Questions tagged [intensity]
The intensity tag has no usage guidance.
201 questions
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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 :
$$
\Phi(x,t) = A_0 \cos{(kx-wt)} \\ \Phi(x,t) = ...
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Defining the loudness in terms of mass and time
The unit of loudness is $$\rm\frac{W}{m^2},$$ which is equivalent to $$\rm\frac{kg}{s^3}.$$ Since kg is the SI unit for mass and s is the SI unit for time, this led me to the following question:
Can ...
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Effect of thickening polariser on intensity pattern
I've performed an experiment where microwaves were sent through a polariser of varying thickness, composed of $11$ slits (width and spacing both $6$ mm).
To vary the thickness of the polariser, this ...
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How does the intensity of light in a double slit experiment vary with the slit width?
I know this question has been asked quite a few times on the network but I still can't find a concrete answer. It's quite clear that intensity depends on the square of slit width in a single slit ...
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Why would there be a larger data dispersion at minimums than at maximums in a graph of intensity against path difference?
I'm doing a rather simple experiment concerning the superposition of two waves and the impact that path difference of 2 identical waves has on recorded intensity at that point. However, there is ...
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Derivation of the exoplanetary flux observed at Earth (solid angle problem)
I'm having issues understanding how Sara Seager, in her book "Exoplanet Atmospheres", determines the solid angle subjected to a detector on Earth. By the figure:
The solid angle was defined ...
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If $I$ is the intensity of the principal maximum in the single slit diffraction pattern, then what will be its intensity if the slit width is doubled?
I've found a few results on the internet for this question, all with different explanations or different answers. Some say it'll become 4I and some that it'll not change. I see that there are a few ...
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Decibels, acoustic intensity and sound perception
I know the formula: $I[dB] = log_{10}\left(\frac{I}{I_0}\right)$ with $I$ being the acoustic intensity in $[W/m^2]$ and $I_0 = 10^{-12} [W/m^2]$ being the human threshold of hearing. Also, I am told ...
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Deriving the Interference Intensity of Michelson interferometer
I am trying to equate the equation i found wikipedia:
To the one given in my course notes which is:
Assuming a 50/50 beam split i have 1/2 where i should not have one:
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Question about unit for intensity
The picture is from one physics textbook about treating sun as a blackbody and compare the electromagnetic radiation spectrum. Note the unit used for Intensity in the picture shown, it's Watts / (...
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Why a wave whose intensity is modulated sinusoidally have different frequency compared to original wave even though intensity depends on amplitude?
While experimenting to find the velocity of light, instead of finding the velocity of light, we used the light wave whose intensity was varied sinusoidally and found the velocity of light using the ...
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Intensity Poynting
Take a plane wave propagating in the $\hat{z}$ direction in a non-magnetic linear dielectric. The real electric field is then given by
$$\vec{E}(r,t) = E_0\, e^{-k_i z}\cos(k_R - \omega t)\, \hat{x} ...
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How was the black body intensity vs wavelength (or frequency) radiation curve historically produced?
I have read that Wilhelm Wien gave his formula to match the radiation curve of a black body as shown in the picture; which works well in high frequency region. Another formula by Rayleigh-Jeans is ...
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Sound Relationships
Whats the relationship between amplitude, volume, and wave energy. I have tried many websites but none have helped me yet and I believe maybe someone on here can help me.
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Sound waves adding up [duplicate]
If there is a swarm of bees, why is it louder than a single bee? This question may sound stupid but ... if they are all buzzing at the same frequency with the same loudness and the phases of the sound ...
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If the range of a laser depends on its crossection perimeter does it mean that a wider beam would reach much longer distances?
If the range of a laser depends on its crossection perimeter does it mean that a wider beam would reach much longer distances? Let pressume that we can construct a 1m wide laser beam and as we know ...
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Acceleration due to incident radiation on plate
I have tried the following question and getting a wrong answer.
Monochromatic light of intensity I falls over a blackened plate of area A, at an angle $\theta$ as shown in the figure. If 70% of light ...
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Why we have used 20 log to convert magnitude into db instead of 10 log?
We know that,
$$db = 10 \log P$$
$$=> db = 10 \log X ^2$$
$$=> db = 2*10 \log X$$
$$=> db = 20 \log X$$
Now, my question is, why we use $20 \log$ for converting magnitude into db instead of ...
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What is the displacement amplitude of a 140 db sound wave?
I am teaching a unit on sound in my upper elementary science class, and my students are curious about how far air molecules are actually being displaced in a sound wave. I told them that if the air ...
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Does, and if so, why does the frequency of light and wavelength of light affect the photoelectric current?
It makes sense that intensity of light affects the photoelectric current, but what about the frequency and wavelength, given that intensity remains constant?
The formula for intensity would be I = nhf/...
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What is the formula for the intensity of light, and how are amplitude, frequency and number of photons considered?
One formula for light intensity is$$
I = \frac{nfh}{At}
\,,$$where:
$n$ is the number of photons;
$h$ is Planck's constant;
$f$ is the frequency;
$A$ is the incident area;
$t$ is time.
Another ...
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What is the difference between Luminous intensity and intensity of illumination?
What is the difference between the Luminous intensity and intensity of illumination? Please explain with units and dimensions as well! I googled but I partially understood it!
CommunityBot
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How to use Malus's law to get real output energy from a polarizer?
As we know, the Malus's law is:
$$I=I_0\cos^2\theta.$$
Presently, I have a polarizer system (one half wave plate in front of a polarizer) in the lab, and have a powermeter. So, I can get two key ...
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Why the intensity of a wave is $ \Psi \Psi^*$?
In here at the bottom, it says the intensity of a wave is the wave phasor times it's conjucate
$$ I(x) = \Psi \Psi^* = |\Psi |^2$$
But when I compute the intensity of an electromagnetic wave in c.g.s, ...
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How does the spot size of light change the photocurrent?
I want to understand the photo electric effect. If I shine light at a surface then a photon can knock an electron off the surface if its energy $h\nu$ is larger than some minimum material specific ...
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I have seen people define frequency or amplitude in two ways, which one is correct?
I have a doubt on frequency and amplitude,I have seen people define these things in 2 ways,for instance, people define frequency in mainly 2 ways,if we draw a pressure-position graph of a sound wave,...
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Why solar flux concentrators can achive only $\rm 1500°C$ of temperature if Sun temperature is $\rm 5500°C$?
Why solar flux concentrators can achive only $\rm 1500°C$ of temperature if sun temperature is $\rm 5500°C$ ? If it is possible to concentrate a flux from a parabolic mirror of area $\rm 400\ m^2$ to ...
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Sound, additive principle or not? How to prove?
If we have $N$ sound sources with $L_1, L_2,...$ with intensities $I_1, I_2,...$. How to prove that
$I_{total}= I_1 + I_2 + ... $ but $L_{total}$ is NOT $L_1 + L_2 + ... $
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Is there a way to calculate the intensity of light absorbed that passed through a solid?
So I have lab I need to do for school and I need a formula that calculates the intensity of light transmitted through a solid (in my case sheets of paper). I had a probe that measured the intensity of ...
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Law of amount of interference between different Sun rays that fall on a distinct point on Earth?
The double slit experiment shows that rays comming from different locations can cancel each other when touching a point on a screen if they are out of fase because of their wave properties. Is the ...
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Intensity of light transmitted by a polarizer when the incident light is unpolarized
my question is similar to this older one, but I have not enough privileges to answer it or comment on it.
I do realize that the question has received detailed answers by Selene Routley, and I sort of ...
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How does intensity depend on slit-width regarding Fraunhofer diffraction?
For a single slit, considered to be infinitely long, with size $b$ the intensity at any angle is given by:
\begin{equation}
I(\theta)=I(0) \bigg( \frac{\sin \beta}{\beta} \bigg)^2
\end{equation}
...
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How is energy in terms of Intensity and Amplitude comparable to Energy in terms of Frequency?
Let's take LASER light. It has a high energy ,in terms of Amplitude, let's take a red light, of same frequency ,we are giving each of these to two atoms , now atom no $1$ is subjected to LASER light ,...
CommunityBot
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Mathematical Derivation of Expression for the Total Power Received By Earth from Sun, via Integration [closed]
I recently tried to derive an expression for the total power received by the earth from the sun, using integration. However, I am stuck at an integration step. Would appreciate if anyone could help ...
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Cauchy-Schwarz inequality in terms of intensity measurements
Hi I was reading Introductory Quantum Optics by Gerry and Knight, particularly the part about higher degrees of coherence (Section 5.4), and in there they write:
Now according to Cauchy’s inequality ...
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Unequal arm length Michelson Interferometer Light Intensity
Imagine a Michelson interferometer with unequal arm length. A laser beam with an electric field of the form $$E(t,z) = 2E\cos(ωt+kz)$$ is incident on a 50/50 beam-splitter. The first arm is of length <...
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Wine color vs. quantity
Looking down at red wine in a glass, if the quantity of wine is doubled, the color darkens. Is there an equation that describes how the color changes as the quantity of wine is increased?
Is it ...
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Electron emission and photoelectric effect affected by intensity
It is said that when visible light is directed onto a metal surface, it doesn't emit electrons from the surface because intensity doesn't affect it. However, then it is said (relating to the equation) ...
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Will I be able to see a light coming from a laser in the edge of the universe?
It is said that light's intensity decreases with increase in distance. Suppose if there is a laser in complete vacuum, emitting a collimated light beam from one end of the universe for about 93 ...
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Poynting vector and intensity of a signal
Given a plane monochromatic electromagnetic wave propagating in $x$ direction, with associated electric and magnetic fields of the form:
$\overrightarrow{E}(x,t)=\overrightarrow{E_0}\cos(kx-\omega t), ...
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Photoelectric effect with high frequency and low intensity of light [closed]
What happens to the number of photons striking the free electrons on metal surface with high frequency and low intensity of light? High and low intensity of light of photons to electron on metal ...
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Photon irradiance and solid angles
A blackbody is in equilibrium with a radiation field at $\nu$ when
$$
I(\nu)=\frac{8 \pi \nu^{2} }{ c^{2}}\left(\frac{1}{e^{h \nu / k T}-1}\right)
$$
where $T$ is the temperature of the blackbody and $...
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Does emission of electron depend on colour instead of brightness of light?
According to photoelectric effect we consider light to be particles to justify the threshold wavelength in light.
It says that the energy of electron emitted depends on wavelength of light that falls ...
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Confused on intensity of light
If light behaves both as particle and wave at the same time, does it mean intensity (energy) of light depends on the square of its amplitude and at the same time energy of photons doesn't depend on ...
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Electric field intensity $E$
Electric field intensity (E) is defined as the electrostatic force experienced by a unit positive charge , mathematically E = F/q,it seems like the mathematical equation E = F/q contradicts the ...
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Why is acoustic intensity inversely proportional to density of the medium?
The definition of sound (acoustic) intensity is given by
$$ I = {p^2 \over {\rho c}} \;\;\;\; \text{or} \;\;\;\; I = {p^2 \over {2\rho c}}$$
I've seen both definitions in different textbooks and am ...
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Why do we add intensity instead of pressure for sound waves? [duplicate]
If two sound sources cause sound levels of 50dB and 53dB independently at a certain point, to measure the sound level at that point we have to first convert each sound level (dB) to its intensity ($ W/...
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Relation between Displacement Amplitude and Intensity of Sound Waves
How do we derive a relation between the displacement amplitude and the intensity of a sound wave? I saw a formula on the internet regarding the same i.e
But I can't find a way that would help me in ...
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How to calculate charge density [closed]
I am trying to solve this exercise:
Using this formula calculate electric intensity
$$
\vec{E} = \frac{\vec{c}\times \vec{r}}{r^4}
$$
$\vec{c}$ is constant vector, $r$ is magnitude of the position ...
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Relationship between intensity and sound level
So I know that for every tenfold increase in intensity, the sound level increases by 10 dB. So if the intensity is increased by a factor of 100000, the sound level increases by 50 dB. I also know that ...
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