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Questions tagged [intensity]

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Quantum description of intensity measurement

The traditional way to formulate the measurement of the intensity in an optical field is by using the number operator $$\hat{n} = a^{\dagger} a .$$ In effect one can say that the intensity, which is ...
7 views

Calculating intensity from Debye formula for Iron

Following is the question I am trying to answer: and this is what I have done so far: Any idea how I can progress from here? I think plotting a graph of intensity against |K| or 2*theta is the way ...
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What does 'per unit frequency' refer to?

We were discussing Kirchoff's theorem on blackbody radiation in class today and the equation was: $$e_{f}= J(f,T)$$ $e_f$ was defined as power per unit area per unit frequency. What does per unit ...
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The meaning of the area in the intensity equation $I = P/A$

I am a bit confused on what the area A means in the equation for intensity. I know that the area here uses the surface area of the sphere equation and the book I use says that A is the area of the ...
54 views

Electric Field Intensity

The electric field intensity everywhere is $E=E_0-j$ (y-direction) in vacuum (say $E_0=5$). if you have an infinite-perfect conductor starting at the $x \geq 4$ plane and $x < 4$ is vacuum. What ...
6k views

How strong are Wi-Fi signals?

My family members dislike the idea of having many devices communicating wirelessly in our house, arguing that the signals have negative effects on our physical health. I would like to tell them the ...
39 views

Power and intensity of a sound wave

So in the case of a point source of a sound wave in a sphere, I'm wondering why the Intensity decreases with $r^2$ because if i setup the formula the Power always increases with $r^2$. So these two ...
18 views

Is this the correct interpretation of specific intensity?

I've always been taught to define specific intensity as the following quantity: if I have a detector here next to me with an area element $dA$ and I detect a power element $dP$ from a source of solid ...
42 views

Brightness of colors

I have 1W lights, red and green. If I turn the red light full power I get 1W red light, if I turn green light full power, I get 1W green. If I want to mix the lights and get yellow light, which has ...
51 views

Are / Why are the H II regions positively charged?

One of the questions in our recent astrophysics course homework was to find the general opacity $\kappa$ of H II regions. We know that the H II regions are almost entirely ionized hydrogen and I ...
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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 ...
158 views

How is energy conserved during simultaneous refraction and reflection of light?

My question is regarding the partial reflection and refraction of light when incident on a refracting surface. Here, the energy of Incident Ray is E=hv of Reflected Ray is E=hv and that of Refracted ...
96 views

Photoelectric Current [duplicate]

Recently learnt that Intensity= nhv ; where n is the number of photos per unit area My textbook specifies that the photoelectric current only depends upon the number of photons striking per unit time ...
94 views

why does the intensity of light does not vary with time in youngs double slit experiment

[ we can see that resultant electric field at a point p is given $E=E0\sin(kx-\omega t+\epsilon)$[equation highlighed with yellow color] as the resultant field varies with time, why not ...
71 views

Calculating light intensity with Fresnel's Equations [closed]

When light gets reflected or transmitted by another medium it's intensity splits for both the parallel and perpendicular component. Using Fresnel's equations calculating the reflected intensity which ...
315 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 ...
37 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.
356 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?
171 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 ...
4k 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 ...
98 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?
96 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 ...
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 ...
907 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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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 ...
73 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 ...
60 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 ...
445 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 ...
1k views

How does distance affect light intensity? [closed]

Why does light intensity decrease as the distance increases from the light source?