Questions tagged [intensity]

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Angle of incidence between two successive polarizers [closed]

I'm trying to figure out a question I had about the angle between the transmission axes of two successive polarizers: If the first polarizer has its transmission axis parallel to the y-axis and the ...
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DIffraction Grating vs Single slit diffraction

Why doesnt single slit diffraction ressemble to diffraction grating from multiple slits? In multiple slits we have the number of hygens sources as the number of slits N.In single slit diffraction,cant ...
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33 views

Dependence of solar energy absorbed over a year on orientation of solar panel

I am trying to find how total solar energy incident, over a year, depends on the orientation of a tilted solar panel. The final goal is to find the optimum direction in which the panel should be ...
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1answer
23 views

Net intensity for interference from incoherent sources

Why do we simply add the intensities for interference from two incoherent sources? What's the proof for that? I know that incoherent means that their phase difference changes with time
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2answers
52 views

Would a perfectly collimated laser beam have a flat intensity distribution?

I'm trying to simulate a collimated laser beam in some FORTRAN and am wondering about the intensity distribution of a perfectly collimated beam: would it be a flat distribution (equal intensity across ...
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How to calculate the intensity profile of a pulsed laser beam given its pulse energy?

I am trying to calculate the intensity profile of a pulsed laser given that the intensity envelope is Gaussian. I also know the full width half maximum and pulse energy of the pulse. What are the ...
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1answer
52 views

Intensity of light at a point [closed]

Unpolarized light of intensity I scattered from point A. Intensity of light perceive by given observer is :-Diagram Unpolarized light has vibrations in all planes. And at a point A in its path the ...
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13 views

Temperature and light relationship

Is the absorptivity of light affected when the temperature of the solution it passes through changes? For example consider a Beer Lambert experimental set up. If the temperature of the solution ...
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20 views

Can high energy photons produce more photo current than a bit more intensity of photo electrons?

If we take 2 case : Case 1: Very high energy photons and a bit less intensity Case 2: less energy photons but a bit high of intensity In both case ,both energy of photons are greater than the ...
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33 views

Intensity of spectral lines

Why are certain spectral lines more intense than others, that is why certain transitions between levels have greater probabilities of occurrence than others?
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3answers
129 views

What is happening on the screen as you reduce the slit width? How can you demonstrate that mathematically? [closed]

I think in the case of a single slit, as you reduce the slit width the central peak decreases. The width decreases the amount of light entering the slit actually decreases,so when the area under the ...
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21 views

How to calculate a lattice constant from scattering electrons? [closed]

Does someone know how to solve that problem? Is it using Bragg's law? I know that in Bragg's law, the incident angle and reflection angle are the same but in the picture it is not. Problem: When ...
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1answer
40 views

How does amplitude affect photon's intensity as a particle?

Considering the scenario were a photon acts as a particle, how does amplitude affect the photon? Does it increase its intensity? How do you visualise this?
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36 views

Radiant Intensity

Radiant intensity is power per unit area and area being perpendicular to propagation of energy. Moreover, intensity varies inversely with square of distance. My question is if a beam of light is ...
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28 views

How do you calculate intensity given the energy of a wave?

I’m a bit confused when it comes to calculating intensity versus energy of a wave. If I’m given a wave with an energy of 1 eV, how do I calculate its intensity ? I know intensity is usually measured ...
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1answer
25 views

Average acoustics power of sound

We know that acoustics power of sound is equal to intensity of sound times area of the sphere centered with sound source, but my question is what is average acoustic power and if there is any ...
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42 views

intensity of sound waves

I have come across two formulae for intensity of sound waves, I= P/A what changes from place to place obeying inverse square law and the other, I= 2π2ρAf2∆s2,what gives average intensity and does not ...
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1answer
26 views

Nicol prism as analyzer

I recently read in my notes when circularly polarized ray are passed through Nicol prism then there is no variation in intensity. But When it is first passed through nicol prism ordinary ray will ...
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30 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 ...
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117 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 ...
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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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2answers
138 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 ...
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67 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 ...
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60 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 ...
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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 ...
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1answer
42 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 ...
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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 ...
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1answer
48 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 ...
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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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1answer
27 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 ...
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4answers
4k views

Does light intensity oscillate really fast since it is a wave?

If you shine light on a wall, what will be seen is a "patch" with constant intensity. However, if light is viewed as a wave, then it is oscillations of the electromagnetic field changing from 0 to the ...
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1answer
35 views

Luminostiy, Flux, Intensity definitions and meaning

I am taking astrophysics course and we are constantly talking about Luminosity,Brightness,Intensity,Flux etc. I thought that I understand the idea properly but I see now that I dont. Intensity is the ...
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3answers
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Intensity of the resultant of two complex waves [closed]

Suppose I have two waves: $Y_1= a_1e^{i(wt-kx1)}$ and $Y_2= a_2e^{i(wt-kx2)}$ I know by superposition $Y= Y_1+Y_2$ and intensity $(I) = |Y|² $ But how can I solve it. It seems hard for me to find the ...
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Photoelectric effect - the reason for exponential graphs and a misconception about the concept of intensity

We have this basic PASCO Photoelectric Effect equipment in our lab and there are two things I would like to ask about the experiment. We keep either the area apertures or wavelength filters fixed and ...
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1answer
126 views

Reflection coefficient derivation

from fresnel equations we have $$r_{parallel}=\frac{n_1\cos\theta_i-n_2\cos\theta_r}{n_1\cos\theta_i+n_2\cos\theta_r}$$ $$r_{perpendicular}=\frac{n_2\cos\theta_i-n_1\cos\theta_r}{n_1\cos\theta_i+n_2\...
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1answer
390 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 ...
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3answers
418 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 ...
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361 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 ...
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1answer
271 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 ...
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1answer
126 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 ...
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2answers
432 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
41 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
805 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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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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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
137 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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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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2answers
39 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
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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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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 $...