Intensity Definition and 898 Threads

Homework Statement A sheet of charge Ps = 2 NC/m^2 is present at the plane x = 3 in free space, and a line charge Pl = 20 nC/m is located at x = 1, z = 4. a) Find the magnitude of the electric field intensity at the origin b) Find the direction of E at P (4,5,6) c) What is the force per...

Homework Statement A certain loudspeaker system emits sound isotropically with a frequency of 1770 Hz and an intensity of 0.892 mW/m2 at a distance of 5.66 m. Assume that there are no reflections. (a) What is the intensity (in mW/m2) at 30.8 m? At 5.66 m, what are (b) the displacement amplitude...

I have LEDs of 0.7mW, but for my experiments, I want my values to be in light intensity unit - W/cm2. I cannot figure out how to do the conversion.

Hello, I need to calculate intensity of light at a distance of 24 inch from a tubular light source with a light intensity rating specified at 3.6 microwatts/sq.cm. per inch of lamp. The light is a UV light which is to illuminating a cooling coil in air conditioning system. Supposedly there...

Homework Statement Henry and Tom see a flash of lightning and then hear the resulting clap of thunder. Henry measures the sound level of the thunder as 65 dB while Tom, who is 800 m further from the event, measures it as 63 dB. Homework Equations The Attempt at a Solution I_H /...

Hi all, I've got a problem with the circuit of the image. The solution (intensity) is given but i would like to know how to get it... Can anyone help me? [PLAIN]http://img191.imageshack.us/img191/9094/circuitf.gif Thanks!

intuitively, i would say that in a CCD, the photoelectrons are being "created" only by the electric field of the incident light, so that the intensity is proportional to |E_x|^2+|E_y|^2, with the xy-plane coinciding with the CCD plane. But I have several papers here saying that the intensity...

Hey, In x-ray tubes, how come an increase in the voltage results in an increase in the intensity of the electrons. i.e. the no. of electrons emitted per unit time per unit second. Thanks.

Does the timescale over which a charge decelerates determine the energy and intensity of brem photons? Consider two electrons, one is decelerated over a large distance and relatively long period of time. A second electron is involved in fast scattering event and loses its energy relatively...

Sound Intensity-- just need someone to check my work :) Homework Statement While enjoyable, rock concerts can damage people's hearing. In the front row at a rock concert, 5m from the speaker system, the sound intensity is 145 dB. How far back would you have to sit for the sound intensity...

I'm trying to find a mathematical formula between applied tension and resulted magnetic field intensity on an electromagnet. I know that between the voltage and the electric current there is a pi/2 offset, but in practice there is a bit more than actually pi/2 offset probably something that...

I am researching how photon intensity attenuates within matter and am a bit confused by what I have come across. Several sources state that the attenuation of photon intensity within matter is exponential (as a function of depth). The explanation is that photon interactions with electrons in...

Homework Statement Two polarizers are out of alignment by 30°. If light of intensity 3.86 W/m2 and initially polarized halfway between the polarizing angles of the two filters passes through the two filters, what is the intensity of the transmitted light? The Attempt at a Solution Use...

Homework Statement Find the sound intensity level of a thunder bolt, if a person is standing 200 m from the spot it hits. The bolt hits the ground vertically and the height of the bolt is 1500 m. The bolt has an electrical current of 20 kA and a voltage of 30 MV. It discharges thrice, each...

Homework Statement Hi, here is the problem I'm having trouble with: The rms value of the magnitude of the magnetic field in an electromagnetic wave is Brms = 0.137 T. The intensity of this wave is approximately... Homework Equations E = cB I = (ErmsBrms) / \mu0 The Attempt at a...

OK so i know it is possible to double the frequency of a light beam by using second harmonic generation by passing the beam through a non-linear crystal; however i am unclear as to the required intensity of light beam that is needed to achieve efficient conversation. Would it be possible to...

Hi. During daytime sea water having poor solar reflectivity remains warmer than the air. But at times, water has also been found to be colder than air, with the difference being 5-10 degrees C. Can anyone please justify how could that be possible?

Hi,Homework Statement I have the following question: I found two formulas given for the intensity after polarised light went through a polarisation filter. Homework Equations I_{1}=I_{0}*\frac 1 2 and I_{1}= I_{0}*cos^{2}(\phi) The Attempt at a Solution Well I don't know when to use...

Homework Statement Calculate the threshold ionization intensity for hydrogen gas. The attempt at a solution The way I tried to work it out was to use the field intensity of air which breaks down at, 3x10^6V/m. The ionization potential of oxygen is 13.618ev, 14.534ev for nitrogen and 13.598ev...

what is the difference between the electric field intensity of 1)infinite plane charged sheet whose formula is E=\sigma/2\epsilono and 2)infinite conducting charged sheet whose formula is E = \sigma/\epsilono

electrostatics --- calculation of electric field intensity Homework Statement My aim is to calculate electric field intensity at a point P where the test charge qo is kept which is at a distance r from the source charge q is kept. Homework Equations Why it has mentioned limit qo...

If I=s/4pir2 would It be correct to write this in terms of logs like this:. lnI=(lns/4pi)-2.lnr Also how could this relate to y=mx+c? I think it's y=lnI. X=lnr. -m= -2 and c= lns/4pi. Is this correct? Thank you

This is weird, I have no clue on how to solve the following question that I "invented" while walking in the street due to car sounds. I know that the intensity of sound -let's say the source of sound is a dot/point- decreases as 1/r² do. If I'm at a distance 1 m, I can hear 4 times "stronger"...

I was just wondering if, through all the fusion test done over the years, if anybody has ever mesaured the lux given off dureing a reaction?

Homework Statement Two wave generators S1 and S2 produce water-waves of wavelength 4m. They are placed 4m apart in a water tank and a detector P is placed on the water surface 3 m from S1. (90 degree to S1S2, S2 to P is 5m) When operted alone, S1 and S2 produce waves with intensity I and...

Homework Statement Proton of mass m and charge e is moving in arbitrary direction in external homogeneous constant electric field E. Show the intensity I of quadrupole radiation as a function of proton speed and magnitude of electric field. The Attempt at a Solution I have similar...

After looking at the graphs of single slit and double slit interference of intensity vs. angle, it seems that the intensity drops off very steeply with single slit interference but doesn't drop off at all with double slit interference patterns. Why is that?

Hello! could you help me with this? I´m from biology field and have some difficulties with the following calculation: I want to estimate how much mor UV is coming from a mercury short arc lamp of a fluorescence microscop compared with the sun UV, so that I use the right eye protection for...

Is there any quantitative relationship between luminous intensity of monochromatic light and flux of photons(number of photons/(area*second)) ?

How would I calculate the magnetic flux density of the magnetic field generated by eddy currents induced in a circular plate? I decided it would be reasonable to approximate this by considering the flux density of a current loop. However, it is my understanding that eddy currents are induced...

Homework Statement [PLAIN]http://img855.imageshack.us/img855/7899/physicsch3333.png Homework Equations I = 0.5*I_0 I = I_0*cos^2(θ) The Attempt at a Solution I_1 = 0.5*I_0*(cos 50)^2 I_2 = I_1*(cos 70)^2 I_3 = I2*(cos 50)^2 This is my attempt at the problem. This is new to...

Homework Statement A sound-level meter placed 150 mm from a small sound source records a reading of 45dB. What is the intensity at that point. Homework Equations I m using this equation IL = 10 log(I/I.) where I. is the lowest intensity i think which should be 10^-12 W/m^2. The...

[b]1. The problem statement, all variables and given/knownThe diagram shows three small charges at three corners of a rectangle; charge A is -12µC, charge B is -15µC and charge C is +8.1µC. Calculate the magnitude and direction of the electric field intensity at the fourth corner, D. The...

Homework Statement We are looking at gravitational field intensity in particular here, and using the Earth as an example. The question states: Calculate the gravitational field intensity at a height of 300.0 km from Earth's surface. Why is it that: Since the point in question is outside of...

Hi Guys, I am working on some fluorescence correlation spectroscopy and I have some data generated by the machine I use. The data has the correlation plot of G(tau) vs the delay time (tau) which is an exponential decay. The data also has the count rate given for the duration for the...

Homework Statement An astronomer is trying to estimate the surface temperature of a star with a radius of 5.0*10^8m by modeling it as an ideal blackbody. The astronomer has measured the intensity of radiation due to the star at a distance of 2.5*10^13m and found it to be equal to 0.055W/m^2 ...

Ok so I was sitting out back one day listening to some music with some friends around. We had some music playing on a stereo inside the house and we were out the back with the glass door open about 10 cm's. I thought I noticed that some sounds with different frequencies seemed louder then...

Homework Statement Three sources are emitting sound at 0.8W, one at 200 Hz, second one at 201 Hz and third one at 202 Hz. The sound travels in a shape of a half sphere. Find the intensity at 3m distance from the source (the sources are said to be very close to each other so I guess they can be...

Homework Statement The helium-neon lasers that we use in lab produce light waves with an average power of 0.85 mW. Suppose that at a distance of 1.0 m from the laser the beam has a diameter of 1.1 mm. a) What is the average intensity of the laser beam 1.0 m from the laser? b) What is the...

measure of light intensity using a voltmeter? relationship between voltage and light intensity

Homework Statement Instead of sending power by a 850 kV, 1100 A transmission line, one desires to beam this energy via an electromagnetic wave. The beam has uniform intensity within a cross-sectional area of 80 m2. The speed of light is 3×10^8 m/s and the permeability of free space is 4×10^-7...

Why does the stopping potential not depend on the intensity of incident light?

1. A star at a distance of 11 light years from the Earth provides us with a power per unit area of 1.7x10^-12 W m^-2. Calculate the power output of the star. 2. 1ly=9.4608x^15 m therefore 11ly=1.040688x10^17 m 3. How do you work it through? I've never understood these questions...

Intensity and Superposition of waves... Homework Statement Incident wave y=Asin(ax + bt + pi/2) is reflected by an obstacle at x=0 which reudces intensity of reflected wave by 36%. Due to superposition a resulting wave consist of standing wave and traveling wave given by y= -1.6 sinax.sinbt +...

Homework Statement A uniform line charge of -4π x 8.85 pCm^-1 is situated between the points (-5,0) and (-2,0) m and another such line of positive charge between (2,0) and (5,0) m. A) Find the electric scalar potential V at (1,0) m. B) Find the electric field intensity E at the same...

Homework Statement This is the light intensity on a viewing screen behind a rectangular opening in a screen. Is the shape of the opening (1), (2), or (3)? Homework Equations w=(2λL)/a where w is the width of the central maximum, L is the distance to the viewing screen, and a is...

Hi everyone, I am trying to create a data file that contains the intensity of an LED at a particular distance. For each data segment, the distance from the centre point (red dot on my very amateur paint drawing) is d and the distance from the LED to this purple grid is z. So I calculated that...

Hello everyone, I was lately thinking about how exactly do these two main electrical measures - current intensity and voltage - differ in describing the effects of electricity on human tissue (skin/muscle/brain etc). For example, I know that most of the time there are warnings of high voltages...

Just a general question on the EM spectrum. angle deviation of the light wave as it passes through a prism seems to be inversely related (looks like a 1/x graph) to its wavelength. So my question, why? My guess is that the deflected path is shorter than the undeflected by cos A, where 0...

Hello Forum, An optics question here. I'm using a Xenon continuous arc lamp as a source of broadband light together with a spectrometer for an absorption experiment. However the lamp is too bright and is saturating the spectrometer. Is there a standard way to reduce the...