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Questions tagged [intensity]

The tag has no usage guidance.

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1answer
22 views

Affect of amplitude and distance on intensity [on hold]

A point source emits sound waves of amplitude A. The sound intensity at a distance d from the source is I. What is the sound intensity at a distance 0.5D from the source when the source emits waves of ...
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0answers
9 views

How to measure and verify ultrasound frequency and intensity from a cheap ultrasonic body contouring device?

Research shows that applying 1 MHz non-focused ultrasound at 3 W/cm2 may reduce subcutaneous fat thickness. In fact, high-end and expensive (costs $5000 >) HIFU ultrasound transducers are now being ...
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2answers
61 views

A Question About Brewster's Law

In most textbooks I read, they state that when the angle of reflection + angle of refraction = 90, there is maximum polarization. What I don't understand is what maximum polarization means. Does it ...
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1answer
31 views

A Physics Problem Involving Refraction [closed]

I'm not sure how to solve this problem. I've considered using Malus' law, but then I don't know what theta is, preventing me from solving this problem.
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3answers
68 views

What does K means in The Inverse Square Law? [closed]

Today in class i have learned the inverse square law and i was given the equation $I=K/d^2$ for some constant K. What does K really means?? I know that it is a constant but how can you get K or where?
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3answers
65 views

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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6answers
3k views

What does it mean to make a sound twice as loud? [duplicate]

Giancoli Textbook question: To make a given sound twice as loud, how should a musician change the intensity of the sound? The given answer is: "Increase the intensity by a factor of 10." I don't ...
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1answer
29 views

Wave optics, intensity distribution

Do Gaussian beams have a gaussian intensity distribution? If so, why? Does the intensity distribution depend on the profile of the light beam?
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4answers
45 views

What does the intensity profile of a set of parallel rays look like after travelling through a convex lens?

I have had a discussion at my university about the following question. Imagine a 'perfect' convex lens and a set of parallel rays, falling onto that lens. The set of incoming rays has a flat intensity ...
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1answer
29 views

Noise level x amount of meters away from an outdoor singer: sphere or semi-sphere?

When computing the noise level x amount of meters away from a singer who is singing outdoors, should one rely on the standard formula $I=\frac{P}{4πr^2}$ (and then convert 'I' into decibels) or ...
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2answers
154 views

What does “intensity of light” mean?

In this lecture from MIT, the professor defines the intensity of a wave as the square of the amplitude of the wave. But, at the same time, the professor defines the intensity of light as the number of ...
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0answers
14 views

Derivation of scattering coefficient as a function of number density of scatterers

I'm trying to derive the usual formula for intensity of light passing through scattering medium: $$I=I_0\exp(-\alpha x),$$ where $\alpha$ is the scattering coefficient (assuming it's constant), and $...
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2answers
611 views

How do polarized sunglasses reduce glare?

How do polarized sunglasses reduce intensity? When unpolarized sunlight enters our eyes through linearly polarized sunglasses the intensity is reduced. How can I understand it from the expression of ...
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1answer
549 views

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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0answers
27 views

“Intensity” as a unified term

I am seriously having trouble with the word “intensity”. Does it have different meanings when it is placed next to another word (light intensity for example) or does it always mean the same (power/...
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0answers
26 views

Energy conservation when reflecting sound from a point source

Assume I have an acoustic point source (monopole or dipole) very close to a hard wall (distance << wavelength). Following the method of images, I can represent the situation by adding an image ...
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0answers
30 views

Frequency given points of minimum intensity of a sound wave

Intensity is equal to the power per unit area. The distance between the wall and the speaker, the fact that there were three points of minimum intensity and the velocity of sound, were given, however ...
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4answers
98 views

Relationship between intensity and electron emission from a metal?

Here's the question: A xenon arc lamp is covered with an interference filter that only transmits light of 400- nm wavelength. When the transmitted light strikes a metal surface, a stream of electrons ...
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0answers
31 views

Quadratic relationship between amount of light and intensity

In a spectroscopy experiment, we were able to control the amount of light shining onto a sample by adjusting two small slits. By investigating the relationship between slit width and the intensity of ...
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1answer
34 views

Photon energy and power

My question has to do with the solar spectrum. I understand sunlight is composed of light of different wavelegnths, and these wavelegnths have different energies associated with them. I also ...
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0answers
20 views

How much information can be yanked out of an XRD Graph?

I have an XRD Graph(plotted data peaks between 2theta and intensity).I already Know the d-value corresponding to each peak.The material has an orthorhombic symmetry.What more information can I ...
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0answers
64 views

How is radiance conserved? - Power/intensity misconception

Before getting to the main question I'd like to clear some pretty basic concepts regarding energy/power/intensity as my physics is pretty rusty. According to wiki In radiometry, radiant flux or ...
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1answer
43 views

Acoustic amplitude transmission through multi layer medium

I have an acoustic wave with amplitude $A$ in ice. It passes a water-filled crevasse, and I want to calculate the impact of this passage on the magnitude of the amplitude (I do not care for the phase)...
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1answer
25 views

Fourier Transforms and bell frequency example

I am stuck on the following question: I can do the part a rather easily, but the part b i am stuck on. For now I have shown that I(Wo) = 1/(2piK^2) and 1% of this is 1/(200PiK^2) I have also ...
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0answers
47 views

Calculating total intensity of blackbody

Having trouble with this question about blackbody radiation pertaining to CMBR. Currently the distribution of background radiation is similar to the radiation of a blackbody at a temperature of 2.7 K....
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1answer
46 views

Converting illumination to irradiance

I need get intensity of an LED light source, but I cannot convert lux to $W/M^2$ How does one convert illumination to irradiance? And what is the irradiance formula?
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1answer
299 views

Intensity of electric field and electric potential [duplicate]

I know that the vector of the intensity of the electric field has the opposite direction of the gradient of the electric potential. But what baffles me is that the magnitude of the intensity and the ...
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1answer
67 views

Characteristics of light [closed]

if Monochromatic rays of some intensity fall on a metal plate placed on a rough horizontal surface at certain angle. Will the plate move if the plate is perfectly reflecting irrespective of the value ...
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2answers
47 views

Inverse Square relationship using paint problem confusion

I want to ask a question about the inverse square relationship using an aerosol paint spray mentioned in my book. I am reading the book Advanced Physics by Steve Adams, and it mentions this in the ...
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1answer
222 views

Maximum light intensity?

From what I had learned and observed, every image (light per certain area,let it be cm^2 here) can be projected onto a small or large area without any natural obstruction from intensity. So, if light ...
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0answers
18 views

Intensity vs. Spacing Graphs

Fig. A is an intensity pattern seen behind a double slit. While Fig. b is an intensity pattern seen behind a single slit. Based on what is given, am I safe to assume that the maximum for Fig. A is (...
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2answers
534 views

How does distance affect light intensity? [closed]

Why does light intensity decrease as the distance increases from the light source?
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3answers
606 views

Why do we use decibels instead of just using intensity to measure how loud things are?

In my physics book, it says that in the human ear, the sensation of loudness is approximately logarithmic. And that the relative sound intensity is directly proportional to a logarithmic ratio ...
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0answers
54 views

What is the inverse notion of Intensity?

What would be the inverse notion of intensity? What would be the inverse of a level of effort per unit of something? Say that we deal with the intensity of sunlight at the surface of the earth, in kW/...
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1answer
959 views

Compton Effect (graph between relative intensity and wavelength)

Why is the peak of the graph more for greater wavelengths? Since wavelength is inversely proportional to energy and relative intensity, shouldn't the peak for greater wavelength be lesser? Please ...
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1answer
159 views

Inverse square law - brightness and distance [closed]

I am working on a lab report wherein I am given a bunch of readouts from an experiment that measures the brightness (lux) of light at set distances (cm). When I apply the inverse square law, $$\frac{...
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1answer
952 views

What happens to the diffraction pattern when the width of a single slit is increased?

https://phet.colorado.edu/en/simulation/wave-interference According to the simulation in the above link if the width of the slit is sufficiently increased then the intensity of the central point ...
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0answers
174 views

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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2answers
8k views

Exact relationship between electric field and intensity

I often see $I(t)\propto |E(t)|^2$. What is the exact form ? Which constants are missing to make this an equality and why are they so often omitted ?
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1answer
823 views

Factors on which brightness of light depends

Does brightness of light depend on number of quanta in the light? It makes sense assuming that the number of photons would affect the brightness of light.
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1answer
165 views

Intensity of superimposed waves at the michelson inferometer

The Problem is about the Michelson Inferometer described by the picture below Let the Beam Splitter be one, who reflects half of the intensity and transmits the other half of it. Furthermore assume ...
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1answer
168 views

Meaning of “intensity” in the optical Kerr effect in optical quantum computation

Kerr media, or mediums displaying the optical Kerr effect, are used in some optical quantum computers - on Chuang and Nielsen's Quantum Computing and Quantum Information, pgs. 289 - 290, it says, ...
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1answer
113 views

Intensity at $\theta = 0$ in slit diffraction

From the explanation on diffraction at http://web.mit.edu/viz/EM/visualizations/coursenotes/modules/guide14.pdf $$I = I_0\left [ \frac{\sin(\beta/2)}{\beta/2} \right ]^2=I_0\left [ \frac{\sin(\pi a \...
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1answer
133 views

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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0answers
42 views

Light wavelengths and intensity at 10 m depth in coastal water

I’m planning an experiment in tanks under controlled conditions in which we’ll collect marine animals and observe their behaviours. We want to replicate to the best the light that they receive under ...
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2answers
402 views

Light Intensity vs Visibility/Brightness?

I am curious about something that doesn't seem to be pointed out very much. This is the double-slit intensity pattern as a graph: This is what you're supposed to see in real-life: If you look at ...
3
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2answers
170 views

Are there experiments that deal with the headlight effect?

If I am not mistaken, the Ives-Stilwell experiment measures the frequency of emitted light to test the relativistic doppler formula. Is there anything like this for light intensity? Have we measured ...
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1answer
412 views

Does a circular surface water wave decrease by 2$\pi$r?

Does the energy of a wave in water decrease by (2$\pi$)r? If that is right, why do we see waves at a considerable distance of almost same intensity of the near ones?
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1answer
31 views

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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1answer
99 views

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 ...