Intensity Definition and 898 Threads

Dear forum, I want to capture the light from a rectangular area by a monochromator in order to analyze the average intensity of the entire area, at specific wavelengths. The monochromator is at a fixed distance from the scene. What type of arrangement do I need (lens, collimator?, et.c.) ...

I don't have a strong technical background in this, so need some help. I'm currently investigating pulsed electromagnetic field (PEMF) devices to rehab injuries, and trying to figure out the best applicator and placement. The choices available are coils, mats, butterfly coils, paddles, and a...

Hello All. I looked at a question "A noisy machine in a factory produces sound with a level of 80 dB. How many identical machines could you add to the factory without exceeding the 90-dB limit?" The solution in link below assumes the intensity will increase n fold if I add n machines. Why is it...

In the Hanbury-Brown and Twiss (HBT) family of experiments, they multiply the intensity signals from two detectors. Instead, what if we subract the signals? In this case, we should see the RMS type noise addition when the detectors are far apart, decreasing to a null when the detectors are...

I have the measured magnitudes of a satellite object in four filters and I want to convert this into into Radiant Intensity. I was told that if I integrated the solar spectrum over my filter bandpasses , I could obtain the visual mag of the sun in each of these filters and use this to obtain the...

My answer is (D) but the correct answer is (B). I thought the intensity will be 4 times since the slit width is doubled and amplitude becomes twice. What is my mistake? Thanks

I don't know if the capacitance of a capacitor is large, the capacitor will discharge with greater intensity than other capacitors with the same voltage but smaller capacitance, right? Thanks

The answer key is the light is directed through one polarising filter then filter is rotated and the light changes intensity. I don't understand how that proves that the light is plane polarised. I think if the light is unpolarised, the intensity will also change when it passes through...

My question is specifically with calculating the intensity. The book solution is I=P/(4*pi*r^2) but would this not give me a weaker electrical amplitude in the final calculation after plugging it in to I=(1/2)*√(ε0/μ0)*(E02) ?

Pretty much, I was picturing a 1x1x1 meters cube of a dark colored, mostly uniform material (limited porosity, no crevices) with a small chamber in its interior - exactly where the center of mass should be. In it, a body emitting light is activated with the goal to find the intensity necessary...

This is problem 62 in Cutnell & Johnson's Physics (9th edition): Suppose that the light falling on the polarizer in the figure is partially polarized (average intensity \bar S_P) and partially upolarized (average intensity \bar S_U). The total incident intensity is \bar S_P+ \bar S_U and the...

Consider the infrared led TSAL7600 which has the following properties: $$ \Phi = 35 mW $$ $$ I_e = 25 mW/sr $$ The half angle is ## 30^\circ ## and: $$ I_r(\theta) = cos^{4.818}(\theta) $$ is a good approximation for the relative radiant intensity. However, finding the actual radiant...

The data collected from the experiment is, The first column is the polarizer angle measured in degrees. The second column is recorded intensity measured in lux. The third column is the transmitted intensity measured in lux. This is equal to the recorded lux - ambient lux The fourth column is...

I was looking at the gamma radiation data from IAEA's website: (https://www-nds.iaea.org/relnsd/vcharthtml/VChartHTML.html) and was confused by the absolute intensity listed in the page. I Googled it and it seems to be the probability of emission but why it doesn't add up to 100%? For example...

TL;DR Summary: How do i find the intensity of this wave? I know I is proportional to amplitude / frequency squared, but I don't know what equation this comes from. And I don't know how to answer this.

If I have on my PC let's say sound on 50% and I increase it on 100%, how would the sound intensity change? Would it be twice bigger? But I think that function of sound intensity level dependent on sound percets is a linear function, isn't it? How to explain it? Why is it the linear function?

My answer is 0.5 m (same as wavelength) but answer key is 1 m. I thought the maximum intensity occurs at antinode and distance between adjacent antinodes is half of wavelength so the distance between first and third antinode is one wavelength. Where is my mistake? Thanks

I have realized EIT with continuous laser. What are the requirements for the intensity, duration and repetition frequency if EIT is realized with pulsed laser? you can attach any reference:biggrin:thanks a lot!

I am calculating Responsivity of a pn junction photodiode (a.k.a the target) by irradiating radiation from LED sources. For this purpose, i have two LEDs, one UV and another green LED. Note that LEDs are placed close to the target.UV LED : Manufacturer has given total radiant power to be 20mW...

a) ##\rho = \frac{I}{c} = \frac{F}{A}## for a perfect absorber ##F = ma## where ##a = \frac{c}{t}## ##\frac{I}{c} = \frac{mc}{tA}## ##I = \frac{I^2 tA}{mc^2} = \frac{P}{A}## ##P = \frac{I^2 tA^2}{mc^2} = \frac{W}{t}## ##W = \frac{I^2 t^2A^2}{mc^2}## I am unsure what A is. I think it should be...

Here is the solution, I understand how they got E, but I don’t see how they could get E’ from cosine addition formulas? I don’t need to know how to do it with complex numbers.

Here’s an image of the equations better layed out here’s the solution, I don’t understand how they are squaring it to get the time average

I found there is kind of solution in Pointon's book: An Introduction to Statistical Physics for Students. But I don't know how to find intensity by using frequency.

We assume incident waves to be: y(1)=y(o)sin(wt) y(2)=3y(o)sin(wt+Φ) As Intensity~(Amplitude)^2 We get y(2)=3y(1) This gives us I(2)=9I(1) We assume I(1)=I(o) & I(2)=9I(o) Resultant Wave Intensity I=I(1)+I(2) +2√(I(1)*I(2))*cosΦ ----> I(o) + 9I(o) + 6I(o)cosΦ (We can take cos of this...

I haven't been able to pinpoint a definition of "angular divergence" of a laser so by pure intuition I assumed it would be something like ##\theta=\frac{2R}{D}## and with that I have that the radius of the lase beam is ##R=\frac{D\theta}{2}=90\cdot 5 \cdot 10^{-6} m=450\ \mu m## so...

I'd appreciate if someone could check whether my work is correct. The ##x##-##y## symmetry of the aperture separates the Fresnel integral:\begin{align*} a_p \propto \int_{-a/2}^{a/2} \mathrm{exp}\left(\frac{ikx^2}{2R} \right) dx \int_{-a/2}^{a/2} \mathrm{exp}\left(\frac{iky^2}{2R} \right) dy...

Would we have to use the 3-dB exchange rate? How would we solve this question?

Question: My attempt: Could someone please confirm my answer?

I tried using the equations above, but I wasn't really able to come up with an intuitive explanation. From my understanding, the electric field vector only varies in the x-y plane while the magnetic field vector only varies in the z-y plane. Also, both vary sinusoidally and both reach extrema...

In a single slit diffraction experiment, when we want to calculate the intensity of light on a screen located very far away from the slit, usually Huygens' principle is adopted as a model to perform the calculations. It is assumed that the width of the slit consists of an infinite number of...

Hello. I am having some trouble to understand the resolution of this question. We could easily try to calculate the electric field relative resultant at the screen. The problem i am having is about the amplitude of the electric field: Generally, we have that the intensity part dependent of the...

I was supposed to find the relation among the coefficients $T$ and $R$ which represent the amplitude of the reflected electric field and the transmitted electric field respectively, that is, $$E_{R} = E_{i} R, E_{T} = E_{i} T$$ as well as the coefficients $t$ and $r$, that represent the...

Let a spherical wave propagate from the origin, $y = ADcos(wt-2\pi r/ \lambda)/r$. Also, let a plane wave propagate parallel to the x axis, $y = Acos(wt-2\pi r/ \lambda)$. At x = D there is a flat screen perpendicular to the x axis. Find the interference at the point y on the screen as function...

My Try: The resultant field is given by $$\begin{aligned}\overrightarrow{E}=\overrightarrow{E}_{1}+\overrightarrow{E}_{2}=\widehat{i} E_{0}\cos \omega t+\widehat{j}E_{0}\cos \left( \omega t+\phi \right) \\ \Rightarrow E^{2}=E_{0}^{2}\cos ^{2}\omega t+E_{0}^{2}\cos ^{2}\left( \omega t+\phi...

Hi, If I build a machine that its sole purpose is to radiate xx Hz of electromagnetic wave, how do I calculate the intensity of the waves? Let's say I put it in the room of 30 sq meters. Thank you.

When the crystal above is illuminated with light of intensity ##I_0##, what is the intensity at the central maximum? (The picture shown above is a 4 x 4 unit cell of the crystal) The answer is ##(\frac {5} {16} )^2 I_0##. Why? Apparently, Electric field is proportional to the transparent area...

considering that a simple mirror may reflect 99.9% of the visible light

This the photo of my textbook, Here In the derivation of Electric Field Intensity due to an infinitely long straight uniformly charged wire - In the figure 1(c).20 Vector E1 and vector E2 are electric fields at point P due to the two line elements as shown in the figure 1(c).20. But, in this...

In Principles of Lasers by Svelto, while deriving the Planck radiation formula, equation 2.2.3 says $$I_{\nu} = \frac {c_0} {4n} \rho_\nu$$ where ##I_\nu## is the spectral intensity at some hole in the cavity wall (energy per time per area per frequency), ##c_0## is the speed of light in...

I actually am not sure what equations are relevant here but I thought these are the relevant ones. My Approach: By Stefan-Boltzman Law, the intensity absorbed by the Earth is given as ## I = e \sigma T^4## where e is the emissivity of Earth, ##\sigma## is Stefan-Boltzman constant and T is the...

I = 1/2 ρvR²w² I = 1/2 *1.2kg/m³*340m/s*(10 x 10^-6m)²*(2π*440/s)² I = 0.16 W/m² This is my answer which does not match the given answer. Am I doing wrong?

\begin{equation} \chi = n \sigma \end{equation} Where Chi is the Opacity, n is the number density of absorbers (constant), and $\sigma$ is the cross section(given). We define the optical depth is just the number of photon mean-free paths in a given physical step, i.e. if we consider a...

My attempt: p and T allows us to calculate ##Z=402 \frac{kg}{sm^2}## using ## Z=p*\sqrt(\frac{\gamma*M}{R*T})## . The sound intensity level at 10 meters allows us to calculate the intensity at 10 meters to be I=10``````^{-7} W/m^2 using ##50 = 10*log(I/I_0)##. Then, using the formula...

Hello there, I've worked through this problem and I would just like to check whether I've understood it correctly. I found ##\vec H##, ##\vec B## and ##\vec M## using Ampere's Law and the above relations as I would for any thin current carrying wire and these were my answers: $$\vec H = \frac I...

what I've done so far? -i've determined the vector between the point (4, 0, 0) and the point P. (4, 6, 8) - (4, 0, 0) (0, 6, 8) -The norm of this vector is the radial distance of the line to point P (the value of “ρ” in the formula) √(0^2 + 6^2 + 8^2) = 10 -> ρ = 10 -and its unit vector is...

The answer is about 40 Watts, but i am really not getting it: <Pot> = 0.5((pλ)(ωA)²)v p density linar λ wavelength ω angular frequency A amplitude v phase speed Why is this wrong? (I already tried too by <Pot> = Z*(ωA)²/2) Z is impedance

1. speed of light = 3*10^8 ms^-1 length of an Earth year=365 days*24 hours*60minutes*60seconds=3.15*1 0^7 seconds distance=speed*time 1 light year= 3*10^8 *3.15*10^7=9.46*10^15m 4.2 light years = 4.2*9.46*10^15m=3.9732*10^16m ~ 3.97*10^16m (to 3sf) 2. Intensity=power/area Power=1.4MW=1,400,000...

So I thought of calculating the path differences between all the 3 points by taking them in pairs of 2. S1 and S2 S2 and S3 S3 and S1 I got the path differences as λ/3 , λ and 2λ/3 I can now find their phase differences using the equation Cosx=2π/λ* (path difference) Then I can apply the...

For a star.. Apparent Magnitude = -2.5log10 I K And I = I0/d^2 So in terms of I0... Apparent Magnitude = -2.5log10 (I0/d^2) And the Stefan-Boltzmann law says: Energy Flux = Sigma(T^4) In my reading it says that Intensity is the energy emitted per unit of area per unit of time. It says the same...