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. J

    Solving the Mystery of Wavelength Refraction: A Thin 200nm Film of Oil

    Homework Statement http://lon-capa.bd.psu.edu/res/psuerie/gwb6/physics/optics/e1p4.png A thin 200nm film of oil (n = 2.0) floats on water (n = 1.33). To a normal human, what wavelength will the film appear when viewed from above (nearly perpendicular to the film)? Homework Equations for...
  2. CAH

    Diffraction grating and wavelength

    Hi I've attached the question and mark scheme, I don't understand part 6(d)... Why have they used sin90? nλ=dsinθ If there is another order beam how can it be known the angel at which it exists from the zero order? Thanks
  3. J

    Calculate Wavelength of 6th Line in Balmer Series

    Homework Statement Compute to three significant figures the wavelength of the sixth line in the hydrogen Balmer series. Homework Equations 1 / lambda = R * ( 1/ n_final^2 - 1 / n_initial^2 ) R = Rydberg constant = 10973731.57 m^-1 lambda = wavelength The Attempt at a Solution I set up the...
  4. Amal George M

    Wavelength of matter wave at v=0

    if velocity of a huge particle is made zero what will happen?? will the particle spread out into the universe aka complete delocalization??
  5. A

    Calculate the wavelength of electrons traveling at 1.15x10^5

    Homework Statement Calculate the wavelength of electrons traveling at 1.15x10^5 m/s Homework Equations λ = h/m*v Given values: h=6.626x10^-34 J*s m=9.11x10^-31kg v=1.15x10^5 m/s The Attempt at a Solution I converted J*s to SI units (kg⋅m2⋅s−2) and then substituted out all known values, to...
  6. M

    Wavelength of light in relation to speed

    Hi guys, first ever post. My question is if light travels at the same speed regardless of its wavelength, doesn't this statement seem to contradict itself? If the light simply traveled in a straight line then sure, but different wavelengths i would think mean that a greater distance would...
  7. D

    How do I calculate wavelength?

    I've just begun learning physics for the first time. Please can anyone help me understand how to work through this problem? In an AC (Alternating Current) circuit, the current, I, measured in Amps (A) varies sinusoidally http://i1088.photobucket.com/albums/i332...How can I calculate the...
  8. K

    De Broglie wavelength of nitrogen molecules

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  9. J

    Radio waves received at distance <1 wavelength

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  10. T

    Building a half wavelength dipole antenna

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  11. A

    Finding the wavelength on a sinusoidal wave on a string

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  12. D

    Plotting energy as a function of wavelength

    Homework Statement Given work function W=2eV Plot energy of an electron knocked off with respect to wavelength Homework Equations E=hv-W The Attempt at a Solution E=h (c/(lambda))-2 I plotted this and I get a function that goes to infinity with zero wavelength and crosses the x-axis at 6000...
  13. K

    Dependence of Phase Velocity on Wavelength

    Homework Statement This is Problem 7.6 from Electronic Properties of Engineering Materials by Livingston. "Over a wide range of frequencies, the dielectric constant of a polymer is found to be proportional to the inverse square root of frequency. (a) How does the phase velocity of EM-waves...
  14. H

    Finding propagation speed/wavelength from an equation

    Homework Statement A wave is described by y=12sin(4t-8x). What is its propagation speed? A. 0.2 B. 0.5 C. 4 D. 8 E. 12 Homework Equations v=wavelength/period v=wavelength×frequency The Attempt at a Solution period= 2π/w=2π/8=.7853 But confused on how to find the wavelength?
  15. H

    How to find wave oscillations?

    Homework Statement A wave has a wavelength of 3.0m; a frequency of 25.0 Hz; and amplitude of 14.0 cm. The wave travels in the positive x-direction and has a value of zero at t=x=0. How many complete oscillations has the wave made at t= 20.0 s and x=4.2 m? A) 3132 B) 1566 C) 498 D) 25 E) 3...
  16. GiantSheeps

    Wavelength given time, velocity, and cycles

    Homework Statement As your hand moves back and forth to generate longitudinal pulses in a spiral spring, your hand completes 2.88 back-and-forth cycles every 6.98 s. The velocity of the pulse in the spring is 0.581 cm/s. What is the wavelength? Answer in units of m. Homework Equations v=λf...
  17. S

    Find maximum wavelength using minimum wavelength and frequency difference

    Homework Statement A radar receiver can be tuned to detect signals are different wavelengths. If the frequency difference between the minimum and maximum wavelength is 10 GHz and the minimum detected wavelength is 4910µm. What would be the maximum wavelength? Homework Equations λƒ=c The...
  18. X

    Wavelength in the visible spectrum most strongly transmitted

    Homework Statement A camera lens (n = 1.29) is coated with a thin film of magnesium fluoride (n = 1.71) of thickness 87.0 nm. What wavelength in the visible spectrum is most strongly transmitted through the film? Homework Equations λ = 2nt/m The Attempt at a Solution λ = 2(1.71)(87E-9m)/(1)...
  19. julianwitkowski

    Single Slit / Wavelength / Central Maximum

    Homework Statement A laser emitting light with a wavelength of 560 nm is directed at a single slit, producing an interference pattern on a screen that is 3.0 m away. The central maximum is 5.0 cm wide. Determine the width of the slit. I have two ideas of the answer but I'm not sure which is...
  20. K

    Getting Planck's Law in terms of frequency from wavelength

    Show that Planck's law expressed in terms of the frequency f is: u(f) = (8πf2/c3)(hf/(ehf/kT - 1)) from the equation: u(λ) = (8πhcλ-5)/(ehc/λkT - 1) When I do this algebraically by simply plugging in λ = c/f, I get: u(f) = (8πhc-4)/(f-5(ehf/kT - 1) which clearly doesn't involve the correct...
  21. A

    Finding wavelength from counting crest

    Homework Statement [/B] A stone tossed into a body of water creates a disturbance at the point of impact that lasts for Dt = 4.0s. Measurements indicates that the wave speed is v = 25 cm/s. (a) Over what distance on the surface of water does the wave group extend? (b) An observer counts 12 wave...
  22. K

    Atomic Data Convolution: Wavelength vs Intensity

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  23. S

    How Do You Calculate Wavelength and Wave Speed?

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  24. Spock

    What are the Wavelengths and Amplitude of these particles?

    What would the Wavelength of these particles be? Also if you could, what would the amplitude be, I'm guessing 0.
  25. M

    Please help my son year 12 physics -- frequency and wavelength

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  26. synMehdi

    Speed of EM wave depending on the frequency

    I know that in a vacuum, speed of light is constant. My question is more about the speed of light in a material like air. Dispersion of light in a prism tells us that the speed of light or the material index depends on the wavelength ( or frequency which is constant ) so I thought that air...
  27. D

    Calculate Wavelength Three Different Ways

    Homework Statement The angle to eighth maximum is 1.12. θ_m=1.12 The distance from the slits to the screen is 3.02m. L=3.02m The distance between the slits is 0.00025m. d=0.00025m The distance from the first minimum to the fifth minimum is 0.095cm. 0.0295/4=Δx=0.007375m λ=? Homework Equations...
  28. Davephaelon

    DeBroglie wavelength of Proton in H atom

    How would one calculate the de Broglie wavelength of the proton in the hydrogen atom as the electron and proton pirouette around their common center of mass, for the lowest orbital? I believe the center-of-mass of the system would actually be inside the proton due to the great differential in...
  29. D

    De Broglie wavelength of an ant

    An ant of mass m = 1.80×10−6 kg goes through a hole of diameter D = 5.00 mm in a window screen which has thickness L = 0.600 mm. (a) What should be the approximate wavelength and speed of the ant for it to show wave behavior as it goes through the hole? I am not sure what should the...
  30. A

    Calculating energy from de Broglie wavelength

    Given the relationships: \lambda = \frac{h}{p} = \frac{h}{mv} and E = hf for wavelike non-relativistic matter, and v = \lambda f for a general wave, one can obtain the result: E = \frac{h^2}{m \lambda^2}. Whilst for particulate matter, we have E = \frac{1}{2}mv^2, which when combined with the...
  31. A

    Understanding EM Spectrum: Emitting vs. Reflecting | IR Camera Examples

    Hello, I was wondering how one would be able to tell the difference between an object emitting a certain wavelength of the EM spectrum, vs. an object reflecting that same wavelength of the EM spectrum. For example: 1) Suppose I have an IR source at 7 microns. I point this source at water, and...
  32. predaylight

    De Broglie wavelength and ideal gas entropy derivation

    When the ideal gas entropy is derived, we consider N atoms in a box of volume=Lx*Ly*Lz. Then, we make the assumption that Lx,Ly,Lz >>de Broglie wavelength of atoms. I am not sure why we need to make this assumption? Thanks!
  33. R

    Wavelength, period of vibration in seconds

    < Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown > Okay, I am having trouble with the units. I have the values for the wavenumber and I am trying to find the period. These are the formulas that I am trying. T = 1/f ; f = c/lambda example...
  34. O

    Is it possible to create a specific wavelength

    I am wondering if a particular wavelength could be generated by Focusing two different wavelength lasers at the same spot? My hypothesis is no, because interference only affects amplitude and not wavelength,correct? Could there be another way of generating a specific wavelength from two...
  35. R

    Refractive Index change with Wavelength & Carrier Concentration

    I need to calculate the refractive index of a semiconductor material over a wavelength range (1×10-5m - 1×10-9m) and with different values of electron and hole carrier concentrations (i.e. n/p doped). I found this equation that relates those parameters: n+ik = √ [ (εm -...
  36. Avatrin

    De Broglie Wavelength at Relativistic velocity

    Homework Statement A particle has charge e and masse m0. It is accelerated by a charge V to a relativistic velocity. Show that its de Broglie wavelength is: \lambda = \frac{h}{\sqrt{2m_0eV}} (1+\frac{eV}{2m_0c^2})^{-\frac{1}{2}} Homework Equations \lambda = \frac{h}{p} Conservation of...
  37. K

    Diffraction wavelength of particles in moving frames?

    Here's a question I cannot seem to comply with my understanding of Quantum Mechanics. The characteristic wavelength of a particle is responsible for diffraction interference fringes, which is part of the wavefunction solution to the schrodinger equation. But the wavelength of a particle is...
  38. psuedoben

    Astronomy: Measuring Radio Wave Distance from Universe

    when astronomers receive bursts of high energy radio waves from distant parts of the universe, how are they able to tell how far they have traveled? does it have to do with the wavelength?
  39. B

    Wave function with a certain wavelength

    I have a number of questions about the wave function - 1. Do photons have wave functions like the one in Schrodinger equation? 2. If they do, when you send out a wave function with a certain wavelength, then because you know the momentum with no uncertainty the uncertainty of the position...
  40. E

    Measuring Wavelength Homework: Middle of Lines or Book?

    Homework Statement Im not sure how to measure the wavelength when given this picture. Homework Equations The picture looks like this, it has two slits. The Attempt at a Solution My book says that the wavelength is 1 cm. When I measure from the middle of a white line to the middle of the...
  41. H

    Units of plancks law in terms of wavelength

    The dimensional term in Planck's law (after getting rid of steradians) is [itex]\frac{h c^2}{\lambda^5}[\itex]Which seems to yield units of J*m/s. However, Wikipedia suggests that the units are J/(m3*s). If wikipedia is right, how do you get that answer?
  42. Q

    Calculating Wavelength in a Ripple Tank: Understanding the PS1-PS2 Equation

    Homework Statement Two sources 6.0 cm apart, operating in phase, produce water waves. A student selects a point on the first nodal line and measures from it 30.0cm to a point midway between the sources and 5.0cm (on the perpendicular) to the right bisector. a) what is the wavelength Homework...
  43. F

    Calculate the wavelength of the n= 4 -> 3 transition in He

    Homework Statement Calculate the wavelength of the n = 4 → 3 transition in 4He+ to an accuracy of 4 significant figures. (R∞=109 737 cm-1.) (Fine structure effects can be neglected.) Homework Equations \frac{1}{λ} = \frac{m}{m_e} R_∞ (\frac{1}{n_1^2} - \frac{1}{n_2^2}) where λ is wavelength...
  44. P

    Sound waves in a closed pipe Problem

    Homework Statement Before I write the question you should know that my maths is all correct in my solution but I must have used the formulas incorrectly (or used the wrong formulas). I can't pinpoint where I've gone wrong or if I have left a formula out (I'm a teacher solving this question for...
  45. H

    Quarter wavelength confusion

    Reading up on quarter wave transmission lines and I'm confused about the actual length of the line. Is a quarter wavelength line equal to the length of the incident and reflected wave? Or is it only equal to the length of the incident wave?
  46. Lamdbaenergy

    Planck's law (wavelength, frequency, angle?)

    So I was just looking around today and stumbled upon something called Planck's law. I saw an equation and quite few more of them that looked like this, I'm familiar with all of the other variables and constants already, but don't get the E (hv/kT) part, yet. Is E the energy of the photons you...
  47. N

    Diffraction Grating wavelength

    Homework Statement A beam of light comprises two wavelengths is passed through a transmission diffraction grating. When viewed at an angle of 21.1° to the incident direction, the second order maximum for one wavelength is overlapped with the third order maximum for the other wavelength. The...
  48. A

    Doppler effect - Apparent change in frequency or wavelength?

    Hello, I've been thinking about what exactly is the doppler effect and I'm not sure I understand it because I thought it meant a change in frequency due to relative motion while at the same time its defined in terms of changing wavelength such as in red shift or blue shift. Case 1 The...
  49. C

    Plastic or glass that can block one colour/ wavelength?

    Hi, new member here, I know very little about physics so have no idea if this is a very basic question or not, but I was wondering if anyone knows the answer to the following: Does there exist a type of plastic or glass that (whilst remaining completely see through) can allow the user to see...
  50. D

    How Does Changing Wavelength Affect the Central Peak in Single-Slit Diffraction?

    In my physics book, one of the basic quick quizzes checkpoints asks what happens to the central peak in a diffraction envelope when you decrease the wavelength of light (from 650 nm to 450 nm, for reference). My understanding is that the width of the peak would decrease, while the number of...
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