# Questions tagged [intensity]

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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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### 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 ...
1answer
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### 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 ...
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### Does the intensity of LED lights decrease after turning on?

LED lights come on immediately the power is supplied. This is different to the older compact fluorescent-tube lights. I am always impressed by the brightness of the LED lights when they come on. Later ...
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### 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 ...
0answers
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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 ...
0answers
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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
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### 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 ...
1answer
48 views

### Is there a math formula to calculate difference of dB of sound, in different pure transmitting mediums?

Is there a math formula to calculate the difference of dB of sound, in different pure transmitting mediums? For example, based on a measurable decibel level, with a known frequency, a known atomic ...
1answer
88 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?
1answer
38 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 ...