavelength of the expected spectral line in the emission spectrum of potassium when this voltage is reached. Homework...
  7. okandrea

    Wavelengths: Length between 2nd-order fringes

    Homework Statement Light of wavelenghs 4.80x10^2 nm and 632nm passes through two slits 0.52 mm apart. How far apart are the second-order fringes on a screen 1.6m away? λ₁ = 4.80x10^2 nm = 4.80x10^-7m λ₂ = 6.32x10^-7m d = 0.52mm = 5.2x10^-4m n = 2 L = 1.6 Homework Equations (Maxima/Bright)...
  8. shihab-kol

    What Is the Nature of Black in the Visible Spectrum VIBGYOR?

    In the visible spectrum VIBGYOR, there is no black colour.So, what do we percieve as 'black' ? Another of my queries is that when dispersion takes place there is a change in wavelength but not so in case of frequency. But they are related inversely. So, why does this happen?
  9. P

    Reflection dependence from wavelenght

    Homework Statement Hi guys, I have this exercise and I m confused. Incident (white light) light ray is perpendicular to glass surface , glass plate is 0,4microm thick. Which wavelengths in reflected ray becomes more intense? Homework EquationsThe Attempt at a Solution So i know that light is...
  10. 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?
  11. moenste

    Young's slit: find wavelenght, double slit separation

    Homework Statement 1. The distance between the 1st bright fringle and the 21st bright fringe in a Young's double slit arrangement was found to be 2.7 mm. The slit separation was 1 mm and the distance from the slits to the plane of the fringes was 25 cm. What was the wavelength of the light...
  12. 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?
  13. abm77

    Waves -- Find the lowest possible values for m_r and m_v

    Homework Statement Two slits are separated by a distance of 4.40x10-6m and illuminated with two monochromatic light sources with wave lengths of 600nm (red) and 400nm (violet). The mr bright fringe of the red light coincides with the mv bright fringe of the violet light. What are the lowest...
  14. O

    What is the Width of the Antenna for Optimizing TV Reception on Channel 10?

    Homework Statement The half wavelength "dipole" loop roof television antenna is most sensitive to electromagnetic waves with a wavelength twice the width of the antenna. The frequency of the waves for TV channel 10 is 200 MHz. If you want to optimize the TV reception for channel 10, how wide...
  15. K

    How to find wavelenght of a 3m spring with 2,5 Hz?

    Hi! I just can't figure this out. A 3m long spring makes transverse waves with a 2,5 Hz frequency. What is the wavelength? I don't even know where to start, because in out incredible small physics course, we never learned this. :)
  16. A

    Shortest wavelenght emmited by a black body

    what is the shortest and longest wavelenght that has experimentally observed for a black body? Additoinally what are the theoretical limits? I know it's a hard one,
  17. T

    Can FGR and the fine structure constant explain high intensity in dark field?

    Let's say I irradiate a sample that has an absorbance β with light of a wavelenght λ1. Is there a way to relate the initial λ1 and the diffracted/scattered λ2 using β?
  18. C

    Photon Wavelength of He+ Emission Spectrum

    Homework Statement An electron of wavelength 1.74 \times 10^{-10} m strikes an atom of ionized helium (He+). What is the wavelength (m) of the light corresponding to the line in the emission spectrum with the smallest energy transition? Homework Equations Kinetic Energy...
  19. A

    Is the de Broglie wavelenght incongruent with particle in a box calculation?

    Dear Physics Forum, I think I am confused in applying the correspondence principle in QM, using the particle in a box and de Broglie wavelength calculations for massive (macroscopic) objects. Why is the calculated energy of a massive object so small in the particle in a box E = h2/8mL2...
  20. N

    De Broglie wavelenght as a function of an accelerating potential

    Hello everybody at physicsforums.com! This is my very first topic in here, although I visit the forum for some time. I'm from Brazil and as english is not my mother language, i ask you not to be so harsh with my probables grammar mistakes XD. Well, so let's get to business. I have...
  21. M

    Wavelenght associated with electron

    [b]1.given mass of electron = 9.11*10^-31 ... kinetic energy=1mega electron volt [b]2. Homework Equations :: k.e=1/2mv^2 and λ=h/mv [b]3. The Attempt at a Solution :: am unable to get it...can anyone ry...
  22. V

    Wave Length of Photon: How Many Wavelengths Does It Contain?

    Hello all, The above quote is the first part of a reponse to a 2005 OP's question about frequency of a photon, and one of the few hints to an answer to one of my own enquiries about the wavelenght of a photon... I understand that EM waves come in a vast number of frequencies, however I was...
  23. S

    More wavelenght has an electromagnetic wave the minus frequency

    Hi, i read the more wavelenght has an electromagnetic wave the minus frequency it has, but how is possible to prove that? what experimenst were done? Thanks!
  24. N

    Electron falling between two orbits produces certain wavelenght of light

    Homework Statement Between which two orbits of the Bohr hydrogen atom must an electron fall to produce light of wavelength 954.8 nm ? Homework Equations E = hv E = R(1/n1^2 - 1/n2^2) The Attempt at a Solution I've got it down to the differences in the reciprocals of the squares...
  25. X

    Frequency & Wavelenght of EM wave

    Frequency & Wavelenght of EM wave! Hi..on some other thread i found this link showing animation of propagation EM wave: http://www.molphys.leidenuniv.nl/monos/smo/index.html?basics/light_anim.htm it has cleared my one doubt, because i used to think that EM wave is like an invisible line...
  26. D

    Wavelenght, index of refraction and speed

    THe wavelength of a red helium-neon laser light in air is 632.8 nm. A) what is the frequency? ( i already figured this out to be 4.7 x 10^16) B) what is its wavelenght in glass that has an index of refraction of 1.50?( i do not know where to or if i have to plug in the refraction into an...
  27. S

    Does the photon wavelenght come back to original when one path is blocked ?

    does the photon wavelenght come back to original when one path is "blocked"? Subject: Single particle (photon) interference in double slit or half silvered mirror experiment...question about wavelenght and phase shifts... in the half silvered mirror experiment or the double slit experiment...
  28. M

    Trasverse wave wavelenght and velocity problem

    Homework Statement Along a long tense rope are traveling transverse waves with amplitude A= 10 cm. What is the wavelength, if at any given time the distance between two consecutive neighboring waves y= 5 cm is d= 6 cm? With what velocity are the waves spreading, if the maximum transverse...
  29. O

    De Broglie wavelenght of Earth and Moon

    Hi, Could someone please crunch for me the de Broglie wavelenght (\lambda), frequency (f) and energy (E) of Earth at perihelion (30300m/s) and at aphelion (29300m/s) and mean (29800m/s) Here are the numbers and formulas: \lambda=h/p , f=E/h , p=m*v (momentum=mass*velocity) h - Planck's...
  30. I

    Derivation of Doppler Shift from Frequency to Wavelenght

    Homework Statement Derive the doppler shift equation from the equation in terms of frequency to one in terms of wavelenght. Clues: frequency=c/lamda, use Taylor's expansion, velocity of source is much smaller than velocity of wave. c-velocity of wave v-velocity of source f-frequency...
  31. A

    Electron and photon wavelenght

    an electron and a photon have the same energy. at what value of energy (in eV) will the wavelength of the photon be 10 times that of the electron? ( 10.3eV) how to get the answer? anybody help please
  32. W

    Wavelenght of the incident light

    Homework Statement An incident light shines on a mercury metal plate with a work function of -4.5 eV. The stopping voltage is observed to be -1.65 volts. What is the wavelenght of the incident light? Homework Equations wavelength=hc/E-0(it's a Greek sign n i don't have it in my...
  33. S

    Calculating Mean Thermal Wavelength for Relativistic Particles | Tutorial"

    hi i want to calculate "mean thermal wavelenght for relativistic particles"for example for photon . i don't khow how can i do it. please help me. thankyou.
  34. D

    De Broglie Wavelenght of a 5.5Mev

    Calculate the de Broglie wavelenght of a 5.5 Mev alpha particle emitted from Am (241) nucleus, could this particle exist with inside the Am (241) nucleus (diameter = 1.6x10^-14m)? the wavelenght: Lambda=h/p = (hc) / (sqrt[2mc^2)xeV) = 1240 / sqrt(2x3727.38x10^6x5.5x20^6) ?
  35. J

    Understanding the Effects of Wavelength and Frequency on IR and UV Heat Transfer

    hey how come the IR heat up materials more than UV ? and why people say IR go longer distances the way i see it : UV have faster frequencies, they should have more energy while IR have slower frequencies, should have less energy or is it that when hitting a electron , photons that...
  36. C

    Localization vs De Broglie wavelenght

    Localization vs De Broglie wavelength First of all, I would like to say hello to everybody since this is my first post, even if it's been some time since I read Physics Forums. Second, sorry for my bad English, I'm Italian :) Third, the issue: I read from my teacher's notes, that a...
  37. R

    What color will the oil appear and calculate the wavelenght

    An oil slick 122 nm thick (n = 1.4), lying on water, is illuminated by white ligiht incident, perpendicular to its surface. What color will the oil appear and calculate the wavelenght.
  38. S

    Simple: Finding the wavelenght

    I have a picture of a wave I am looking at. Each increment on the equilibrium line is 420 cm. I am asked to find the wavelength. there are 7 increments between one location of the first wave and the second wave. I multiply 7 times 4.2 meters and the answer is still wrong. Why?
  39. N

    RGB to wavelenght or viceversa.

    How would one convert RGB values to a wavelength value OR a wavelength value to RGB? ie 180,180,60=?
  40. M

    What wavelenght is expected for light composed of photons

    What wavelenght is expected for light composed of photons produced by an n= 3 to n=1 transition in a hydrogen atom? How do u work this out? Iam pretty confused.
  41. N

    What is the range of wavelengths for visible light?

    Wavelenght of Visible Light? is it 400nm to 800nm or is it 450nm to 750nm thanks nautica
  42. D

    What determines the colour? Frequency or wavelenght?

    What determines the colour? Frequency or wavelenght?