Spectrum Definition and 725 Threads

Hello, I am currently analysing some relfectance data I obtained from measurements on several silicon samples. During the process I used the standard fresnel coefficients, and suddenly I began to wonder, what the peaks describe? The last graph at this link shows it for normal incident light...

Dear Experts, I try to understand power spectra for large scale structure and CMB analyses for my exams. I constantly find the expression for linear power spectra P(k) = A\cdot k^{n_s}\cdot T^2(k). I understand that this comes from primodial primodial fluctuations and the tranfer function...

Homework Statement You decide to become a forensic pathologist because you enjoy working with dead people-they don't talk back-more than with the living. In one murder investigation, you find an unknown liquid in the victim's stomach. To identify this liquid, you pour a known amount of it onto...

Something that bugged me when doing this lab. Standard little glass vials of gas, toss it in a 5kV potential make pretty color, look through diffraction grating see the individual wavelengths that are the finger prints of the element. My question however are all wavelengths equally...

why does the continuous emission spectrum depends only on the temperature of the solution and not on the characteristics of the source?i could not understand this.someone please explain me this:rolleyes:

Greetings, I must be missing something obvious but how is Tr{} defined exactly in case of contunuous spectrum operators? Everywhere I look I see it defined as a sum of [possibly infinite sequence of] eigenvalues. Is the following correct: Given Q = \int f(q) \left| q\right\rangle...

Homework Statement Use the simple model for electromagnetic showers (explained below) to show that the energy spectrum of all secondary particles contained in an electromagnetic shower falls like E^{-2} for E_0 >> E >> E_c The Attempt at a Solution An electron or a photon with energy E_0...

I read that many high pressure sodium and high pressure mercury street lights are being replaced with much more efficient LED lights, which fortunately point downwards instead of sending light sideways at star gazers like me, or into the sky where it refracts back down and hazes over the stars...

The visible spectrum of light from hydrogen displays four wavelengths, 410 nm, 434 nm, 486 nm, and 656 nm normally. Which changes when a telescope is pointed at a Galaxy that is moving away?

What is spectrum? Today my teacher started the class by saying we are going to see about spectroscopy which deals with interaction of electromagnetic radiation with matter and there are two types of spectrum the atomic spectrum and the molecular spectrum. He didn't even say us what is...

Homework Statement Find the spectrum of the Momentum operator in the Hilbert Space defined by L^2([-L,L]), consisting of all square integrable functions ψ(x) in the range -L, to L Homework Equations We can get the resolvent set containting all λ in ℂ such that you can always find a...

Homework Statement Make a sketch of the spectrum of the signal defined by: x(t) = \sum_{k = -3}^{3}\frac{1}{1+j\pi k}e^{j4\pi kt} Use polar notation for the phasors on the plot, and sketch the frequency axis in Hz. Homework Equations The Attempt at a Solution a_{k} =...

In electromagnetic spectrum, why there is no radiation less than wavelength of Gamma rays and waves higher than the wavelength of Radio waves?

If I posted in the wrong section, please feel free to move the thread in the correct one. Since this is my first post in the forum, I have yet to get a good grasp of it. With that said, let's begin! Prologue: SNR (Signal to Noise Ratio), sometimes indicated with S/N, is a very important...

Homework Statement The emission spectrum of an unknown element contains two lines - one in the visible portion of the spectrum, and the other, ultraviolet. Based on the following figure and what you know about Niels Bohr's model of the atom, account for the difference in energy between these...

Hi. I read some basic cosmology where it is always said that density fluctuations, pertubations can be described in modes of waves. In particular if you use linearised theory where δ(x,t) is Fourier transformed δ(k,t). What exactly is the reason for this? What do the wave modes describe...

I've often read that the emission spectrum of a fluorescent molecule is independent of the wavelength used for the excitation. But what happens in the case of a small Stoke's shift where the excitation and emission wavelengths overlap? If I use a narrow band excitation with a wavelength in...

I am working on my thesis for my masters in physics, and am running into some issues while trying to gather an IR spectrum of my hydrogenated amorphous silicon (a-Si:H). I am depositing my films using PECVD onto a glass microscope slide substrate. The films I have used so far have been 0.2-0.4...

I Watched A Video . In Which , It's Mentioned That The Relative Size Of.. Gamma Rays - Atomic Nucleus X-Rays - Atom Ultra-Violet Rays - DNA Visible Light - Bacteria ... Radio Waves - Mountain Ranges What's Mean By Relative Size ? I'm Confused Alot ! Thanks Alot In Advance For...

Hi, I would like to do more studies and research in electromagnetic spectrum. And I am interested very much in these waves and it's interaction with human or living things or matter. So please provide me with the information about what kind of courses I should take. I will complete my post...

why doesn't the uncertainty principle lead to small discrepancies in the spectrum of the same element in different situations? I think that since there is a whole area for the electron to jump from and to and therefore a small range of values of possible jumps for a single shell, so there...

According to the Einstein light-quantum hypothsis, the photon energy is given by E = hbar*ω. If taking the photon as a very short light pulse, then the frequency spectrum is extremely wide in terms of Fourier-transform theory. How to understand the frequency ω in E = hbar*ω if taking the...

Homework Statement I am trying to figure out how to graph the signal spectra of an AM signal where the message m(t) is multiplied by the carrier, which is sin^3 (wt) instead of cos (wt). I can do the FT but I do not know how to graph this since there are imaginary numbers as coefficients...

Hello, Something I have some time wondering and still couldn't find the answer is to this question: if there is some relation between the Spectrum (functional analysis) and the Frequency spectrum in Fourier Analysis. Now that I think about it there seems to be a casuality the use of the...

Hi everyone, So I'm trying to basically generate a list of numbers between 20 and 20,000 (Hz) in log space that will give good resolution to parts of the audio spectrum that matter! After all that is the point of using log scale for frequency in the first place. The list generator I have...

I have an x-ray tube. When I see the spectrum, I notice the characteristic lines of the anode. What do I have to do if I want to absorb a characteristic line? I have thought that I can add a filter. But.. which filter? Should it be an element such that the bound energy for the K-shell electrons...

Homework Statement Show that in the Bohr model, the frequency of revolution of an electron in its nth In classical physics, the frequency of revolution of the electron is equal to the frequency of radiation it emits. Show that when n is very large, the frequency of revolution is equal...

Homework Statement The following photon wavelengths are observed in absorption at room temperature from an ionized atomic gas with a single electron orbiting the nucleus: λ= 13:5 nm, 11:4 nm, 10:8 nm. Use this data to determine the effective Rydberg constant and the nuclear charge...

I know in ordinary QM, the spectrum of the Hamiltonian \{ E_{n}\} gives you just about everything you need for the system in question (roughly speaking). So what happens to this spectrum in QFT where |\psi\rangle is now a multiparticle wavefunction in some Fock space? I've been trying to...

I'm trying to understand the spectrum and resolvent of a linear operator on a Banach space in as much generality as I possibly can. It seems that the furthest the concept can be "pulled back" is to a linear operator T: D(T) \to X, where X is a Banach space and D(T)\subseteq X. But here are a...

What is the distinction between EM waves and Sound waves. I know that sound is cyclical vibrations in some sort of medium. When the frequency increases, do these vibrations become EM waves? I know that EM waves do not need a physical medium. But they are still energy, and sound is energy. So...

Hi, I have troubles understanding the difference between linear and non linear matter power spectrum. These words are commonly used in the litterature, but I have found no definitions yet. My understanding is that there is one definition of the power spectrum for matter distribution...

When doing an experiment in order to observe the atomic spectra of some gas. We observe while peaking through the diffraction grating, symmetrical lines starting from n=1. Where does this symmetry arise from? Why do we see the same spectrum repeated on both, left side and right side. As if...

Hi I want to define an Am-Be source in MCNPX 2.6 I have Neutron spectrum But I don't have Gamma spectrum of this source. Please Help!

Hi, I've been trying to understand DSSS, but I'm not an engineer and have trouble with one point. I get the fact that multiplying the user signal with the chip sequence is what spreads the signal. My question is, why is this? If the data rate is, say, 1 bps, and the chip sequence 1000 bits...

Hi couldn't find a similar thread so thought i'd make one. I keep seeing around the web that the far-UV spectrum is unobservable (context is looking at the spectra of AGN) but no-one seems to explain why. I think that its something to do with hydrogen strongly absorbs at these wavelengths...

The discrete-time spectrum of a sampled continuous-time signal x(t) is shown in the figure above, where (A = 9.8exp(-j0.06π), B = 0.51π, C = -0.27π, and D = 1.9exp(-j0.41π) ). If the sampling frequency is 4928, which of the following continous-time signals is a possible solution for x(t)...

Hi everyone, I am using a signal generator in series with a RLC circuit, generating an AC signal at 1kHz. I have my probes connected across the resistor When I change the timescale the Fres bandwidth changes on the spectrum analyzer. At 1mS the resonant bandwidth is from 25kHz-50kHz At...

Homework Statement When an electron drops from the M shell (n = 3) to a vacancy in the K shell (n = 1), the measured wavelength of the emitted x-ray is found to be 0.0897 nm. Identify the element. Homework Equations E = 1240 / λ E = (-13.6 / n^2) * (Zeff^2) The Attempt at a...

hello all. If one uses polarization modulation of radio waves does this imply a broad frequency spectrum knowing the carrier frequency and amplitude remain the same only the direction of the electric field is being changed ?

Negative frequencies in spectrum analysis... Hello everyone... When we do the frequency analysis of a signal using Fourier transform, we get spectrum at negative frequencies also. What are they and what is the physical significance of such frequencies? Its hard for me to imagine a negative...

I mean why is it that the eye evolved to detect "visible" light instead of, say, microwaves. What is it about the visible light spectrum?

This is a question about the proper form for thermal noise from a resistor. This is purely academic for me - I always work in the regime where \hbar \omega << k T so the noise spectrum is simply P \approx kT. When this no longer holds, quantum effects matter of course. Then I have seen...

From what I've learned in physics, electrons falling from higher energy levels to a lower energy level emits an photon equal to that of the difference in energy between the two levels. Each atom has a set number of energy levels for the electrons, and thus each element can only emit a set number...

I have an unidentified radiation source. I used a NaI(Tl) detector and multichannel analyzer to collect data and plotted the spectrum. I found peaks at energies of 86.3, 123.7, and 369.6 keV. From this data I am attempting to identify the source, but I am having a difficult time. I tried using...

on a visible spectrum scale what are the numbers for the colors of ROYGBIV? for example is violet 400-500nm and red is 700-800nm? how about the other colors? If the energy of a photon is 2.63 x 10^-19 J, how can we tell what color this is? i was looking at this electromagnetic spectrum and it...

Consider an unbounded self-adjoint operator defined in a hilbert space(its domain isn't the entire hilbert space,of course).Can its spectrum have discrete and continuous parts simultaneity?Does it have eigenvectors with finite norm? Thanks

Homework Statement I need to explain DSSS in my applied mathematics project (duration is three minutes of my talk). How do two users agree on which channel and the time to listen to so that they can exchange messages? Homework Equations Use Barker sequence as a channel encoder and...

Homework Statement A sensor yields a signal y(t) = |sin(120\pit)| a. Using Fourier analysis please construct an amplitude spectrum for this signal. Homework Equations A0 = \frac{1}{T}\int ^{-T/2}_{T/2}y(t) dt An =\frac{2}{T}\int^{-T/2}_{T/2}y(t)cos\frac{2n\pi t}{T}dt The Attempt at...

How can discreet quanta of photon energy make up a continuous electromagnetic spectrum, whose wavelengths are any arbitrary value? Is there overlap of quanta, temperature dependency, or so many finely divided energy levels that the spectrum just appears continuous? Electron energies are...