# Questions tagged [wavelength]

The wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats, and the inverse of the spatial frequency or wavenumber. Determined by considering the distance between consecutive corresponding points of the same phase, such as crests. Use for wavenumber, wavelength, frequency.

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### Conceptual misunderstanding in Cauchy's equation in optics

We know that Cauchy's equation in optics is refractive index n = A + B/lambda^2 + c/lambda^4+ .... . But we also know that in any medium n = lambda in freespace/lambda in medium i.e n = A/lambda. What ...
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### How can spatial dimensions both expand and contract for the same observer at the same time?

Suppose a lamp emits a single wavelength (monochromatic light). The wavelength is A meters. Next to the lamp lies a stick, also of length A. Now we drive by the lamp at constant speed v, and then the ...
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### Vibrating string: why exactly these harmonics?

I read the following (informal) description of how harmonics arise when a string is plucked: How can you be sure that your guitar string is indeed just one continuous string, rather than two half ...
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### Wien's displacement law

Wien's displacement law states the following $$\lambda_{max}\propto\frac{1}{T}$$ However, after learning about redshift and blueshift, it doesn't make sense to me why we can use this law. Supposedly, ...
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### Physical basis of "forced harmonics" on a violin

I have recently learnt of a somewhat novel violin technique, sometimes known as "forced harmonics", where, in a physicist's terms, instead of the normal N=1 stationary wave (fundamental mode)...
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### Semiconductors and LEDs

My question is as follows, An LED, suppose say, red LED, has a single band gap, which may change subject to change of some parameters but, when I was measuring the intensities of the light of red LED, ...
1 vote
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### Diffusion of Electrons/Quasiparticles

I want to simulate the diffusion of electrons, or, more accurately, I want to simulate the diffusion of Bogoliubov quasiparticles. So I will break up some region of space into a fine grid and apply a ...
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### Can refraction change a wave's frequency?

Can refraction change a wave's frequency under any circumstances ? If yes, what conditions must apply for this to occur ? Is this a common phenomenon or only happening in extreme circumstances (such ...
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### Confusion about reasoning of black sodium flames

This video explains that a sodium flame absorbing the 590 nm wavelength looks black under a sodium lamp. Or to be more precise, the flame looks way less orange than the orange surroundings, since the ...
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### Continuous $4\pi$ steradian monitoring of space

What would it take to constantly survey space at a selection of frequencies? I'm imagining a set of satellites pointing away from the Earth and scanning all sectors of space. Can anyone point me to ...
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### Could someone explain to me why my approach here is wrong? [closed]

The area of the central maximum produced by a circular aperture is $8.25*10^{-6}$ m$^{2}$. If the aperture is 1.2 mm in diameter and the screen is 3 m away from the slit, what is the wavelength of the ...
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### Why is $(m-1/2)λ$ used here and not $(m+1/2)λ$?

A light beam illuminating a double slit consists of two wavelengths, 620 nm and an unknown wavelength λ. The 8th bright fringe of the unknown wavelength overlaps with the 7th dark fringe of the 620 nm ...
1 vote
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### Why can't one-way speed of light be derived with simple wave mechanics? [duplicate]

If we understand light as having a frequency and wavelength, why not just multiply them to get the speed, this doesn't require mirrors or synchronised clocks. I'm 100% sure this doesn't work, but I ...
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### What is the frequency of a standing wave? [closed]

I understand that constructive interference of waves results in standing waves. And for a wire with both ends fixed the frequency should match the fundamental frequency of the wire to produce standing ...
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### What is the mathematical support for the formula $f_n = n f_1$, used to calculate the frequency of a standing wave? [closed]

could someone explain to me the mathematical support for the formula $f_n = n f_1$. This formula refers to the fact that the frequency of a standing wave is equal to the number of antinodes times the ...
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### Why does the length of an antenna matter when electromagnetic waves propagate perpendicular to the antenna?

The optimum length for a dipole antenna is a multiple of half the wavelength that it is designed to receive or emit. Why is this? If an electromagnetic wave has E in the x-axis, B in the y-axis, and ...
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### Understanding Loop Formation in a Plucked String

I have a question regarding the formation of loops when a string is plucked at different fractional lengths. In a book I referenced, it is stated that plucking a string at 1/6 of its length produces 3 ...
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### At which wavelengths do photons behave like X-ray?

Hard X-rays of wavelengths of about an angstrom are very different than regular lights in a way that they can’t be reflected or refracted, which means their refractive index is always close to 1 ...
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### Can the laser light, in principle, take any wavelength in the EM spectrum?

Can the laser light, in principle, take any wavelength in the EM spectrum? I don't think there is what prevent this in principle, right?
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### How can photons interact with nuclei?

How can photons such as X-rays or gamma rays interact with the nuclei of atoms given that, as I understand it, the length scale of a nucleus is around a couple of femtometers? So, shouldn’t the size ...
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### Why does oxygen green (S1) emission in aurorae only occur at lower altitudes? [duplicate]

Aurorae have a red color at high altitudes caused by the excitation of atomic oxygen and the subsequent emission at about $630 \,\text{nm}$. This happens at high altitudes because at that height there ...
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### De Broglie wavelength and how it leads to the wave function

From what I know, de Broglie derived the wavelength equation using Einstein's $E=mc^2$ and the Einstein-Planck equation $E=h\nu$. My teacher explained this by saying an electron literally moves in ...
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### Minimum frequency for a dipole antenna to work

Does a dipole antenna need a minimum frequency of AC to make the electric field detach and propagate?
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### What do the $x$ and $y$ axes mean on a chromaticity diagram?

I understand that the chromaticity diagram is a plot of visible wavelength colors. Since the visible wavelengths form a curve on the graph, what do the $x$ and $y$ axes mean? My thinking could be ...
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### Interpretations of wave numbers between open and periodic boundary conditions

I'm curious about the difference in physical interpretation between open and periodic boundary conditions (OBC and PBC) although they are identical in the thermodynamic limit. For simplicity, let's ...
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### What is a laser spectrum?

What is a laser spectrum? How many wavelengths can we see in it, and why? For a regular laser, the red ones you can buy at the store, is there just one red wavelength in the laser? Or are there ...
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### What is the upper limit of size for diffracting an object?

All items in the universe can be said to have a De Broglie wavelength which is significant if that wavelength is comparable to the object's size (I don't have to worry about my wavelength diffracting ...
1 vote
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### How is wavelength defined when it's changing continuously?

Take an observer, who is receiving an electromagnetic wave signal, which is constantly changing. It can be for example from a source of light falling into a black hole, so the observed wavelength is ...
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### Emission spectrum of a fluorescent lamp

I had to analyze the emission spectrum of a compact fluorescent lamp and find what elements are present in the lamp, based on the spectrum of spikes in wavelengths. Knowing that in our lamp there was ...
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### What would happen if my body de Broglie wavelength is significantly large? [duplicate]

I have a question that what would the world be, if matter de Broglie wavelength was large?
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### What's the difference between the different kinds of EM waves?

I am an A-level student. We have traditionally been taught that different types of EM waves exist only between certain ranges of wavelengths and frequencies. However, I learned that electromagnetic ...
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### Who wrote $c = λ ν$ for the first time and where can I find it?

I have been surfing for days and still I could not find who wrote the equation $c=λν$ for the first time. Neither I found a name for this equation. A lot about Planck's constant and energy related ...
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### Is this image on harmonics and overtones wrong?

I saw this image and believed this to be the definition of what the relationship between harmonics and overtones to be in strings, closed pipes and open pipes. That the $n^{th}$ harmonic = $n-1^{th}$ ...
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### How many 'wavelengths of length' can a wave have? [closed]

Since a wavelength, $\lambda$, is the length of a entire cycle How many $\lambda$ (complete cycles) can a composed wave have? I mean, for $n \lambda$, how big can $n$ be? And what does it mean, ...
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### Ultrasonic whistling

My friend from physics who doesn't know whistling says he is good at whistling, but the resonant frequencies are ultrasonic so others cannot hear it. Could this be right, or is he just bluffing? ...
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