# Questions tagged [attenuation]

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### Determining the photon beam intensity to confirm the placment of an object in a iradiated chamber [closed]

A parallel bundle of monoenergetic photons is used for imaging in the configuration below. The bundle passes through a layer of water with a thickness of 1 cm, then through a zone where a cube with a ...
529 views

### Getting the spectrum of light source at high intensity (for low transmittance measurement)

I am trying to measure the transmittance spectrum through a liquid sample using a visible-NIR spectroscopy (a spectrometer connected to a fiber optics and a collimating lens at the end), with tungsten-...
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### Calculation of Ultrasonic Attenuation Coefficient

Hello I have a conceptual question regarding calculating the ultrasonic attenuation coefficient for a transmitted wave within a solid material. I have seen Beer's Law used to calculate the attenuation ...
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1 vote
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### Beer's Law ultrasound attenuation, account for spherical spreading?

I've seen Beer's Law for narrow beam written as: $$I = I_0 \cdot e^{-\alpha x}$$ ${\alpha }$ - attenuation coefficient (depends on absorption and scattering), $I_0$ - initial intensity, $I$ - ...
24 views

### How can we describe the attenuation of sound in an expanding gas cloud in a vacuum?

For example, suppose a spaceship explodes. The sound of the explosion will travel in the expanding cloud of escaping gas. I gather that it should rapidly weaken and the pitch should drop, but I'd like ...
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### Does EM wave lose energy in air?

Light is EM wave. As it travels through vacuum, it does not lose energy but I am wondering if it travels in air, just imagine light in your home. Before it reaches your eye, it has to travel through ...
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### What is the formula for the power of a laser at distance $x$ (taking attenutation into account)?

While this is inspired by science fiction, if I have a hypothetical laser weapon that needs to meet a very high energy requirement of energies of the order $1 \times 10^{22}$ Joules, what formula ...
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### Why does audio signal amplitude always fall off at higher frequencies?

In the frequency spectrum of every real audio sample that I've ever seen, the amplitude of the frequency components is always higher at low frequencies, then rapidly falls off at higher frequencies. ...
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### How do you calculate light attenuation by wavelength at a given air mass coefficient?

I am trying to get a good view of light wavelength distribution as a function of viewing angle, with a specific interest as $z \approx 90^\circ$ near the horizon (sunrise/sunset). Air mass ...
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### The impact of electron density on photoelectric effect

I'm a second year radtion therapy student and i'm looking at the attentuation of KV energy beams. I'm wondering why for the photoelectric effect to occur does there need to be a high amount of 'inner'/...
40 views

### How does wavelength affect scattering?

Let's say that I have a detector and a few sources of light (think lightbulbs). The sources are all the same power and emit different colours of light. We're on the surface of Earth. As I walk further ...
89 views

### Effective optical depth using Beer-Lambert law for non-linear attenuation?

Currently I have a gas with a density that follows and inverse square law in distance, $r$. Given that I know the mass attenuation coefficient of this gas, I wish to calculate an effective optical ...
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### What is the maximum distance that music is transmitted through the air?

I would like to hear your advice on which method to use to transmit music or speech in a frequency band that is sensitive to the human ear up to 3km. Everyone knows that the higher the frequency, the ...
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### Collisional cross-section from attenuation factor

I am trying to find the mean free path of silver atoms travelling through air (I am given the temperature, pressure and that they are attenuated by a factor $2.72$ in a distance of $10^{-2}$m). I know ...
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### Does the inverse square law of sound change with frequency?

High frequency For example, I try to chase wild animals by creating a high sound pressure level with a frequency of 17 kHz or higher, but I can't calculate the initial sound pressure. One thing is ...
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### Calculating the absorption length of attenuation?

The flux of neutrons is attenuated according to the formula: $$F = F_0 e^{-Ax}$$ And I want to find from the absorption length, defined as the length at which oncoming neutrons is reduced by a factor ...
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### 3D Point Source Attenuation Equation

I was given the following equation to measure the intensity of a point source where $r_o$ is the reference and $r$ is the distance away. I do not understand what to do if I make the coordinate origin ...
354 views

### How does x-ray attenuation compare to sound wave attenuation?

When it comes to medical imaging (x-ray and ultrasound specifically) there seems to be a difference between the attenuation of sound and x-rays. What I am gathering is as follows: When it comes to x-...
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### Is it possible to take long-distance X-ray images at a high resolution in Earth's atmosphere?

It's my understanding that different wavelengths of EM radiation are affected by scattering and attenuation to varying degrees. Would a camera using only X-rays be able to take a picture of something ...
55 views

### Why are daylighting fibre optics so much more inefficient than other fibre optic cables?

Comparing Optical Fiber Light Tubes losses and regular Fiber Optic Losses, there seems to be a large disparity. The light tubes reach 100m, whereas the regular ones go for kilometers. I've tried to ...
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### Can light transmission through mostly opaque but radio-transparent materials be increased by amplitude modulation?

Can a laser modulated at a low frequency (microwave or radio frequency range) be transmitted further through a medium because the laser is modulated at an envelope frequency that the material is more ...
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### Solar panel voltage reducing by adding cellophane

For a physics report, I am aiming to answer the question How does the power output of a solar cell vary with the thickness of cling wrap laid over it? I got a negative relationship between voltage and ...
1 vote
134 views

### What is the difference between areal density and attenuation coefficient?

Speaking of beta electrons, their attenuation is usually described by the areal density $\sigma$, i.e. "how much" g/cm^2 of a certain material they can pass through before stopping. I've ...
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### Conductivity and loss in electromagnetic waves

I have learned electromagnetic waves in a free space (conductiviy=0) propogates without loss. But if medium have conductivity there are 2 cases good insilator case and good conductor case. In a good ...
10 views

### Crystals thermal neutrons can pass throw without significant change in their energy

I looked online for a really long time already for crystals which thermal neutrons can pass throw without significant change in their energy. Does anyone here know which crystals have the minimum ...
2k views

### How far can an x-ray travel through water?

I am studying x-ray's and how they interact with different mediums, but I am a bit confused on the distances an x-ray can travel through different mediums such as water. Let's take an x-ray with 3 ...
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### Attenuation of a signal

Suppose that I have a wire between two terminals and I want to send a high frequency ($f$) signal from one to another. Is the inductance and capacitance per unit of distance enough to calculate the ...
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### How to determine at what point regeneration of a signal is necessary?

I have a "homework" question that has raised some doubts in my mind about when regeneration of a signal is necessary and whether it can be determined from a given SNR (signal to noise ratio) alone or ...
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### Can a wind turbine be audible at 3.5 kilometres?

Here is the link to the research supposedly claiming that wind turbines can be heard 3.5 kilometres away inside a house 16% to 22% of the time. The article further claims on occasions audible noise ...
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### What form(s) of radiation are least attenuated by the atmosphere?

Given the composition of Earth's atmosphere, what is the most efficient way of wirelessly beaming energy from the stratosphere down to the surface?
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### Are absorption and attenuation the same thing?

Are absorption and attenuation different words for the same thing? Wikipedia separate has articles on Absorption (Acoustics) and Accoustic Attenuation. I don't see a clear physical distinction between ...
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1 vote
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### Is the sound of hammering nails louder since it travels through the walls?

The question might sound silly but hear me out. When people are hammering nails into a wall in a nearby room, you can often hear it very loudly. It seems natural to suspect that this is because, on ...
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1 vote
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### Conversion formula between attenuation coefficient (cm^-1) and (dBcm^-1MHz^-1)

So, I was presented in class the fact that (at least in Ultrasound), attenuation coefficients $\mu$ can be expressed in units $\text{dBcm}^{-1}\text{MHz}^{-1}$ as opposed to the form I was used to; ...
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### Why is sound attenuation greater in dry air than humid air?

I have just learned the surprising fact that the attenuation coefficient of sound in air depends strongly on relative humidity: at any given frequency, it can be several times larger in very dry air (...
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### As a sound burst attenuates does it get longer?

I am trying to understand what a sound burst will look like after frequency dependent attenuation. I come from engineering / signal processing not physics background. If I am told as an engineer to ...
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### Do photons attenuate when they reflect?

I was watching a video on solar sails and it described how the momentum of the individual photons striking the sail is planck's constant divided by the wavelength of the photon. Does this mean that ...
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1 vote
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### How can the loss of light irradiance due to both attenuation and the inverse square law be modelled?

When considering the effect of depth on just light attenuation (is within an aqueous solution), the Beer-Lambert law is used. From what I've found, the law is derived by determining the fractional ...
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1 vote
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### Why does sound attenuate in air differently in different situations?

Sound attenuates in air, and some frequencies go quieter quicker than others. But it feels like which frequencies get quieter should be consistent. Here's two opposing examples: At a party, there's ...
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### Is the radio attenuation of an obstructed 2.4GHz signal, dependent on its incident power?

The following figure (taken from CTS 115: Free Space Path Loss) describes generally how obstructions attenuate a 2.4GHz signal: I would like to ask, is this -3dB loss dependent on the power (or ...
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Having a look at https://www.nist.gov/pml/x-ray-mass-attenuation-coefficients, the introduction states: For compounds and mixtures, values for $μ/ρ$ can be obtained by simple additivity, i.e., ...