What is Intensity: Definition and 963 Discussions

Sound intensity, also known as acoustic intensity, is defined as the power carried by sound waves per unit area in a direction perpendicular to that area. The SI unit of intensity, which includes sound intensity, is the watt per square meter (W/m2). One application is the noise measurement of sound intensity in the air at a listener's location as a sound energy quantity.Sound intensity is not the same physical quantity as sound pressure. Human hearing is sensitive to sound pressure which is related to sound intensity. In consumer audio electronics, the level differences are called "intensity" differences, but sound intensity is a specifically defined quantity and cannot be sensed by a simple microphone.
Sound intensity level is a logarithmic expression of sound intensity relative to a reference intensity.

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  1. M

    Intensity as light passes through two quarter-wave plates?

    I have unpolarized light passing through a polarizator assuming the angle 0°. The polarized light then passes through two quarter-wave plates, the first one with the angle of 45° (maximum intensity) and the other one. Then it passes through a last polarizator having an orientation perpendicular...
  2. EF17xx

    Single/double slit diffraction intensity

    Homework Statement SINGLE SLIT Why does the intensity at maxima decrease further away from the central maxima in a single slit diffraction. DOUBLE SLIT Slit width: Why is the intensity of a double slit interference pattern the same at each maxima. (constructive interference) When the slit...
  3. TheBigDig

    Find the time dependent magnetic field intensity

    Homework Statement Calculate the time-dependent magnetic field intensity B(t) at an axial distance r from a long, thin straight copper wire that carries a sinusoidal current with an alternating frequency of 50 Hz and a maximum amplitude of 0.5 A. Homework Equations I = Asin(\omega t) B =...
  4. Sheldon11

    B Interference pattern intensity

    why the intensity is the most in the center in interference pattern?
  5. PKM

    What should be the electric field intensity inside a sphere

    If the force acting between two point charges were proportional to \frac{1}{r^ 3}, instead of \frac{1}{r^ 2}, what would be the electric field intensity and charge density inside a charged solid metallic sphere?
  6. T

    Finding minimum and maximum intensity of waves

    Homework Statement Two loudspeakers are placed 3.00 m apart horizontally.They emit 425 Hz sounds, in phase. A microphone is placed d= 3.20 mid 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...
  7. A

    Intensity for Young’s Double Slit Interference

    Homework Statement Hi The experimental setup involved a helium neon laser of wavelength 670nm +- 1nm, pointed towards a lens with focal length 500mm +- 1mm. (so that the equations used corresponded to the far field diffraction pattern) and onto a photo diode so that for all intents and...
  8. bluejay27

    A What form of the Schrodinger equation do you use for intensity?

    I am trying to see how I can use the schrodinger equation to quantify the changes in the intensity of light. My closest guess is using the time dependent pertubation theory
  9. G

    Find ##2\theta## Values from Rotated Crystal and Intensity

    Homework Statement Consider the crystal in the attached image (https://ibb.co/ftMrBH) (a triangular lattice of white atoms with a triangular basis of grey atoms attached to them at angles of 0, 60 and 120. From a previous problem the fractional coordinates of the atoms in the basis are (0,0)...
  10. G

    Electron Diffraction Intensity and Reciprocal Lattic

    Homework Statement Low-energy electron diffraction (LEED) experiments are carried on to study a deposition of argon (Ar) and xenon (Xe) on the surface of a graphite single crystal. In the regime of vapor pressure considered, 75% of Ar and 25% of Xe are adsorbed on the (hexagonal) crystalline...
  11. S

    Approximating nxnx(m-1)+1 Overall Intensity Levels

    Homework Statement PROBLEM STATEMENT: Show that with an n × n pixel grid, where each pixel can take on m intensity levels, we can approximate n × n ×(m – 1) + 1 overall intensity levels. TEXTBOOK'S SOLUTION TO THE PROBLEM: Since the n ×n pixels can be set to a non-zero intensity value one...
  12. N

    Sound Intensity Propagation and Sound Waves

    Hello everyone, I'd ask you through an illustration which for me would be more clear to put questions I wrote in the image: Thanks to all! Cheers Luigi
  13. P

    Calculate the intensity of the Earth's magnetic field

    Homework Statement a circular coil of radius 120 mm with 10 turns is placed with its plane parallel to the Earth magnetic field . when a current of 0.45 A flows through the coil , a compass needle placed at the centre of the coil is seen to be deflected by an angle of 45 degree to the plane of...
  14. J

    Electric field intensity at a distance

    Homework Statement Homework EquationsThe Attempt at a Solution The radiations from the bulb spread radially outwards such that "Power at a distance r" = Power radiated/4πr2 . If distance is unchanged and power halved then the intensity should also be halved . From this I get E' = E/2 ...
  15. N

    About acoustics physics -- The Wave Equation and diminishing sound intensity

    Hello everyone! :-) Actually I'm starting to understand acoustics physics and I figured actually out about this equation: $$\frac{\partial^2\psi}{\partial t^2}=c^2 \nabla^2 \psi$$ which describes practically about pressure and propagation speed into space and time. I know also this equation...
  16. M

    How to calculate the intensity of light, given area and mass

    Homework Statement You want to support a sheet of fireproof paper horizontally, using only a vertical upward beam of light spread uniformly over the sheet. There is no other light on this paper. The sheet measures 20.8 cm by 28.8 cm and has a mass of 1.70 g . (a) If the paper is black and...
  17. T

    I Laue Diffraction Intensity Distribution

    I am trying to experimentally determine the atomic scattering factors for NaCl using Laue photography. For an NaCl crystal, the intensity of the wave scattered at the unit cell is proportional to (4⋅(fCl+fNa))2 if h,k,l are even and to (4⋅(fCl-fNa))2 if h,k,l are odd. fNa and fCl are the atomic...
  18. shaf777

    Spectrum Intensity of Light

    Homework Statement I have an equation to solve. See the attach pichture. I(r,φ,λ) = I0.sin(2πr/R).sin2(φ).(1/λ) where I0 , R are constants r,φ are cylindrical coordinates 0≤r≤R/2 : the cut is laterally limited λa ≤ λ ≤ λb : the beam contains a limited frequency spektrum where the shortcut for...
  19. S

    I Plotting a far-field Intensity distribution

    Hey, I'm attempting to plot a far-field intensity distribution using theoretical values, however I'm having difficulty with calculating the intensity using the following equation: $$I = I_o \frac {sin^{2}{b}}{b^{2}} \frac {sin^{2}{Ny}}{sin^{2}{y}}$$ where: $$y = \frac {kdX}{2f}$$ $$b =...
  20. S

    Fraunhofer diffraction experiment- neural density filters

    I'm currently carrying out an experiment with Fraunhofer diffraction. It involves shining a laser beam through neural density filters, a lens and a diffraction grating, to create a diffraction pattern which is then picked up with a CCD camera, to find the intensity of the maximal peaks. However...
  21. T

    Understanding Gauss' law: diff b/w E and D flux?

    I noticed the other day something odd in how we use Electric and Magnetic flux. The definitions I refer to are magnetic flux density (B), magnetic flux intensity (H), electric displacement field (D) or Electric field density (D) and electric field (E): B = μH ΦB = B*Area & D = εE ΦE = E*Area...
  22. Y

    I Why does intensity mean anything if there's a complex number

    So say a wave is described by Acos(Φ), completely real. Then the to use Euler's Eq, we we say the wave is AeiΦ, which is expanded to Acos(Φ) + iAsin(Φ). We tell ourselves that we just ignore the imaginary part and only keep the real part. And if intensity is |AeiΦ|2, which is (Acos(Φ) +...
  23. Cocoleia

    How does reflection affect the intensity of the microwave?

    Homework Statement I am working on a lab report, and I am a bit stumped at these questions: How does reflection affect the intensity of the microwave? Is all the energy of the wave striking the Reflector reflected? Does the intensity of the reflected signal vary with the angle of incidence...
  24. K_Physics

    Relative Intensity of Various Light Sources - Lab Experiment

    Homework Statement I've linked my data table down below. My problem is the relative intensity column. From the table, the units of relative intensity are w/m/s. I'm assuming this is power/velocity, where velocity is the speed of light. However, nowhere in the lab manual did it mention the...
  25. B

    Decibel Intensity level question

    1. A jackhammer produces a sound of 111 dB IL. What is the sound level when 8 jackhammers are operating simultaneously? When 100 jackhammers are operating simultaneously? When 400 jackhammers are operating simultaneously?2. 1 jackhammer = 111 dBIL, 2 jackhammers = 114 dbIL, 4 jackhammers =...
  26. Z

    Photoelectric Effect, Light Intensity and Stopping Voltage

    In a physics investigation we were required to use a Photo-Electric Effect Instrument (Shown in the attached pdf file), which was able to measure the current produced via the photoelectric effect. One of the objectives of the investigation was to alter the aperture size, and hence intensity of...
  27. E

    Electric Field Intensity of a line on bisecting plane

    Homework Statement A very thin, finite, and uniformly charged line of length 10 m carries a charge of 10 µC/m. Calculate the electric field intensity in a plane bisecting the line at ρ = 5 m. Homework EquationsThe Attempt at a Solution Not sure why I'm not getiting this but I've been at this...
  28. E

    Which formulas are appropriate for calculating intensity?

    Homework Statement Monochromatic plane waves of wavelength 537nm are incident on two narrow slits and produce an interference pattern on a wall 3.1m away. The slits are spaced 26 micrometers apart and are 5.7 micrometers wide each. What is the ratio of intensity to that of the central fringe a...
  29. H

    Question about Intensity in an Interference Pattern

    Homework Statement Two slits spaced d 0.0720 mm apart are 0.800 m from a screen. Coherent light of wavelength λ passes through the two slits. In their interference pattern on the screen, the distance from the center of the central maximum to the first minimum is 3.00 mm. The intensity at the...
  30. Const@ntine

    Sound Intensity (Level) - Hearing Aid

    Homework Statement A man is wearing a hearing aid device that increases the frequency of the sounds the human ear can conceive, by 30 db. The device "catches" a sound of frequency f = 50 Hz, and intensity I = 3.00 * 10-11 W/m2. What's the intensity that the man's ear hears? Homework...
  31. S

    I Neutrino Production by Sun: Heep's Intensity & Branching Ratios

    Sun produces neutrinos by sundry reactions: p+p→d+e++νe - called "pp" p+p+e→d+νe - called "pep" 3He+p→α+e++νe - called "hep" 3He+p+e→α+νe - never mentioned. What should it be called? "Heep"? Now, heep neutrinos should form a sharp line at a quite high energy. What is the intensity of heep line...
  32. T

    Polarization between 3 sheets intensity

    Homework Statement Hi guys I am having a problem with this question Q55 a) and b) My problem is that for part a) I used the following logic. That if two sheet won't let light through at ##90^\circ## so if a 3rd sheet is inserted between the two the angle between each is ##45^\circ##, But...
  33. Tulio Cesar

    Relation between sound intensity and frequency

    The sound intensity formula is given by: dE/dT*dS. So the variables are energy, related to the amplitude of the wave, area, related to wavefronts distribution on space, and time. So many times I don't see any reference about the relation between frequency and sound intensity, but if time is a...
  34. C

    Intensity after Laser Round Trip

    Homework Statement Im having trouble understanding where the value of 0.95 came from which takes into account mirror losses. 1 Flat mirror, So no given reflection coefficients as system has no curved mirrors. Given that the distributed cavity Loss coefficient is 10^-4 and the signal gain...
  35. R

    Selective Incident Headlight Intensity Measurement

    Hey guys, I am trying to come up with an idea to measure incident intensity of headlights from an oncoming car for one of my uni projects. This wasn't specifically assigned project topic, we get to choose what we want to do. It's my Instrument and Measurement unit, and I had this idea thought it...
  36. P

    B Does the Compton effect only occur at a specific angle of incidence?

    Why is there a peak in intensity at the initial wavelenght? Does this mean thst there are photons reaching the relevator without being scattered? How? Do they hit the electrons? I put a photo of the graph
  37. sergiokapone

    Intensity of p-polarized light through stack of plates

    As one know, the intensity Fresnel equations for the reflected p-polarized light \begin{equation}\label{a} \frac{I_{p_{refl}}}{I_{0p}}=\frac {\tan^{2}(i-r)}{{\tan^{2}(i+r)}} \end{equation} and for the refracted one is \begin{equation}\label{b} \frac{I_{p_{refr}}}{I_{0p}}=1 - \frac...
  38. oobgular

    Far IR light intensity as a function of altitude

    Homework Statement Hello, so I'm in a class that is building sensors and sending them up in a weather balloon. For my project, I am wanting to quantify the greenhouse effect by measuring the intensity of infrared light emitted as thermal radiation from the Earth as a function of height-- the...
  39. SunThief

    I Off-angle irradiance from Radiant Intensity

    For a light source with a given radiant intensity, I'm confused about the calculation of irradiance at off-angles. I've uploaded a drawing that shows a few spots and their location relative to the source, along with what I understand to be standard calculations. Then at the bottom of the...
  40. Asmaa Mohammad

    The intensity of x-rays in a Coolidge tube

    Hi, I would like to understand the factors influencing the intensity of x-rays in Coolidge tube. One factor would be the intensity of current in the tube, e.g., the number of electrons emitted by the cathode (the filament), I have no problem with that factor. But I read that another factor is...
  41. Conductivity

    Effect of frequency and intensity on PE

    if two light with different frequency have the same intensity then the PE current is the same. But that doesn't make sense, and some graphs show that if you increase frequency while intensity is constant, the current increases up to a point then drops. A couple of old threads, people mentioned...
  42. C

    What is the relationship between solar radiation intensity and lunar phases?

    Homework Statement What is the intensity of solar radiation in a place where is the full moon ? I know luminosity of the Sun and Earth's distance from the Sun RE and Moon´s distance from the Earth RM. Trajectory of Earth and Moon are circular. Homework Equations distance of the site from the...
  43. I

    Intensity of light passing through 3 polarizers

    Homework Statement Three polarizing disks whose planes are parallel and centered on common axis. The directions of their transmission axes relative to the vertical are respectively: θ1 = 33° clockwise, θ2 = 21° counter-clockwise, and θ3 = 25° clockwise. A beam of light polarized along the...
  44. Ian Baughman

    Calculating Sound Intensity and Pressure Variation at a Distance

    Homework Statement A speaker blares out music with a power of 10 W. Assuming the air has a temperature of 50°F and a pressure of 1 atm, what is the sound intensity level in decibels at a distance of 100m away? What is the maximum pressure variation at that point? What is the distance at which...
  45. Samama Fahim

    Spectral Intensity as a Function of Wavelength in Blackbody Radiation

    A blackbody is also a perfect emitter giving off electromagnetic waves at all frequencies. A detector could measure the intensity of the radiation it receives through the prism. By moving the detector to different positions, you could measure the intensity of light as a function of color or...
  46. Cocoleia

    Electric field intensity on thin electric sheets

    Homework Statement Homework Equations The only equations I can think to use would be: But I'm not sure if they are useful or how they will help. The Attempt at a Solution I have the solution, it just isn't detailed... I don't understand where they get E=1/2ε. Should I be considering...
  47. P

    What happens to intensity during light interference?

    Dear Every Smart Person, I am not a scientist or a physicist by any means, but I have a concept that has been literally driving me crazy all day. No matter how much I read, I can't make sense of it. Here it goes. I work in the LED Lighting space. In that space, there are two types of LEDs: a...
  48. K_Physics

    Loudspeaker Question (Sound and Intensity)

    Homework Statement Suppose a spherical loudspeaker emits sound isotropically at 10 W into a room with completely absorbent walls, floor, and ceiling (an anechoic chamber). (a) What is the intensity of the sound at distance d = 3.0 m from the center of the source? (b) What is the ratio of the...
  49. Arup Biswas

    Why subsidary maximum has lower intensity physically in single-slit diffraction?

    In single slit diffraction the subsidary maximum has lower intensity than of central. Yes mathematically from the intensity equation we can see that. But how physically we can explain that? When the central and the 1st maxima has same activity to produce constructive interference( as in same...
  50. J

    Explaining Light intensity with EM Field Oscillations?

    I have understood that the frequency of an EM wave is caused by the frequency by which a charged particle oscillates, which causes its electrical field to periodically change its strength with respect to a fixed location point at a distance from that particle. The more energy (heat) you add to...
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