Intensity Definition and 898 Threads

Hi, I am not sure if this is an easy question, but I've been looking around and I haven't been able to find some exact equation to this. I performed an experiment where I allowed for a laser beam to go through a cell (of Rubidium-85 and 87) and got the resulting spectrum. The initial [100%]...

Homework Statement A spherical charge distribution is given by p = p_0 (1- \frac{r^2}{a^2}), r\leq a and p = 0, r \gt a , where a is the radius of the sphere. Find the electric field intensity inside the charge distribution. Well I thought I found the answer until I looked at the back of...

Homework Statement In an photoelectric effect experiment , a photoelectric current of 100µA is obtained when lights of 550nm is incident on metal cathode of surface area 1.0cm^2 ... calculate the intensity of the incident light. The ans is 2.26w/m^2 Homework EquationsThe Attempt at a Solution...

Hi!. I´m modeling a gaussiam beam. I found that considering the electric field distribution of Gaussian laser pulses along the axis of propagation, we can write the intensity as: Where y = I_l R is the power is the power reflection coefficient y = w_0 is the beam waist radius at y = z=0...

Sun emits 153.6 x 10^15 J of energy onto a region that is 20km by 20km in area. The intensity of the sun on this region is 685W/m^2. How many days would it take for the sun to put that amount of energy onto the region? I went intensity = power/area and got to a time of some 44000seconds...

What is the decibel level of a sound whose intensity is 4% that of a 95dB sound? I know dB = 10log(I/Io) but don't know how to incorporate this for this question.

Homework Statement Two pieces of polaroid are arranged so they are initially parallel . One of the polaroid is rotated until the intensity of the light beam from the two polaroid is 1/3 of its initial intensity . Calculate the angle turned thru the polaroid Homework Equations The...

So I understand that a black body is a diffuse emitter, and that it radiates energy at a rate of σT^4. I also understand the correspondence between a solid angle and the superficial area of a sphere. dS=r^2sin(θ)dθd\phi=\frac{ds}{r^2}=d\omega=\frac{dAcos(\alpha)}{r^2} What I don't...

So I understand that a black body is a diffuse emitter, and that it radiates energy at a rate of σT^4. I also understand the correspondence between a solid angle and the superficial area of a sphere. dS=r^2sin(θ)dθd\phi=\frac{ds}{r^2}=d\omega=\frac{dAcos(\alpha)}{r^2} What I don't...

For a double slit experiemnt, the bright fringe has intensity of I, when one of the slit is covered, the intensity is 0.25I. In my opinion, the slit now become single slit, so it has area of half of the initial area, but we know that power is the product of intensity x area, by keeping the...

Hello PF'ers, Why is it that two light-bulbs produce twice as much brightness as a single light-bulb would? If we restrict our attention to a single point in space where light from the two sources meet, the waves would cancel half of the time and reinforce half of the time, producing on...

Homework Statement Given, E=ar20/r2 (mV/m) in free space,find ρv at the point (3,-4,1)(cm). where, ρv=Electric charge density per unit volume E=Electric field intensity Homework Equations ∇.(εE)=ρv The Attempt at a Solution ε∇.E= -2\frac{20ε}{r^3} for point (3,-4,1)(cm)...

Homework Statement A source prodeuces sound of intensity level of 30dB .If another source prodeuces sound at the same time , what's the resultant level?Homework Equations The Attempt at a Solution the ans is 10 log (2##I_1## / (##I_0##)) = 33dB , but why not = 10 log (4##I_1## / (##I_0##)) ...

Homework Statement A motorcyclist travel at cnstsant speed of 72km/h along a straight road toward an obesrver standing at the centre of bridge over the road . When the motor cyclist is distant, the obesrver hears a sound of 65hz from the engine of the motorcycle. What would be the frequency...

Homework Statement the factor affecting sound intensity is amplitude and frequency . why not also the distance from the source (r) , in my opinion, intensity = power/area , so the intensity = power/ 4 pi r ^2 ... so I is inversely proportional to r^2 ... Homework Equations The...

Homework Statement the factor affecting sound intensity is amplitude and frequency . why not also the distance from the source (r) , in my opinion, intensity = power/area , so the intensity = power/ 4 pi r ^2 ... so I is inversely proportional to r^2 ... Homework Equations The...

I am currently autodidacting the basics of astrophysics, and I of course came across the term specific intensity. The book explicates that it is defined as the differential of intensity per frequency element. But is there a better explanation so that I could lean closer towards a visualization...

[SIZE="4"]Definition/Summary Intensity of radiation = power per area perpendicular to the radiation. It is a vector, parallel to the radiation. Intensity of radiation = energy density times velocity (therefore sometimes called energy flux). It is measured in watts per square metre...

Homework Statement here's the question , ans any my hand written working. which one is correct ? my ans or the model answer? Homework Equations The Attempt at a Solution

Homework Statement when a stone is thrown to position O (in a pond), a wave is generated and the wave eventually spread out form the center, my question is will the amplitude of particle of A, B and C change? the wave intensity is I= 0.5m(w^2)(a^2)s^-1/ 2 pi r so i have i got I is...

Homework Statement since we know that the intensity of wave is I=P/A P =power, A=area so I = 0.5m(w^2)(y^2)/4pi (x^2 ) so i got I is directly propotional to (y^2)/ (x^2 ) but there's variable x in the eqaution of y... so can i say that I is directly propotional to y^2 / x^4...

Hey there. My goal is to understand the origin of the main forces that keep together an optical lattice created by two identical counter-propagating laser beams. I quote a small excerpt about the forces in optical molasses with high intensity, which I'm having trouble in understanding...

I have a doubt that can we increase the intensity of light without changing its amplitude and by increasing its frequency ? :what:

Homework Statement Three speakers with the same effect are connected to the same tone generator are placed along the y-axis and sends out sound in equal directions. The distance a and b are in the same magnitude as the wave length of the sound...

The power density of an electromagnetic wave is proportional to the absolute square of the electric field |E|^2 (assuming a plane wave). Here, E is a vector so the absolute square involves all three of Ex, Ey, and Ez. In homogeneous, linear media, it's easy to show that each component of E...

Homework Statement Imagine a 10 cm thick slab of flesh. If your x-ray imager can reliably identify a 5% change in intensity from one location to another in an image, what is the smallest diameter bone you are going to be able to make detect in your x-ray image? Absorption length of bone...

So I understand that to calculate the intensity a distance d away from a light-bulb you would treat the light-bulb as a point source and do a gaussian-sphere-type-of-thing to figure out the intensity at the desired location. My problem involves a solid object made up of "point" light sources...

A test question I was asked earlier in the year has been hanging around in the back of my mind: "If a radio is moved 3x further away from you, how is its loudness affected?" To answer this question one needs to know what determines the loudness of sound. What determines the loudness of...

Homework Statement Here is the pic: http://i.imgur.com/olnuDjL.jpgHomework Equations The Attempt at a Solution So intensity was pretty easy, it came up to be y=\frac{GM}{a^{2}}(1+\frac{1}{2\sqrt{2}},1+\frac{1}{2\sqrt{2}}) Check on if it's correct would be nice aswell. Now for potential I know...

I read that if a beam of unpolarized light goes through a polarizer, the intensity of the polarized beam is equal to half the intensity of the original beam. Can someone explain me why? I thought the intensity would be the same.

the intensity of iturninacion at any point is proportional to Ia intensity of light source and varies inversely as the square of the distance from the source. if two sources, A and B intensities, are at a distance D, at what point on the line that joins them, thee intensity of Lighting will be...

You are in a park when you spot your friend 100 m away. At what lowest decibel should you shout your greetings so that your friend can just hear you? Assume that your friend has normal hearing. My prof never gave an example of how to do this and I can't figure it out. The correct answer is...

Homework Statement Two speakers with the same power output generate sound waves in 360 degrees direction. Both speakers have the same freuqncy and the distance between the speakers is given. How can we from this calculate the sound intensity at any given point around the speakers...

Homework Statement After a laser beam passes through two thin parallel slits, the first completely dark fringes occur at ±14.0∘ with the original direction of the beam, as viewed on a screen far from the slits. A)What is the ratio of the distance between the slits to the wavelength of the...

So a lossy dielectric sphere gets an initial charge distribution evenly across the sphere. Find an expression for E inside and outside the sphere for all t. I figured that σ∇E=dp/dt p being volume denity. So I apply spherical coordinates to the div of E and integrate over r to get...

Homework Statement A loudspeaker emits sound isotropically with a power of 100db. Find the intensity in w/m at a distance of 20 from the source Homework Equations Intensity=power/area, For sound wave... power=ro*a*2pi^2*f^2*v*A^2, and I=2pi^2*ro*f^2*v*A^2. db=10log_10_(I/I_0_)...

Homework Statement Two loudspeakers are placed beside each other and produce sound of the same intensity at the position of a listener. One speaker produces a low note of 40 Hz and the other produces a high note of 2560 Hz. What is the ratio of the maximum displacements of the speakers...

I'm a little confused about a small detail when finding the intensity over the screen, as some notes I'm using happen to calculate the same thing twice, with a slight difference the second time. Each method does the following Call the electric field at any point E so we have...

Homework Statement Light of intensity I0 passes through two sets of apparatus. One contains one slit and the other two slits. The slits have the same width. What is the ratio of the out going intensity amplitude for the central peak for the two-slit case compared to the single slit?Homework...

Here's a question I'm working on. I've managed everything uptil the first bolded part, then I get stuck there. I have no idea how to estimate the relative intensities of coherent and incoherent light. I've had a look at tonnes of formulas for the intensity of light but can't find one which would...

Homework Statement When light of wavelength 630 nm is directed onto a photocell, electrons are emitted at a rate of 2.6 *10 raised -12 C/s. Assume that each photon that impinges on the photocell emits one electron. How many photons per second are striking the photocell? How much energy per...

If you have two sound sources emitting the same frequency and in phase with each other such that the emitted waves destructively interfere along the line containing the two sources, is the intensity at the points 0 or the sum of the intensity of each source independently?

Hi, does the intensity change when circularly polarised light passes through a linear polariser? I am thinking of a flow like this: natural light -> vertical linear polariser -> quarter wave plate -> horizontal linear polariser -> intensity? After the first polariser, the intensity is 50%...

It is written in my book that the Electric intensity is the amount of electric charge which passes in one second. I think the definition is incomplete, I mean it didn't mention the sector that it should pass in one second or the distance, does it mean the amount of electric charge which passes a...

Homework Statement A wave has an amplitude a1, intensity I, and frequency f. A second wave of the same type has twice the intensity and double the frequency, find the amplitude of the second wave in terms of a1. Homework Equations Using the relationship I=k a2f2, where k is a constant...

Not a homework... simple curiosity by trying to know this a bit better in order to learn and understand possible effects of sound to marine mammals auditory systems. In sea water, at distance of 1m from a localized sound source, you measure the intensity level as 237 dB. How far away from the...

Homework Statement I know that intensity is power per unit area. When I do a dimensional analysis, it reduces down to mass per cubic time. Is there any physical significance to that? Homework Equations I=P/A The Attempt at a Solution

If I have a sphere with radius r, a distance d away from a sound source of intensity I0. What will the intensity I of the sound wave be on the point of the sphere directly opposite the source? Preferably I would like to find the intensity of the wave at any point on the sphere.

Homework Statement I don't seem to understand the proper intuition behind the electric field intensity potential difference relation? please can anyone explain it with solid intuition and maybe a good analogy...and can anyone give a short analogy about the concept of electric field...

Homework Statement The electric field intensity at a point between two large parallel plates is 4.8 × 102 N/C. What does the electric field become, as a result of each of the following changes, considered separately (the plates are isolated), (a) when the distance between the plates...