Spectrum Definition and 725 Threads

Hi, When a molecule makes a transition from high energy state to low energy state, it emits electromagnetic radiation with a certain wavelength, which can be collected as emission spectrum. However, I have a question right here: For any real case, there are quite a number of molecules in one...

Carver Mead writes in his book, "Collective Electrodynamics", that experimental evidence indicates a superconducting ring and capacitor resonator circuit will increase from zero voltage (scalar potential difference) to an energy matching a 3 degree Kelvin black body radiation spectrum...

I understand why a black body absorbs every frequency(it is the definition of a black body!) but i do not understand why it also radiates at all frequency spectrum.

The FCC's propagation models for the FM broadcast band seem grotesquely inaccurate in some places, where stations can be received that the models say are absolutely out of range. I'm not even talking about DX conditions like ducting or skip, I'm talking about baseline. When I lived in...

Now that, in bound state, the particles have quantized energy. So the system can only absorb certain kinds of photons. But why when I see the absorption graphic in books(x-axis is wavelength; y-axis is intensity, transmission percentage or sth), they are all continuous? They do have peaks...

I understand that the result of the hydrogen emission spectrum experiment was that only certain wavelengths of light were emitted and that led to the conclusion that electrons emit light when they relax and that they absorb light when they get excited. How does that prove that the energy for...

Hi, Is there any known ways in Physics how to convert Red light to blue?

I'm learning digital signal processing in my engineer class, but I'm more interested in apply these things into Astrophysics, so i know a little bit about for what is useful the Fourier Transform, so i thought why not use this in Analyzing the sun spectra! But what do you think!? Is it useful...

Hi all, A question about the vacuum energy density and spectrum. The only spectrum that is frame invariant involves the cube of the frequency. Is it also possible to have a constant offset term (which would also be frame invariant), to 'adjust' the energy density so it doesn't turn out to be...

Folks, I am looking for a more intuitive explanation of why water is transparent in the visible range. I am looking for the mechanism -- clearly it is transparent because photons are not absorbed. However, I am clueless as to why water should strongly absorb microwaves due to its polarity but...

Hi, I am just trying to understand the output of a sound spectrum analyzer. There are three dimensions 1) Time 2) Frequency 3) Volume (db) I am confused about few things here: 1) How should I perceive the volume dimension here? 2) Why are the db values negative here and w.r.t what reference...

Hi all, I have been getting the emission spectrum of a polymer for a while. The emission peak is very important for that polymer. How do I find the emission peak of the polymer? The reason I ask this question is that if I simply select the highest point, then several points at different...

Can someone tell me how i can determine the one degree peak from power spectrum ?

Homework Statement I have been investigating the Doppler effect in a circular motion with a stationary source and moving observer (however the main aim is to determine the speed of sound in the end). Using Vernier software - Logger Pro - I have obtained two graphs of the sound pressure against...

I was looking around for information on the electromagnetic spectrum, but I have found some sources saying there is a new part of it called "terahertz", which would be between infrared and microwave. I have found some sources, but I don't really believe them so. Here are some sources of what I...

hello every one , I want to know how we get phonon frequency spectrum theoretically by using three modes and dispersion relation, can anyone explain it. for example it is phonon energy correspond to density of state how it is obtain?

I constructed my code of the Angular Spectrum Method. However, as the distance between the object and the plane of interest increases, the diffraction pattern never disappears; there is still some sort of a diffraction pattern, and I am expecting that it disappears as distance increases. Here...

it is said that the energy spectrum of two body and three body decay is discrete and continuous respectively.

Supposed to be because they have a zero dipole moment... Dipole moment is variously described using neutral systems of pairs of opposite charge, or single items with charge, but I am finding no explanations of same charge pairs I understand.. Wiki states: "To show a vibrational spectrum, a...

I'm looking at a program for Monte Carlo simulation of electron trajectory in a matter. When I look at the detected X-ray spectrum, there are two distinct curves, one called "characteristic", the shape of which is peaky. The other is called "background" where the shape is continuous. My...

Looking for typical experimental parameters for measuring emission spectrum of both H and H2, specifically gas pressures. Also would like to know typical pressure range where spectrum transitions from H2 to H. Thanks.

I am using Renishaw confocal Raman microscope to do photoluminescence spectroscopy of some polymer inside microchannel. When I fix the laser power and exposure time, the absolute count of intensity will change from time to time even for the same sample. I was hoping the intensity should linearly...

I am using a Renishaw inVia confocal microscope to study emission spectrum of molecules. The excitation wavelength of laser that I use is 532nm. However, I met with a very basic problem. When I use the same material (say plain silicon), and use different objectives (20X, 50X, 100X), then I will...

Hi fellas! I am planning to start a ISP in our region, which uses cellular tower for bandwidth signal receiving & transmitting. We have established the leased line back bone to our network and figured out microwave & GSM antenna concepts to receive signals from suppliers and to send signals to...

Homework Statement A zeeman experience is made in the transition 3s4s ## ^3S_1## -> 3s3p ##^3P_2## in Magnesium with a magnetic field of 2Teslas (20 000 Gauss). With no magnetic field the emission occurs in 518.360nm. a) Draw the spectrum of what you hoped you observe when you're watching the...

Hi every one, What is the smooth gamma ray energy spectrum in gamma radiation? And, What is the algorithm of smooth gamma spectrum? Thank every one to much!

Are the results of the Angular Spectrum Method and the Fourier Transform of a Fresnel Diffraction be different, or the same? Given the same distance between the input and output plane, and the same aperture.

In the book "Statistical physics for cosmic structures" at p. 171 a read a definition of scale invariance (leading to the so called scale invariant power spectrum) given as the requirement that ##\sigma^2_M(R=R_H(t)) = constant##, where ##R_H(t)## is the horizon, i.e. the maximal distance that...

Homework Statement Why do supposedly forbidden transitions appear in experimental spectrums? Homework EquationsThe Attempt at a Solution I'm really puzzled as to why they appear. Can it be due to transitions on higher energy levels that happen to be equal to the forbidden ones?

Suppose you are given a phase spectrum or (/and) equation of the (main) signal only and you are said that the given (main) signal is formed of 3 other signals. Is it possible to compute phases of these three signals from the equation or (/ and) phase spectrum of the (main) signal? Also,what...

Hey! I've a simple (and maybe stupid) question about the accuracy of an OSA. The datasheet report a level accuracy of 0.4 dB but this seems quite strange to me. Indeed level measurements are done in dBm thus, as long as dB measures a relative power, I assume that even the 0.4 dB are referred to...

I'm interested in rainbows. I'm talking about good old fashioned arc/halo rainbows like those you see in the sky. Sometimes you see rainbows from lawn sprinklers. How small would the smallest rainbow arc conceivably possible to view be? Could I make a rainbow at night using a sprinkler with a...

If I have the energy value (in cm-1) of a specific line in the rotational spectrum, how do I find out/assign the correct J''-J' values? I know the selection rules for J to be +/- 1 for each rotational transition but I'm not sure how you can correctly identify which J value it is if your only...

For years, I've been tinkering away at an idea for a superhero. Without going into too much detail, I thought it'd be cool if he could tap into, control, and even travel through a number of different types of signals: radio signals, satellite signals, wi-fi, etc. Using brain waves, as well, I...

Hi there, I'm trying to clear up some misconceptions I have about emission spectra from various substances. Most of the discussion about gases focusses on the line emission spectra from a hot, low density gas due to electron shell transitions. But I also know that any charges that are made to...

Hi all, I've got two questions about the emissions spectrum from solids. Question #1: I feel like I have a reasonable understanding of line absorption and emission spectrum of low density gases based on transitions of electrons between discrete allowed energy levels in a gas. I'm trying to...

Would someone please tell me what an extinction spectrum refers to? e.g. for plasmonic gold nanoparticles. Is it the same thing as reflection, absorption, or transmission spectrum? Something else?

I can't seem to find an answer to this quick question: which part of the star causes the observed spectral lines? As I understand, the photosphere is the deepest visible layer of the star, and then light passes through the chromosphere and the corona. I would think that both the chromosphere and...

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)...

So, this is something I've never understood in detail. If an excited system decays and emits a photon, the lifetime of the decay will broaden the spectrum of the photon right? Basically just a Fourier transform of the "shape" of the emission in time to get the frequency components of the...

When I observe the UV light emitted, I can literally see the millions of photons appear and die within milliseconds, but nobody else around me can. When I observe IF light sources and transmitters in low light, it is the same characteristic, except there only appears to be to photon sources, and...

Homework Statement In the spectrum of the blue part in a candle flame, there’s a violet emission at 432 nm due to excited CH* molecules (chemiluminescence). Why 432? Why not 400 or 500? There are emissions at 436, 475 and 520 nm too. Why these numbers? 2. The attempt at a solution Is it...

I understand that when light goes between air and water, refraction occurs (either towards or away from the normal). If the light going between air and water is already going in the same direction as the normal, is there no refraction (or a refraction angle of 0 degrees)? Thank you.

Hello, I have heard many times that red lighting is good for imaging applications where the effect of ambient light needs to be reduced to a minimum. What is the theory behind this? Why does red light (vs. other colors) reduce the effect of ambient light? Thank you.

Hello forum, The reflectance spectrum has % on the vertical axis and wavelength on the horizontal axis. A red object is red because it reflects all the red light and absorbs all the other wavelengths of the white incident light. If the read object was ideal, would its reflectance spectrum be...

Is it true, as someone says, that molecular hydrogen in its fundamental state don't (almost?) absorb in the frequencis of the Balmer series of atomic hydrogen emission spectrum? Thanks. -- lightarrow

The question is pretty simple really, do we have a complete knowledge on the different wavelengths of light? Or are there possibly other sources of light out there that are unknown to us?

Homework Statement The peak of the thermal radiation power spectrum (dR/dλ) is at a wacelength of about λm=hc/5kT. Why is the peak of the same power spectrum plotted as dR/df not at fm=c/λm= 5kT/h? Homework Equations dR/dλ= 2πhc2/(λ5(e(hc/λkT)-1)) f=c/λ The Attempt at a Solution

Dear Friends! We know ionized helium has two protons in its nucleus, whereas hydrogen has one. This changes the line spectrum completely. Why? Thank You in advance!

http://pdg.lbl.gov/2013/reviews/rpp2013-rev-cosmic-microwave-background.pdf Here one reads in sec. 26.2.4 that: However it states that a single Y_{lm} corresponds to angular variations of \theta \sim \pi /l. I am not getting these statements. Also I find it difficult to understand, since...