# Questions tagged [intensity]

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1answer
202 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 ...
0answers
28 views

### Below what threshold of intensity can a ray of light be considered absorbed?

Say I have a beam of light of intensity I. I'm modeling its traversal through a medium which absorbs light. As it travels, I reduce its strength by a certain specified factor. Below what intensity ...
0answers
24 views

### Energy density and specific intensity

How to derive this energy density from Maxwell's equations and where does the expression for specific intensity come from? I compute a isotropic scatter and I don't know where to get these two ...
3answers
7k 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 ...
1answer
207 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 ...
1answer
114 views

### 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 ...
1answer
195 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 ...
1answer
203 views

### 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 ...
0answers
8 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 ...
2answers
80 views

### 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 ...
2answers
36 views

### 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 ...
0answers
56 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 ...
3answers
281 views

### How to explain the relationship between wave's amplitude and intensity?

I have the following statement which I don't know how to explain: Suppose I have 2 identical monochromatic waves (same intensity and phase) shooting into the same receiver. If each wave's intensity ...
1answer
41 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 ...
0answers
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 ...
1answer
44 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 ...
0answers
53 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 ...
1answer
26 views

### How can I quantitatively compare the average sound intensity of two different audio clips? [closed]

Let's say I have two different sound clips of two different people snoring. The intensity of the audio in both clips will be fluctuating throughout and peak when the person is inhaling. Is there an ...
0answers
25 views

1answer
10k views

2answers
2k 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 ...
1answer
8k 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 ...
0answers
30 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/...
4answers
404 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 ...
0answers
42 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 ...
1answer
40 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 ...
0answers
22 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 ...
0answers
140 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 ...
1answer
56 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)...