Questions tagged [intensity]
The intensity tag has no usage guidance.
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Difference between steady state intensity and saturation intensity in laser
Can someone explain the difference between steady state intensity and saturation intensity in lasers? And difference between gain at threshold and gain at steady state, why are these two gain equal?
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Why is stopping potential independent of frequency of photoelectron?
All the books and internet articles I have read so far claimed that the stopping potential and the maximum kinetic energy attained by a photoelectron is independent of the intensity with which the ...
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How to Calculate the Spectral Intensity per Solid Angle in a Tungsten Bulb - Photodetector Setup
I have a setup with a tungsten bulb. The bulb has a 2cm diameter aperture in front of it. When the bulb is turned on, light from it hits a bi-convex lens 21.5cm away which then focuses the light onto ...
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Energy conservation in the combination of two coherent beams
I was asked a question today by a student that I couldn't find a satisfactory answer to.
Imagine we have two identical laser beams with average electric field strength $E$. Upon combining these beams ...
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How do we calculate the irradience of an EM wave?
I've been told that the Irradience = time average of the electric field squared. However, I've also been told that it's equal to the total Amplitude of the electric field squared. I'm kinda confused ...
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What determines how much power goes into each diffraction order?
Imagine a grating with infinite number of slits, and the spacing D between slits is larger than the wavelength so that there are high order diffractions. In each of the diffraction directions the ...
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Does the number of photoelectrons depend on the area of the beam for a given beam power?
I don't understand something in the photoelectric effect experiment (which consists in shining light to a metallic material and then measuring the kinetic energy of the ejected electrons, as well as ...
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Does intensity of sound depend on temperature or humidity?
The intensity of sound $I$ can be written as $$ I = 2 \rho v (af \pi)^2$$
I googled and found that increase or decrease of temperature doesn't have any impact on sound intensity. But why is that? ...
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Electric field/intensity for complex envelope
When calculating the propagation of a pulse I can either use an envelope-based or a carrier-based approach. For the carrier-based approach I can define my (focused) pulse with the central frequency $\...
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Is the intensity of light dependent on number of photons per unit area?
I was learning about the photoelectric effect of light and there it says more the intensity of light, the more number of electrons will be ejected from the metal surface given that the frequency of ...
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Sunlight intensity, temperature and lens flare
1- How can I calculate the sunlight intensity in percentage? (without external influences such as clouds or pollution).
In this site SunCalc, Solar constant changes from location to site or from time ...
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Confusion about sound intensity
I think there is something fundamental I'm not understanding about sound intensity.
I have a small speaker at home, roughly 10cm square and the specs state it has 3 W output. That equates to 300 W/m^2 ...
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What does the Interferogram of a FTIR-spectrometer show ? Is it instantenous intensity vs time or time averaged intensity vs time?
I try to get a clear understanding of FTIR spectroscopy and it is unclear to me what exactly the interferogram shows. I know that we see the intensity of the superpositioned beams where we vary the ...
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Doubling up on Ear Protection NRR Equation
I'm planning to go to shooting ranges soon, and am looking for ear protection.
Let's say that I get an earmuff with a noise rating reduction (NRR) of $X\ \textrm{dB}$ and earplugs with $Y\ \textrm{dB}$...
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How to calculate the intensity of a light when using the ray model?
Suppose that there is a point light source with power $P$. We are interested in a single light ray visualised in the above picture. The ray travels a distance $r_1$ and encounters a surface. The ray ...
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Derivation of the formula for intensity of sound wave [duplicate]
I was trying to derive the formula for finding the intensity of the sound wave, after deriving it in my way i am missing a factor of 2 in the formula, Can I know what I am doing wrong ?
Here is my ...
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Intensity of light - questions about the particle standard definition and concerning the units [duplicate]
In the $5.111$ MIT class, lecture $3$, it is written on the last slide "intensity of light = photons per second". Intensity is previously defined in the lecture as the square of the ...
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Why is the intensity of a beam of light the squared magnitude of the phasor and not just the squared magnitude of the real part?
I'm learning about phasors and light intensity and there are two conflicting things I've been told that I can't reconcile.
Firstly I've been told that a phasor $e^{-ikz+i\phi}$ is a mathematical way ...
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Demonstration of constant radiance for Lambertian Surfaces
I'm approaching to radiometry and I'm struggling with one of the properties of Lambertian surfaces.
We know that the radiance is the radiant flux emitted, reflected, transmitted or received by a ...
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Why is intensity additive?
In class we came across a problem that is essentially the following:
Suppose a source of sound has an intensity of 70 dB. Suppose 9 additional sources produce the same sound in unison (so 10 ...
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Question about Proportionality in Sound Equation (Pressure and Displacement Amplitude)
Why is intensity in terms of pressure amplitude inversely proportional to density and velocity:
$I=\frac{\Delta p_\text{max}^2}{2\rho v}$,
while in terms of displacement amplitude, it is proportional ...
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Converting laser irradiance into volume energy density
If I want to convert a laser's irradiance of $10^{20} \,\text{W}/\text{cm}^2$ into a volume energy density, do I just divide it by the speed of light $c$?
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Intensity of Light in a 2D Flatland?
Given the figure below, it specifies that the intensity of light at a given distance is:
intensity = 1 / d^2
After working on an implementation for Radiance ...
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If a star's luminosity doubles, does its received flux double?
If the luminosity of a star increases or decreases in some way, would the received flux increase or decrease by the same amount (linearly) or would it change by the square of the luminosity (inverse ...
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Confusion between two equations for sound intensity
The definition of sound intensity is $I=P/S$, where $P$ is the power generated by the wave source and $S$ is the area over which the energy is transferred. Assuming conservation of mechanical energy ...
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Modeling an Electrolyzer System
In this study, the authors provide an equation for operating cell voltage: $V_{cell} = V_{rev} + V_{act} + V_{ohm}$, the sum of the reversible overvoltage, the activation overvoltage and the ohmic ...
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Inverse Square vs Exponential
I feel a little foolish asking this, but I keep reading sources which say that for an inverse square law relationship, e.g. light intensity vs distance from source, the intensity decays exponentially.
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Doubt in the definition of intensity
So I know that radiant intensity is defined as "power transferred per unit solid angle per unit area which is perpendicular to the direction of propagation of energy". So now I have a very ...
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Relation between intensity of light and amplitude of electric field?
A question in my textbook involve finding the electric field amplitude at a point in space given the intensity of light. It uses the following equation to solve it:
$$I=\frac{1}{2}\epsilon_{0}|E|^2c$$
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How HBT interferometery works?
I am still confused about how HBT interferometry for star angular size works after reading about it on the internet and in papers. Mathematics usually does not help before I do not catch the way the ...
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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 ...
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Convert $\rm Lux$ to $\rm W/m^2$
I use four LED matrix (UV, green, red, blue) to irradiate a solar panel with an area of S at a distance. The matrix is located at a distance l from the solar panel. I want to plot the volt-ampere ...
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Calculating in-duct sound intensities from sound pressure measurements with mean mass flow
In the time domain and in free field condition the sound intensity can be calculated as $ \vec I(t)=p(t) \cdot \vec v(t)$ with $p(t)$ being the sound pressure and $\vec v(t)$ being the sound velocity. ...
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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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Why sound gets weaker as it travels in air? [closed]
When we talk, our vibrating chords oscilate next air molecules which oscilate the next molecules and so on. Hence sound wave travels.
As we know, energy that reaches the destination is not the same ...
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Why we typically see no deeper into an atmosphere for an optical depth of 1?
In An Introduction to Modern Astrophysics (p.243), Carroll and Ostlie say that for a optical depth $\tau = 1$ the intensity will decline by a faction of $e^{-1}$.
$I_\lambda = I_{\lambda,0}e^{-\tau}$
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Is the intensity of light ONLY dependent on the number of photons, and nothing else?
Recently, my teacher just told us that intensity is not linearly dependent on temperature and that it's ONLY dependent on photons. But then, what about Boltzmann's law? Isn't intensity dependent on ...
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Derivation of intensity of a sound wave (missing calculation in the book)
The question is about a calculation in the first section of this page: https://openstax.org/books/university-physics-volume-1/pages/17-3-sound-intensity
Essentially, it states: "To find the time-...
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What is the relation between reflectance and intensity?
I am just reviewing Fresnel's equations where Reflectance $R$ is equal to
$$R=|r|^2$$
where $r$ is the complex reflection coefficient. Is there an equation that relates $R$ to intensity or is there ...
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Intensity of light and energy at a photonic level
If I understand correctly, the intensity of light is proportional to the number of photons hitting a certain area.
If we then look at a single photon when described as a transverse wave, is its own ...
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Can we say that amplitude of light scattered by air molecules is inversely proportional to the square of wavelength of incident light?
As per Rayleigh's criteria of scattering of light by air molecules the intensity of scattered light is inversely proportional to the forth power of wavelength.
AND WE ALSO SAY :
Intensity of a wave ...
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What is $dE/dR$ and how does when $dE/dR=0$ makes electrical field intensity maximum? [closed]
Actually my question is that when $dE/dr=0$ then $dE$ also comes out to be zero then how does electric field intensity maximum when $dE/dr=0$. And also I don't understand that how does this value came ...
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Intensity of central maximum for a diffraction grating
If I send a typical 5 mW, 532 nm laser pointer beam through a diffraction grating (~1,000 slits/mm), then I'd expect the beam to cover something like ~1,000 slits. The resulting intensity of the ...
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Calculating measured intensity of a Gaussian beam
Consider a light source which emits a Gaussian beam with total power $P_0$, initial width $d$, and divergence half-angle $\theta$ (in radians). The beam radius, measured from the waist of the beam, ...
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Why doesn't the Intensity of laser light drop by $\frac{1}{r^{2}}$?
If we observe a laser we see its intensity wont drop by $\frac{1}{r^{2}}$ as seen for regular light sources as its very concentrated and even remain somewhat same for long distances (even though its ...
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Is the intensity of a light wave related to frequency of the wave?
My problem is: How can I resolve these following ideas?
Energy of photons in an EM wave is proportional to the frequency of the wave
Intensity of an EM wave is proportional to the energy that is ...
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Would different sounds of the same intensity but different frequencies have the same harmful effect on the human ear?
The "safe noise exposure limits" I found on the internet only indicates the intensity of the sound in dB, but not the frequency. Does that mean that e.g. a 120dB sound with different ...
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Why does an increase in my sound intensity lead to an increase in frequency range?
I am a biologist studying frogs, and as part of my research I use hundreds of thousands of audio recordings (.wav) from autonomous recording units. I use various software to create recognizers that ...
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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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Are the intensities of waves equal when they are represented in real vs complex notation?
The intensities should be equal no matter how a wave is represented. So clearly I think i'm making some elementary mistake, it seems they are not same :
$$
\Phi(x,t) = A_0 \cos{(kx-wt)} \\ \Phi(x,t) = ...
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