Intensity Definition and 966 Threads

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 all, Physics was never my strong point at school, yet here I am looking at the differences between three types of graduated light filter for a Health Sciences Masters degree. I'm in the process of writing up, and one of my sets of results is a bit bewildering. Basically, I measured the...

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...

(b) The frequency of sound waves received by a detector when both source and detector move relative to the air is: f=f0[u(+ or -)vd/u(+ or -)vs] . Two trains are approaching each other at a level crossing and blow their whistles at a frequency of 500 Hz. Train 1 is traveling at 20% of the...

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 +...

doing experiment today in which the intensity profile of a filament lamp (of surface temp around 2000K I think) is studied by passing it through a rotating grating apparatus and then reading the output from oscilloscope. My question is why the intensity profile intensity profile the...

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...

Homework Statement Sheet of wire is biased with an electrical potential at each end of conduct current. Given current density, J, in wire: J=-x2y ax +xz ay + 2xyz az A)Continuity equation to prove its possible B) current along length of wire C) Electric field intensity E D) voltage drop...

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...

Homework Statement Hi guys can someone clarify something in my text. I have included a screenshot, and marked the area in question. Shouldnt it be that as the point source approaches you the intensity AND frequency increase? (see the pitfall prevention)...

Homework Statement Two loudspeakers are placed 3.00 m apart. They emit 494-Hz sounds, in phase. A microphone is placed 3.20 m distant from a point midway between the two speakers, where an intensity maximum is recorded. (a) How far must the microphone be moved to the right to find the...

Homework Statement The sound at a concert is measured to be 0.5 W/m^2. How many decibels is this? Homework Equations β = 10ln(I/I_0) I/I_0 = 10^(β/10) The Attempt at a Solution I_0 = 1*10^-12 W/m^2 I = 0.5 W/m^2 Therefore, β = 10ln(0.5/10^-12) β = 269.378 dB However, .5/10^12 = 10^(β/10)...

Homework Statement http://img232.imageshack.us/img232/8514/unbenannthz.png In this system, a single-span beam is exposed to the following stresses: \sigma_{max}= 255 Mpa at F_{max} = 50 kN and \sigma_{min}= 102 MPa at F_{min} = 20 kN The stress range is accordingly \Delta\sigma = 153 MPa...

Homework Statement Monochromatic light of wavelength 620nm is going through a very narrow gap through the first curtain,then encounters a second curtain that is parallel with the first in which there are two parallel narrow slits S1 and S2 as shown in Fig. Slit S1 is located at the point of...

A light source has uniform intensity I(with respect to wavelength) within a circle of diameter 3 arcmin on the sky. The flux of radiation reaching the observer is 10^(−16) erg cm^(−2) s^(−1). Calculate the intensity of the light from this source. Relevent Equations: This is where my...

Homework Statement How much greater than the intensity of a 1 dB sound is the intensity of a: 2dB sound? 3dB sound? 4dB sound? Homework Equations 10pW/m^2 = 10 dB The Attempt at a Solution Hey guys, this question doesn't have an answer in my textbook i think you have multiply...

so I am testing out different designs on a nitrogen laser, and wanted a quick way to test whether or not one design had a more intense output than the other. without having to buy a sensor, my idea was to direct the beam onto a solar cell, then measure the output current. higher current wud mean...

pretty straightforward question. for a long time I've been blindly calculating that intensity is (displacement from zero)^2, but never questioned why. So why is this? I get that by squaring you get a positive value, which helps in, say, quantum probability calculations, but what's wrong with...

Homework Statement I was stuck on a question today in my Optics exam (I didn't have time to think well about it but I'm still stuck). The problem was more or less like this: There's an incident linearly polarized light in the direction of \hat x; we want to polarize it so that we get \hat E =...

Which one do you think does a sound wave travel faster ?How can I experiment on this? Thanks :)

Homework Statement [PLAIN]http://img714.imageshack.us/img714/8205/65617184.jpg Homework Equations I = I_{0} [\frac{sin[\pi a(sin\theta)/\lambda]}{\pi a(sin\theta)/\lambda}]^{2} The Attempt at a Solution Here is my attempt: I = I_{0} [\frac{sin[\pi (50)(sin\1)/632]}{\pi...

Homework Statement what is the gravitational field intensity at the center of the earth Homework Equations The Attempt at a Solution i was told that it was zero because you have the Earth's mass surrounding it, and graivty moves to the center of its mass (center of radius)...