# 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. ### Colour depends on wavelength or frequency?

This is the Question: It's from the book: Concepts of Physics by Dr. H C Verma. The common observation is off course that a red light would appear red even when viewed from under the water (for eg in a swimming pool). But, in the same book, it's been written that colour depends on wavelength...
2. ### B What sound frequencies can pass through a hole in a wall?

Hello, First of all, I will try to overcome language barrier as this is not my native language and the more topic is scientific - the more chance for me to get lost in translation. Apologies for poor grammar in advance. I marked it as Advanced post, so apologies if this has to be corrected by...
3. ### I De Broglie Wavelength at rest: λ = h/p = h/0 when v=0?

De Broglie Wavelength is λ = h / p. So at rest, v=0, and p=mv, so p=0. This means that λ = h/p = h/0 so we run into a divide by 0 issue, or infinite wavelengths for objects at rest. Is this line of reasoning flawed? Or can we consider v=1 for rest masses? Time Dilation is related to v. The...
4. ### Wavelength / signal which would pass through concrete and rubble

Greetings, Please imagine a huge pile of rubble, meters deep. Somewhere inside, there's a device emitting a certain signal. This signal can be picked up by a radar-like device which locates the origin of that signal, with the least interference from the pile of rubble, concrete blocks, metals...
5. ### What Is the Maximum Wavelength to Break the Weakest Bond in AsClF42-?

Mentor's Note: Post moved to homework forum from chemistry forum. Hello, I have a doubt in anexercise from MIT: -------------------------------------------------------------------------------------------------------------------------------------------- Calculate the maximum wavelength, λ, of...
6. M

### Measuring wavelength of microwave radiation using double slits

For this problem, The solution is, However, when they found the angle, they did not account for the uncertainty. I guess this is allowed still since the sine of the angle will still be greater than 1, correct? Many thanks!
7. ### Calculating Wave Amplitude & Wavelength in Water Pools

How would we model/calculate the circular waves in a pool of water (wavelength and amplitude) from a mass falling into it from a given height, and from a fountain of water falling into it continuously? Is there is a way to describe the initial configuration of the wave based on the stimulus...
8. ### I Why can't objects be seen if the wavelength is too long?

Sorry, this has been asked a few times, but nothing's getting through to me. I really need to satisfy this curiosity :( I've read a lot of "water wave" analogies, but they don't make sense. A water wave has physical peaks and valleys, and I can see how when the peak travels and hits a ship, the...
9. ### I How to emit 3.2 micrometer wavelength

Good day! Can anyone tell me how to emit a 3.2 micrometer(μm) wavelength with as much energy as possible? How could it be "homemade"? Is it possible? Thank you so much
10. ### B Time Dilation & Muon De Broglie Wavelength: Explained

I understand it's experimentally verified muons traveling at relativistic speeds relative to an observer will be observed to have longer half-life than would be observed in the rest frame of the muons, which is explained theoretically by a relativistic time dilation effect. Does this correspond...
11. ### I What wavelength can penetrate soil to 15 feet?

As my name suggests I am a gold prospector. My question is what wavelength would penetrate 15 feet of soil, sand, and clay but be stopped when it struck gold? The goal is to create a device that will allow for looking into the ground in such a fashion as to be able to create a visible display...
12. ### B Wavelength of a laser beam emerging from a prism

Summary:: If you send a laser beam through a prism, can you measure any shift in wavelength at the other side of it? This sounds like a high school experiment and the concept is simple. I feel the laser should emerge monochromatic and at the same wavelength it went in. Do you get this result...
13. ### 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...
14. ### 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...
15. ### B Speed of light versus wavelength

We know the speed of light is a constant but speed is just the measure of distance over time. If blue light has a shorter wavelength than red but covers the same distance / time does this mean that blue light has actually made a longer journey than red light in order to arrive simultaneously? I...
16. ### I Quantum spin, wavelength and frequency

Greetings, I'm new here, I have an interest in the nature of reality, and a question. Does the quantum spin of a particle (its intrinsic angular momentum) have anything to do with its wavelength and frequency? One of the experts on Quora said no, and I cannot find anything about it on the web...
17. ### I Wavelength of Light Ray Affected by Gravity

I was reading Einstein's 1911 paper named "On the Influence of Gravitation on the Propagation of Light" when stated the formula for frequencies measured by observers at different fixed positions (heights) on Earth surface. One observer is at the origin of some coordinate system and measures a...
18. ### 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...
19. ### How Does Lorentz's Equation Transform into Cauchy's Law?

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...
20. ### Solving Destructive Interference: Angle vs Wavelength

The destructive interference equation for small angles is angle=wavelength/(2a), where a is the width. I assume it means destructive interference since its talking about areas where no light is present. Using the equation after changing degrees into radians I get the answer of 2491 nm when the...
21. ### Engineering Optical Fibres: Wavelength for Zero net Dispersion

Hi, I was working on the problem below: Question: An optical fibre transmission system uses a step-index multimode optical fibre which has a core refractive index of 1.49 and a cladding refractive index of 1.48. The fibre is also subject to material dispersion which is a function of wavelength...
22. ### I How do I properly plot the solar spectrum and handle the flux of Arcturus?

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...
23. ### 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?
24. ### Wave, given wavespeed, wavelength, amplitude - find w.

What I chose to do was analyze what happened at x=0. At x=0 I know sin of whatever will be 0. So 0=sin(kx-wt) and since x=0, w=Arcsin(0)/t. But this doesn't make sense because the answer isn't 0, its 0.695.
25. ### 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...
26. ### I Wavelength and size of holes or grating

Could someone explain to be the reason why size of the hole or grating in the case of Faraday cage is what determines if the screen or grating is opaque or transparent? I'm pretty sure it has something to do with interference patterns in classical physics. Thank you all in advanced.
27. ### Simple Wavelength Problem (wire of fixed length vibrating)

When the question says 8 antinodes, doesn't that mean N=8? but when I do 2L/8, I get 0.24. To get the right answer you do 2LN, but that doesn't make sense to me for I thought the equation was 2L/N??
28. ### I What is the Fermi wavelength of a graphene lattice in the tight binding model?

I am trying to figure out what the Fermi wavelength of my system is. Specifically I am looking at simulation a graphene lattice in the tight binding model. For this, I know that the Fermi energy (undoped) of my system is 3t (for simplicity I set t = 1). But how do I figure out what the Fermi...
29. ### Wavelength of a transparent medicine

Summary:: Is there a way to find the wavelength of a transparent medicine without adding a color to it? I have a transparent substance (medicine) . I cannot find out its wavelength without having to add color to it. However I don't want to change any of its characteristics. Is there a way to...
30. ### 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...
31. ### Calculate Wavelength Without Frequency

n1sintheta1=n2sintheta2 1*sin36=n2sin24 n2=sin36/sin24 n2= 1.45 to calculate wavelength is lambda=c/f My question is that that how do I find the wavelength without given the frequency.
32. ### 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...
33. ### I Lyman-##\alpha## Wavelength: Hydrogen's Region in Spectrum

I am learning about the hydrogen atom and in my book it discusses the Lyman-##\alpha## wavelength and I am wondering in what region in the spectrum is the Lyman-##\alpha## for hydrogen?
34. ### 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...
35. ### B How can we measure the wavelength of gamma-rays?

How can we experimentally measure the wavelength of gamma-rays, say for about 0.7MeV? Can it be done without gamma-ray spectrometry?
36. ### A Upper bound for wavelength of a photon inside an infinite square well

Obviously a particle inside an ISW of width L cannot have arbitrarily precise momentum because ΔP ≥ ℏ/2ΔX ≥ ℏ/2L. Therefore you cannot have a particle with arbitrarily low momentum, since that would require ΔP be arbitrarily small. I need to show that a photon inside an ISW cannot have...
37. ### 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...
38. ### I Photons and wavelength in ultrafast optics

I am not understanding how to think of photons and wavelength in ultrafast optics. An ultrashort pulse is the summation of many wavelengths. So, if you refract an ultrafast pulse it will actually spread out spatially? Can you define a wavelength as sort of an average wavelength? And most of the...
39. ### B Does Motion Affect Perceived Wavelength and Light Speed?

[Mentors' note: This thread has been moved from the relativity forum, as it is a question about the classical behavior of waves] Is the length of a beam of light the number of crests times the wavelength?
40. ### What is the Wavelength of Corona Discharge in High Voltage Testing?

Hi, I am doing high voltage testing (20-35 kV or more) where I am trying to capture corona discharge. My DUT is in a dark test room with no light. I am using a Canon EOS T7 (2000D) DSLR to capture the corona. What I would like to know is the wavelength of the corona so I can do further...
41. ### I Converting "Luminosity per unit wavelength" to "Luminosity per unit frequency"

If there is a luminosity per unit wavelength defined as L_λ dλ, am I correct in thinking that the conversion to luminosity per unit frequency (L_ν) would be L_ν = L_λ (λ^2/c)? And building off of that, if the shape of a spectrum was proportional to a power-law: L_λ = λ^(β), is there a way to...
42. ### Change the wavelength in a driven rope?

I think I know what this problem means, but not sure how can I do quantitative work to solve it. I think only a would work because of friction of string, the reflected waves from the junction between two strings like that. Although, I am not sure how can I build the process, but this was my guess...
43. ### Light interacting with Matter -- Does the wavelength make a difference?

I heard somewhere that light in the visible spectrum that we see interacts with matter the most? Is that true, and in what ways?
44. ### How Do You Calculate Neutron Wavelength?

λ^2=h^2/m^2v^2 =h^2/2/(m^2v^2/2) =h^2/2/(Km) =h^2/2Km
45. ### B Are electromagnetic wavelength and quantum wavelength the same thing?

The classical picture of the electromagnetic wave has electric and magnetic field oscillations which give the wavelength of the light. In the quantum picture, is the wavelength of the (de Broglie) wave function of the photon the same thing?
46. ### 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...
47. ### 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...
48. ### How is the wavelength of emitted EM radiation measured?

Hi, Source: https://en.wikipedia.org/wiki/Second#"Atomic"_second How were such huge number of periods per second measured originally? Was an instrument such as Michelson interferometer used? I think it was Albert Michelson who invented the interferometer to make calculations of wavelength and...
49. ### Can a Single Point Grapefruit Create an Interference Pattern?

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 *...
50. ### B Relationship between wavelength and concentration of particles

What is the relationship between the wavelength produced by a laser and the concentration of particles in the air? Does the wavelength get larger if the concentration of particles the beam hits increase?