Intensity Definition and 898 Threads

I understand that fluorescence intensity time trace is constantly monitor the fluorescence intensity and plot it over time. But the question is at which excitation wavelength? Also, what is the emitted wavelength that is being measured? I suppose it should be two particular wavelengths, but how...

Homework Statement A sodium lamp emits light at the power P = 130 W and at the wavelength λ = 570 nm, and the emission is uniformly in all directions. (b) At what distance from the lamp will a totally absorbing screen absorb photons at the rate of 1.00 photon /cm^2s? Homework Equations 1...

Homework Statement Two loudspeakers on elevated platforms are at opposite ends of a field. Each broadcasts equally in all directions. At the halfway point, the intensity is 74.1dB. What is the sound intensity level at a point one-quarter of the way from one speaker to the other along the line...

In the photoelectric effect, we observe that the stopping potential is independent of the intensity of the light. This is readily explained by the photon hypothesis. One often sees the statement that in "the classical theory," the stopping potential should increase with intensity. What...

Homework Statement The intensity of a certain spherical wave is 8.0 W/m^2 at a distance of 1.0 m from the source. If the medium is isotropic and nonabsorbing, calculate the decibel intensity 100m from the source. Homework Equations β=10ln(I1/I0) The Attempt at a Solution I know how to use...

Homework Statement A family ice show is held at an enclosed arena. The skaters perform to music with level 80.0 dB. This is too loud for your baby, who yells at 75.0 dB. (a) What total sound intensity engulfs you? Homework Equations I ∝ A2 The Attempt at a Solution Why did the answer sum...

If you take the spectra of a star you usually have a big primary mirror (lets say 1m) to get a lot of light, and use an exposure time usually several tens of minutes. Can one use an astronomical spectrograph for a led/arclamp light source? How does the light intensity of a star compares to...

Homework Statement An electromagnetic wave with frequency 65.0Hz travels in an insulating magnetic material that has dielectric constant 3.64 and relative permeability 5.18 at this frequency. The electric field has amplitude 7.20×10−3V/m. What is the intensity of the wave? Homework Equations...

So I had this idea and I want to run it by some people and see if it's 1) possible 2) worthy of pursuing further 3) a good idea. I don't have a degree in engineering or physics, I'm currently studying chemistry and am taking physics 2 (E&M) right now, so excuse me if I don't use the correct...

I want to calculate the radiation intensity of a cell phone which has a peak output power of about 2.0 W . The formula that I should use is I= P/A right? How to calculate the area if the question only state the distance which is 2 inch from the cell phone?

Homework Statement A Helium laser, λ = 588 nm, shines on double-slits separated by 1.80 mm. An interference pattern is observed on a screen at a distance R from the slits. The point C on the screen is at the center of the principal maximum of the interference pattern. The point P is the point...

I'm searching for a reflexive diffraction grating with at least 1500 line per mm and high intensity in first order. Common reflexive diffraction grating don't have enough intensity for my experiment. I need to help for getting such grating. Thanks

In my book it is stated.When you keep the intensity constant and decrease the wavelength the photoelectric current decreases but I can't understand why? I thought it would stay the same since photoelectric current depends on the intensity of photons as more number oh photons means more e- released

I found that for some LED's manufacturers specify groups/classes of radinat intensity in their datasheets. For example SFH 4258 from Osram http://www.osram-os.com/Graphics/XPic0/00101891_0.pdf/SFH%204258,%20Lead%20%28Pb%29%20Free%20Product%20-%20RoHS%20Compliant.pdf has four groups, going from...

Hey, Could anyone explain why Ia/Ib=2.512^(Mb-Ma), Where "Ia" and "Ib" are intensities of star a and star b and "Mb" and "Ma" are the apparent magnitudes of star A and star B? I thought the formula would be Ia/Ib=(2.512)^(Ma-Mb) because Ia=2.512^Ma and Ib=2.512^Mb. Thank You

Hi, does anyone help me please to convolute atomic data. On x-axis I have wavelength and on Y axis scattered intensity data. Thanks Kartik

Let's say we have the problem: A 100W lamp emits light in all directions. Assuming that the lamp is a point source, calculate the intensity of the radiation 1m away from the lamp. The surface area of a sphere is :4*Pi*r2 intensity = power/cross-sectional area The answer is intensity = 100w/4Pi...

At the moment I'm revising some interference and diffraction basics, and there is something that bothers me slightly and I can't quite figure it out. The intensity of a wave over some area ##dA## is in general is ##I=\frac{1}{dA} \frac{dE}{dt}##. Clearly for an electromagnetic wave falling on a...

http://www.schoolphysics.co.uk/age16-19/Wave%20properties/Wave%20properties/text/Intensity_and_amplitude/index.html well this may be alittle bit simple but in the link above the energy of a physical wave is shown as squared i mean is this done to eliminate that the positive and negative values...

Can someone help me with this question, Calculate the force of gravity on a 70-kg astronaut 2.0 Earth radii from the centre of Earth.

I think basic definition of intensity is power by area. How intensity is square of the amplitude? How intensity is energy density times speed of thing? How in a radiation of EM wave, Half of the intensity is provided by elec.field and other by magnetic field?

Homework Statement A 60 W bulb radiates light uniformly in all directions. What is the average intensity of the light bulb at a distance 0.40 m. Homework Equations I = P/A, part of my problem is that I don't know the relevant equations The Attempt at a Solution

1. In photoelectric experiment, if anode potential w.r.t. cathode is increased, photocurrent first increases then becomes a constant, since all the photoelctorns ejected from cathode are collected at anode. If we increase the intensity of light at this point, the 'saturation current' increases...

GaAs crystal structures have basis atoms: Ga: (0 0 0), (0.5 0.5 0),(0.5 0 0.5),(0 0.5 0.5) As: (0.25 0.25 0.25),(0.75 0.75 0.25),(0.75 0.25 0.75),(0.25 0.75 0.75) i'm trying to find intensities at all of its plane, using this equation: I = (F^2)*m*Lf (m= multiplicity, Lf=lorentz factor)...

I'm still confuse on using the equation about atomic scattering factor, f = a*e^(-b+((sin(theta)/lamda)^2) + c (general equation), where sin(theta)/lamda = 1/2d = 1/(2*(sqrt(a^2/(h^2 + k^2 +l^2)))), so this term is dependent on the plane. which you will used to find the Intensity of crystals...

Hey, Just wanted to thank everyone for their time to help solve people problems, I can generally find all my answers here but I made an account now because i can't seem to find a related problem to this. In general the textbook for these types of problems make the plane z=something. In this...

Homework Statement I really think my answer is correct - could someone verify this or let me know where I went wrong? This is problem submitted online, the "correct" answer looks like my teacher accidentally hit the button 3 twice. PROBLEM: The toriod in example 5-1 from the textbook has an...

This is something that i noticed.i.e., it happen to me, when i went to my teacher to ask him why it happens he actually didn't believe me, i guess maybe because he was a physics teacher! Consider a room with\ all the lights switched off, let their be a far off light source which is very weak...

Homework Statement Which has the most intense sunlight hitting it?Question 2 options: A point on the Equator at sunset The North Pole at Noon on the Summer Solstace Montreal at Noon on the Spring Equinox The South Pole on the (Northern hemisphere) Summer SolstaceHomework Equations none The...

Homework Statement a concrete dam, 20m in height, has a vertical upstream face. if the water level is coincident with the top of the dame, calculate and plot the pressure intensity at 4m intervals over a vertical and thus determine the total hydrostatic force acting per unit width. Show that...

Imagine there is a semi-infinite semi-transparent body--such as a glass--at some temperature T. No surfaces exist. What is the energy intensity of thermally emitted light from any point in the body? If you use an absorption or emission coefficient (as I suspect is correct), can you explain how...

Hi all, I have a problem of understanding the concept of radiant intensity, in particularly I’m interested in LED characteristics and confused with specification in LED datasheet. For example in the datasheeat for the VSMY2850 LED from Vishay it is stated that typical radiant intensity is 100...

When superposing waves in say double slit interference from two slits, I seem to have come across two approaches: 1. Sum the two waves in complex form to get the resultant amplitude, take the real part, and square to get the intensity, i.e I=[Re(A)]2 2. Sum the two waves in complex form to get...

Hello, If we consider a source of light (in a point x), is it wright to say that the intensity decreases in 1/r2 ? Thank you !

I am trying to figure out what the total thermal energy emitted by completely transparent matter. It seems Planck's law can't do this because the thickness or geometry of the mass is not given, only it's surface area. The spectral radiance of a black body is given by Planck's law...

Homework Statement A small source emits sound waves with a power output 80W. a) find the intensity at a point 3.0m from the source. (0.71W/m) b) find the intensity level at the same point as part a.(118.51) c) at what distance would the intensity be one-fourth as much as of that part (a). i...

Hi. Will the amplitude of Poynting's vector change if the electromagnetic wave goes from one medium to another? Shouldn't the amplitude remain constant due to conservation of energy? I.e. the photon-density and velocity will change, but their total intensity remains the same. I could always do...

If we set two speakers far apart, giving identical sound waves having intensity of threshold of pain, in such a way that at midway between them, there is complete destructive interference. Would there any intensity of sound there in complete silence? If not, then where is "lost" intensity gone...

Homework Statement If I measure a sound intensity of 1.0 at distance R from its source, what intensity would I measure at distance 3R in a free, unbounded space? What is the difference in decibels? Homework Equations I know that the equation for this is 10 (log R2/R1) The Attempt at a...

Homework Statement Determine the decibel rating of the following intensities of sound. I = 1.0 x 10-5 W/m2 Homework Equations The equation which relates the intensity of a sound wave to its decibel level is: dB = 10 * log( I / 1.0 x 10-12 W/m2) The Attempt at a Solution dB = 10 * log( 1...

Hi all, My question is, in electromagnetism, magnetic field intensity H is equivalent to electric field intensity E , right?? Now, definition of E says that E is the force experienced by an unit positive charge in an electric field created by a source charge. So what is the definition for...

I understand that intensity is power per unit time and that ##I = 2π^2f^2x^2_oρv## for regular waves (I don't know if the formula applies to E.M. waves or not). What I don't understand is why electrons are only released when the electromagnetic radiation incident on the metal surface is beyond...

Guys, when utilizing the electric field intensity formula ( Fe=qE), do we use the sign of the charge (q)? I think we do, but I remain confused!

Homework Statement Suppose a radiating electric dipole lies along the z axis. Let ##I_1## be the intensity of the radiation at a distance of 10 m and an angle of 90 degrees. Find the intensity (in terms of ##I_1##) at (a) a distance of 30 m and an angle of 90 degrees, (b) a distance of 10 m...

Hello All, I would like to know why do we multiply the complex conjugate of velocity (not just the velocity) with the complex pressure to obtain the complex acoustic intensity. Could someone please help me with this? Regards, Radel...

Can someone assist with a simple model for the following question? I have looked on the net but cannot find anything on it. Say you are sat at a desk with the light bulb directly above you switched off and the rest on; so: on - on - on on - off - on on - on - on Each at distance r apart with...

Hi people not sure if this is feasible but this is the idea and like to hear your comments i wan 2 shine a specific color of light (could be colored LED, normal light,) to determine the wavelength n intensity of it, so i am thinking of using a photodiode and an opamp connected with a...

Homework Statement Coherent light with wavelength 585 nm passes through two very narrow slits that are 0.320 mm apart. The screen is 0.700 m away from the slits. The intensity is I0 at the centre of the central maximum (theta=0) (a) What is the phase difference (in radians) in the light from...

I haven't had calculus in over 2 years and so I am not exactly sure how to go about this. I am inclined to believe some form of integration would be needed. I took the chart below from a paper on LED wavelength emission. The authors say that the vertical line represents the average emission...

Homework Statement A beam of polarized light of intensity 43.0 W/m2 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 degrees for the second...