Wavelength Definition and 90 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. R

    Progressive wave, wavelength moving in the opposite direction

    I'm trying to find the wavelength. However, I don't understand why the wavelength is different if the wave is moving in the +z direction. I have ##\Psi(z=15cm,t) = \hat{x} 6 cos (\frac{\pi}{3}t)## ##\Psi(z=12cm,t + 2s) = \Psi(z=18cm,t)## For a wave moving on the -z direction I know that the...
  2. C

    Resultant Frequency and Wavelength of Interfering Sound Waves

    ##-w1## and ##-w2## are to shift the cosine graph to the right, and ##\frac{2pi}{\lambda}## is to stretch the graph. But I can't seem to draw an appropriate ##y1+y2## graph (quite irregular) and I struggle to find the resultant frequency and wavelength. Also, why is there angular frequency in a...
  3. S

    Wavelength in relation to the Dielectric Constant Dk

    Hi, On slide 9 of this presentation: http://www.globalcommhost.com/rogers/acs/techsupporthub/en/docs/MWJ_webinar_June20_2017_JC_microstrip_coplanar_stripline_final.pdf it states the signal wavelength can be changed with dielectric constant Dk. As far as I understand the wavelength and the...
  4. D

    Cauchy's law from Lorentz model

    Hello fellow physicists, I need to prove that when ##\omega << \omega_0##, Lorentz equation for refractive indexes: ##n^2(\omega) = 1 + \frac {\omega^2_p} {\omega^2_0 - \omega^2}## turns into Cauchy's empirical law: ##n(\lambda)=A+\frac B {\lambda^2}## I also need to express A and B as a...
  5. A

    I Plotting Solar spectrum

    I'm trying to plot the solar spectrum (Wavelength versus Flux) from a table of values I'm given. I'm given 3 columns; Solar Flux Arcturus Flux Wavelength Plotting Solar Flux versus Wavelength gives me a graph (below) that is very difficult to resolve. There are 21,000 data points as well. If...
  6. A

    I How do Limb-Darkening curves differ at two different wavelengths?

    Does the limb-darkening curve fall off faster at shorter wavelengths or at longer wavelengths?
  7. jdawg

    Total Emissivity as a Function of Temperature (Ceramics)

    Hello, I’m trying to better my understanding of how the total emissivity changes with temperature for ceramic materials. Currently it is my understanding that non-metals typically have a high emissivity. A sanded surface will result in a higher emissivity, and that spectral emissivity varies...
  8. I

    B Particles with small Wavelengths passing through huge slits?

    I´´m confused. How can a single photon in the lightspectrum with wavelength of a few hundert nanometers go through both slits in the double slit experiment at the same time. I understand the wave- particle duality and the concepts in principle. My confusion is in the context of little wavelength...
  9. P

    B Can it escape the event horizon if the wavelength is long enough?

    Can electromagnetic radiation escape from the event horizon of a Black Hole if the wavelength is long enough? What if a Black Hole contains electric charge, hypothetically supposing we dumped a large number of protons into it? Electric charge is mediated by the electromagnetic force. So the...
  10. P

    Sending a sound wave of 1cm wavelength through a 0.1Pascal medium

    I answered the first part of the question where I estimate the radius of ##O_{2}## is ##\approx 1.5 \times 10^{-10} \ \text{m}##: $$ p = \frac{KT}{l 4 \pi r^{2}} = \frac{(20+273.15)(1.38\times 10^{-23})}{(0.1)(4\pi)(1.5 \times 10^{-10})^{2}} = 0.143 \ \text{Pa}.$$ The confusion arises on the...
  11. F

    Why does the amount of Refraction depend on wavelength?

    I understand that electrons of a material have a natural frequency of vibration and the refractive index results from the phase difference between the incident light's field oscillations and the field oscillations of these electrons...
  12. S

    De Broglie Wavelength problem

    I tried using lamba = h/p as follows: (6.626 * 10^-34 J *s) / (8 m.s * 0.6 kg) = 1.38041667*10^−34 and then using the small angle approximation sin(alpha) = lamba/d as follows: (1.38041667*10^−34)/(0.6m) = 2.30069444 * 10^−34 then converting to radians with the following: (2.30069444 *...
  13. A

    Tension of a cello string

    wavelength of string= 2*L wavelength of string=2*0.70m= 1.4m velocity of string= frequency * wavelength velocity of string= 220Hz * 1.4m= 308 m/s tension= (308m/s)^2 * 0.00196 kg/m =186N Is the tension correct?
  14. frostysh

    B Help with understanding the Doppler effect

    My answer on this question for now is that producing a waves in the medium is an event which is basically must be invariant in the any of frame of references. For an example: a brick is freely falling, then the brick suddenly splinted into two pieces — no matter from which frame will we observe...
  15. J

    Doppler Effect Problem

    Pretending the siren is at rest in air: Wavelength = velocity/frequence --> (343 m/s) / 10,000 Hz = .0343m. I don't believe this is the correct way to go about solving the problem, since the vehicle is moving at the start and the siren is not at rest.
  16. T

    What is the difference between 1/2 wavelength and 2 overlapped wavelength? (pulsed laser autocorrelation)

    So, I was working on autocorrelation for my pulse laser system and I started to wonder what is the difference between single wave with 400nm of wavelength and two 800nm waves overlapped. In the knowledge, I know of, is that wavelength is the length between two picks. And when it is pulse laser...
  17. laurieke

    Wavelength of light in a dielectric material

    Homework Statement In a physics lab, light with a wavelength λ0 travels in vacuum from a laser to a photocell in a time t1. When a slab of glass with a thickness d is placed in the light beam, with the beam incident along the normal to the parallel faces of the slab, it takes the light a time...
  18. H

    Transition energy estimation based on bond length

    I come across this question in a text book. Somehow my result is way off from the solution answer. I used the energy formula for particle in a box with n(Initial) = 22 and n(End) = 23, the calculated box length is 732 pm. I arrived at an answer of 39.3 nm. The answer from the answer book is but...
  19. L

    Calculating the wavelength of a surface wave after impact

    Homework Statement There's a bucket, filled about halfway with water. The water itself is completely still. A perfect sphere with mass m and volume v are given. The depth of the water, and the radius of the bucket (which may be considered perfectly cylindrical) are both given. In short, you...
  20. Penguin98

    The thickness of glass and the longest wavelength

    Homework Statement In your research lab, a very thin, flat piece of glass with refractive index 2.00 and uniform thickness covers the opening of a chamber that holds a gas sample. The refractive indexes of the gases on either side of the glass are very close to unity. To determine the thickness...
  21. Samuel Williams

    Determine the Transition Wavelength

    Hi all, the question is as follows: 1. Homework Statement From the energy level diagram for OH in the study guide, it can be seen that the first rotationally excited level of OH (2∏3=2 J =5\2) lies 120 K above the groundstate. What is the wavelength of radiation associated with a transition...
  22. B

    Resonant Lengths in open air column question

    Homework Statement An organ pipe 1.2m long and open at both ends produces a note with the fundamental frequency. If the speed of sound in air is 345 m/s, what is the fundamental frequency? Homework Equations Wave equation (f = v/lambda) The Attempt at a Solution My textbook solves the problem...
  23. S

    Angle of Incidence, Propagation Constant and Wavelength

    Homework Statement Light of free-space wavelength λ0 = 0.87 μm is guided by a thin planar film of thickness d = 3.0 μm and refractive index n1 = 1.6, surrounded by a medium of refractive index n2 = 1.4 critical angle = 61.04° n0 = 1.00 (a) Determine (i) the angle of incidence θ and (ii) the...
  24. Amaterasu21

    I How can light have a wavelength or change direction in SR?

    Hi all, I have two questions about light in Special Relativity. (I'm going to pad these questions out with a few statements about my understanding of length contraction and time dilation, so you can see how I currently think about it and clear up any misconceptions if I've got the basic idea...
  25. enter

    I What is the highest frequency of electromagnetic radiation?

    Title says it all. Also, if the frequency of electromagnetic radiation is limited, why? My guess is the wavelength is limited to the Planck length, and when I plug those numbers into the calculator, I get 1.855 * 10^43 Hz. The maximum (Edit: observed) frequency of a gamma ray is 3 * 10^20 Hz...
  26. M

    Light wavelength transmission through ice

    I am studying hailstones. I have set up an experiment to pass colored light through hail, one color at a time for the colors of the visible spectrum, Red, Orange, Yellow, Green, Blue, Indigo and Violet (ROYGBIV). I have measured the dominate wavelength for each color with a photo spectrometer...
  27. Kenneth Boon Faker

    Why do cars crash? (Instead of passing through each other)

    If everything is made of atoms, and if atoms have so much empty space inside them - and if the building blocks of atoms are made up of wave-like particles that aren't solid (strictly speaking) - then why do cars crash and billiard balls bounce off each other, as opposed to passing through each...
  28. M

    Inteference Fringes of Double Slit Experiment in Water

    Homework Statement Suppose a double-slit experiment is immersed in water (with an index of refraction of 1.33). When in the water, what happens to the interference fringes? Homework Equations λ = λ0 / n y = (λmL) / d d = distance between slits L = distance to viewing screen n = index of...
  29. I

    What is the wavelength difference based on a mini spectrom.?

    Homework Statement I'm a bit stuck on how to approach this problem. A miniature spectrometer used for chemical analysis has a diffraction grating with 800 slits/mm set 25.0 mm in front of the detector "screen." The detector can barely distinguish two bright lines that are 30 μm apart in the...
  30. R

    Composition of Light

    Hi everyone, I have a few questions about the composition of light: First, what is it? Is white light the result of all color wavelengths present in an area? Second, if so, then why is there no interference in waves of light (or is there)? Third, if photons all travel at the same speed, then...
  31. G

    I How energy of light is conserved when passing through medium

    The velocity of light changes when it passes through a medium of a different refractive index. So let's suppose the light is traveling through a vacuum at a velocity c and then passes through a glass wall. Its velocity decreases while traveling through it but then speeds back up to c after...
  32. W

    Calculating Index of Refraction with Wavelength

    Homework Statement A beam of white light goes from air into water at an incident angle of 75 deg. What is the critical angle that the violet (410 nm) parts of the light is refracted? Homework Equations n1sin(θ1)=n2sin(θ2) n=c/v c=λf The Attempt at a Solution So sure, I get that the answer is...
  33. J

    B What is the relation between wavelength and orbital?

    I am in a chemistry class, and there was an in class example on how to do this type of problem, but then when I looked in the book, there wasn't an equation. the questions are related to what the wavelength will be when electrons are moving between orbitals.
  34. J

    B Size of wavelength

    Hey everyone hope you're doing well. I've always been confused about one particular aspect of electromagnetic waves. I understand that each frequency has a corresponding wavelength that is inversely proportionate and that the wavelength is the distance between successive crests or troughs. But...
  35. H

    How to find the wavelength of the sound of the tuning fork?

    Homework Statement 1) find the wavelength of the sound of the tuning fork (cm) 2) what's the vertical distance x from the top of the pipe to the antinode above the pipe (cm) 3) find the frequency of the tuning fork (Hz) Homework Equations velocity = wavelength . frequency for pipe closed at...
  36. S

    B If energy increases with decreasing wavelength, then..

    ..then a wavelength of zero nanometers has infinite energy?
  37. D

    What Is the frequency of red light?

    Homework Statement The speed of light in a vacuum is 3.00x(10*8)m/s. Using the equation v=fxλ, calculate the frequency of red-light. (I was told to use the wavelengths given from textbook) Wavelength/λ =700nm v=300,000,000 <-- ( I need help understanding this. Is this a rate? Or?) Homework...
  38. T

    I Radiation passing through Planck-scale wormholes

    This is something that has really been bugging me lately. There was a study from over twenty years ago that proposed that electromagnetic radiation might have been able to pass from one end of the universe to another in the early universe, furnishing an explanation for the homogeneity of the...
  39. W

    E = hf what sort of Energy is this?

    Homework Statement Is this E - say of an electron - the very E in E2 = (mc2)2 + (pc)2? If it isn't, what sort of Energy is this? Help is greatly appreciated! Homework Equations The Attempt at a Solution
  40. R

    Finding wavelength and fundamental frequency with string

    The length of a string is 1328 cm. It is held fixed at each end. The string vibrates in eight sections; i.e., the string has eight antinodes, and the string vibrates at 97 Hz. Find the wavelength and fundamental frequency. I have no clue, anything helps! Thank you!
  41. J

    Wavelength and Frequency in a Waveguide

    The problem states that the wavelength and frequency in a waveguide are related by: ##\lambda = \frac{c}{\sqrt{f^2 - f_0^2}}## then asks to express the group velocity ##v_g## in terms of c and the phase velocity ##v_p = \lambda f## Solution: Given that ##\omega = 2\pi f##, ## \omega(k) =...
  42. jwkhjang

    What's the relationship btw frequency, wavelength, and temp?

    I'm currently studying wavelength and frequency and I've learned about the equation v= f*Lambda. What will happen if temperature is changed? I know that speed of the sound will increase. Does it mean that wavelength will also increase? I was curious because if temp. increases, the frequency...
  43. J

    LED light wavelengths

    I work in a factory where we package pharmaceuticals. There are quiet a few products that are light sensitive to a certain wavelength. The lights in the older buildings are fluorescent and were have defined wavelength specification. The wavelength determined the color light/filters set in the...
  44. allenlistar

    Find the Wavelength

    Homework Statement A student collects diffraction data using a lamp with known emission wavelengths of 425nm, 565nm, 600nm, and 700nm. These lines appeared on her spectroscope at 32mm, 59mm, 63mm, and 69mm(all measured from the same arbitrary 0mm position). With these data she is able to...
  45. H

    I Energy associated with matter waves of macroscopic objects

    Consider an object of mass 1kg moving with a speed of 1m/s. Theoretically , the de broglie wavelength associated with it is about 3.6x10-37. Now if we calculate the energy associated with this wave it comes out to be 3x1011. This is a huge amount of energy which could be very hazardous but it is...
  46. T

    Change in energy as light passes through air/water

    Okay, best to provide some background here. I am trying to understand the light coming from the LED's over my aquarium. I have blue moon lights I think at about 540nm and 450nm. Oddly enough, when they are on, there is a green tinge to the light. I had assumed that this was because the light...
  47. K

    Sound frequency from distance b/w first minimum and maximum

    Homework Statement Two speakers are arranged as shown. For this problem, assume that point O is 12 m along the center line and the speakers are separated by a distance of 1.5 m. As the listener moves toward point P from point O, a series of alternating minima and maxima is encountered. The...
  48. H

    Finding Maximum Number of Interference Maxima?

    Homework Statement Light of wavelength λ = 535 nm shines through two narrow slits which are 670 μm apart. What is the maximum number of interference maxima which could conceivably be observed (assuming that diffraction minima do not extinguish them and the screen is arbitrarily large)?Your...
  49. vetgirl1990

    Finding wavelength from power

    Homework Statement The first unmanned probe will reach the stellar system of the Alfa Centauri (estimated radius 5x104 km) in year 2145. The probe will enter stationary orbit of radius R 300 x106km around the star. In order to power itself the probe will convert the radiative energy received by...
  50. M

    I Hydrogen Atom Photon Emission Wavelength Formula

    I am trying to calculate the Lyman-alpha wavelengths of photons emitted from different hydrogen-like atoms such as deuterium and positive helium ion 4He+, using the relation 1/λ = R*|1/ni^2 - 1/nf^2|, where R is the Rydberg constant and ni and nf are integer numbers corresponding to the initial...
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