Intensity Definition and 966 Threads

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...

Homework Statement Hello! This is really a simple question about how to use reflection and transmittance coefficients. I have a light ray of intensity I0 comming (S-polarized) to a glass surface at a certain angle, like in the picture: I want to find the intensity of the reflected...

Quantifying an "Off-axis" Neutrinos (probability and intensity) Considering the modelling of a high energy proton beam neutrino experiment. I have questions concerning the scattering of neutrinos from the axis of the proton beam. I understand that a muon beam (derived from a proton beam)...

Homework Statement An alarm clock makes a sound that has intensity 60 dB at a distance of 1 m. What is the sound intensity of 100 such clocks which are all 100m away? (A) 0.6 dB (B) 40 dB (C) 50 dB (D) 60 dB Homework Equations I1/I2 = R2^2/R1^2 The Attempt at a Solution If...

Homework Statement At 1 m away from the source of a sound, the intensity of the sound is 90 dB. At 10 m away the intensity is…? The answer is 70 dB but I don't know how... Homework Equations I = Power/Area The Attempt at a Solution My thought was to set up the equations...

A few months back my colleagues and I are facing a problem where the intensity of our sapphire peak fluctuates every time an XRD phase analysis was done, even when the scan was done on the same sample. By accident, I found that the orientation of the sapphire substrate with respect to phi...

Hi, I try to solve excercises from the book Stellar Atmospheres by Mihallas. I'm stuck on this one: By use of Snell's law, n_1(\nu)\sin{(\theta_1)}=n_2(\nu)\sin{(\theta_2)}, in the calculation of the energy passing through an unit area on the interface between two dispersive media with...

Homework Statement Initially unpolarized light is shining on a series of six polarizers in a row. Each polarizer is rotated by the same angle, θ, relative to the previous polarizer. Choose a fraction (anything less than 1) as your final intensity. What is the angle, θ, such that the...

Homework Statement One wheel goes at 850 rpm and the other at 780 rpm, and obviously they make a noise. Standing in an enclosed room, you hear the sound intensity increase and then decrease periodically due to wave interference. How long does it take between successive times for the sound...

Can someone please explain why the are used is 4∏D2? Shouldn't it just be ∏r2?

Homework Statement A point source of sound emits energy equally in all directions at a constant rate and a person 8m from the source listens. After a while, the intensity of the source is halved. If the person wishes the sound to seem as loud as before, how far should he be now from the...

Homework Statement Two loudspeakers A and B of equal power are separated by a distance of 1.4 m. Both the speakers emit sound waves in phase and of frequency 450 Hz. If a microphone were to be moved from A in a direction perpendicular to AB, at what distances from A will it detect a minimum...

I'm a bit confused because the sun's radiation & heat are passing through space (with some passing through planets' atmospheres), and there is almost nothing in space, therefore, how does that immense heat & light just diminish over AU distances when its going through almost nothingness? What...

Homework Statement Infinite uniform line charges of 5nc/m lie along the (positive and negative) x and y axes in free space. Find E at :P(0,3,4) Homework Equations E due to line charge along the Z-axis is given by: E=(λ/(2∏*ε*r))*ar where λ=line charge density;ε=...

I know that this question may sound silly , but I really can't get the difference between intensity and density in general ! And the whole magnetic field thing makes it worse , in my textbook , its written that magnetic field intensity is the same as magnetic flux density , but no matter how...

Homework Statement A beam of polarized light is sent through a system of two polarizing sheets. Relative to the polarization direction of that incident light, the polarizing directions of the sheets are at angles θ for the first sheet and 90° for the second sheet. If 0.10 of the incident...

Homework Statement Two infinitely long filaments are placed parallel to the x-axis as shown in Figure 1. a)Find H at the origin b)Find H at (-1,2,2) Homework Equations ∫Hdl=Ienclosed H=H1+H2 The Attempt at a Solution Well following the equation above I get Hl= Ienc then...

I have just completed an experiment on principles of lasing, constructing a laser and measuring the beams intensity distribution. This distribution of the beam was measured using a detector mounted on a traveling microscope. The detector had a pinhole cover such that only a small fraction of the...

Homework Statement I need to derive the intensity distribution of the double slit experiment. Intensity as a function of the slit separation d, the distance to the screen L and the wavelength \lambda. L>>d Homework Equations The Attempt at a Solution Ok this is ridiculous but...

According to my prof, increasing intensity of the light source in a photocell for the photoelectric effect does not increase the kinetic energy of photoelectrons emitted. Instead, the number of electrons emitted (and current) increases. Changing the colour of the light causes an increase in...

A reading from e=mc2 by David Bodanis, The big question though is why? Why is squaring the velocity of what you measure such an accurate way to describe what happens in nature? One reason is that the very geometry of our world often produces squared numbers. When you move twice as close...

I am struggling with a derivation that calculates the cross sections for Mie scattering and since the incident light is considered to be a x-polarized plane wave I thought that we would have[ tex ] I_i = \frac{1}{2} \sqrt{\frac{\epsilon}{\mu}} \vert E_0 \vert^2 [ /tex ] , but I do not understand...

This is something I don't relly get. I keep reading that the intensity of a wave is proportional to the square of its amplitude. So let's suppose we have a random wave source, with amplitude A0. If we replace that source with five identical copies of it, their collective amplitude is 5A, yes...

This is something I don't relly get. I keep reading that the intensity of a wave is proportional to the square of its amplitude. So let's suppose we have a random wave source, with amplitude A0. If we replace that source with five identical copies of it, their collective amplitude is 5A, yes...

We know that the intensity of the light in the light bulb depends on the electric current. And I want to know who was the first physicist who proved this. And if there is a possibility could you also tell me how, why, when, where he did this experiment or give me an website, but the name of...

Hi guys, let's say we have a wave where the power P is proportionate to the square of its amplitude, which is A^2. If now we have 2 identical waves in superposition in phase, then we have an amplitude of 2A am i right? Next, we realize that because of the amplitude of the superposed waves is...

Here's a question I got on an exam: During a typical workday (eight hours), the average sound intensity arriving at Larry's ear is 1.8 x 10-5 W/m2. If the area of Larry's ear through which the sound passes is 2.1 10-3 m2, what is the total energy entering each of Larry's ears during the...

Good afternoon all My question is, when we observe stationary waves, and we know that at a certain point, the sound is maximum, is this the displacement node or the displacement antinode? I have read a few different sources and currently i have encountered both. To me it makes more sense...

Hello all, I'm a new Mechanical engineering graduate student who needs help using a photodiode. I'd like to rig up some kind of circuit that will let me measure the intensity of laser light. This is kind of a new area for me haven't really done anything like this before so forgive me if I come...

What is the equation to find relative sound intensity from a source when given the angle?

Hello, I am currently working on a problem to calculate the light that makes it through a half circle. For example, say I put a cylinder out in the sun, where the intensity is known to be 1030 W/m^2. I would like to compute the intensity/energy/power that makes it into this. Now, given the...

Homework Statement A beam of unpolarized light is incident on a series of three polarizers as shown. The angle of the transmission axis of each polarizer is indicated by the dashed line, with q1 = 110, q2 =230, and q3 = 370 (all defined relative to vertical). What is the ratio of the...

Homework Statement In order to decrease the intensity of a beam of unpolarized light to 10% of its original intensity using two polarizers, what is the required value of θ, the angle between the transmission axes of the two polarizers? Homework Equations tanθB=n2/n1 The...

Hi everyone here, hope you enjoying this summer .. i'm taking ' elements of electromagnetic ' course this summer session and i just have a little question here in the yellow shaded statement shouldn't it be dl = (l/N) dz instead of dl=(N/l) dz ? By the way, it's not a HW...

A +7.5 nC point charge and a -2.0 point charge are 3.0 cm apart. What is the electric field strength at the midpoint between the two charges? just give me the formula ?

Hi, https://www.physicsforums.com/attachment.php?attachmentid=60066&stc=1&d=1372909704 I would like to ask a question on thermal radiation. In the attached image, if all three surfaces \{ dA,d{S_1},d{S_2}\} are black body surface, and d{S_2} = d{S_1} = S, then does d{S_2} receive the same...

I'm having difficulty understanding the solution to this question. "A source creates a sound that is observed at 200 Watts per meter squared. If the intensity level of the observed sound decreases by 20 decibels what is the decrease in observed intensity? The way I solved it was I saw 20...

Homework Statement Question: Calculate the wavelength in mm of the most intensive microwaves Question before: State the intensity of the most intensive microwaves detected Answer: 380 Units. (5 Waves per CM) [Read from a graph] Homework Equations None given. The Attempt at a Solution I...

Homework Statement 1.An unpolarized beam of light is incident on a stack of four ideal polarizing filters. Each of the second, third and fourth polarizers is rotated by 30.0o relative to the preceding polarizer. In this way, the axis of the first polarizer is perpendicular to the axis of the...

Describe the pattern of intensity vs wavelength observed in blackbody experiments and explain why these observations were in conflict with the predictions of classical physics. is this right? the shorter the wavelength, the greater the intensity. This is wht I wrote: Classical...

The electric intensity E, current density j and specific resistance k are related to each other by the relation please explain