What is Intensity: Definition and 964 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. P

    What is the Intensity of Seidel Point?

    Hello I have to prove that the intensity of seidel point is equal to ##I_{sp}=\frac{8}{\pi^2} I_o## I didn't get any other information only that there is an integration in this prove. Hope you can help me. It is enough for me if you only give me link or the name of this prove.
  2. 0

    Determining the light intensity in a double convex lens

    Attached is an illustration of an image being demagnified using a double convex lens. I want to determine the intensity of the light (mW/cm2) if I were to put a lux meter at various locations after the convex lens given that the object is at a fixed location. The object is a monochromatic light...
  3. Rumplestiltskin

    What is the Intensity of Light 12m from a Bulb Shining in All Directions?

    Homework Statement The light from a bulb shines equally in all directions. If 20W of light is given off, what will the intensity be 12m from the lamp to 2 significant figures? (Consider the shape of the region illuminated if the light hits this surface after traveling 12m in all directions.)...
  4. F

    Am I wrong, or is my professor? Intensity Question

    Hello everyone, please help me understand this. We were given a conceptual question that says "A sound wave goes from the air into the ocean. Which of the following applies (circle all that apply): a)its intensity increases b) its wavelength decreases c) its frequency increases d)its...
  5. karush

    MHB Sound Intensity & Distance Relationship

    4. Sound intensity is inversely proportional to the square of the distance from the source The further from the source you are, the less intense the sound. Suppose the sound intensity is 20 watts per square meter. (W/m^2) at 8 meters. What is the sound intensity at 4 meters...
  6. T

    Measuring aperture size through Lumen intensity -- Advice.please

    Greetings everyone. I'm working on a project that requires the very accurate measurement of distance varying between 0.500'' and 0.050''. I need to measure the distance within at most 0.010'' tolerance and give the value digitally. The read-rate is once every second. I'm on a very tight budget...
  7. Julian102

    Find magentic field intensity.

    Homework Statement A square with each side of 5 cm in length.Now if 4 parallel wires in each 4A current is flowing were placed on the vertex of the square.How can I find the center of the square of the magnetic strength? Homework Equations I am not sure what equation should be used.If I knew I...
  8. R

    How to calculate light intensity?

    I am calculating the light intensity of Mercury. I was given the average distance from the Sun in AU's which is 0.39. Using the formula (1/(d^2)), I solved for the light intensity relative to Earth which I found to be 6.57. I need to find the light intensity in (w/(m^2))
  9. M

    Interference of light Intensity

    An Interference pattern is produced by light of wavelength 490nm from a distant source incident on two identical parallel slits separated by a distance (between centers) of d=0.630mm. a) If the slits were very narrow what would be the angular position theta1 and theta2 of the first and second...
  10. NihalRi

    Effect of rotating polarizer on intensity of transmitted light

    Homework Statement Plane polarised is incident normally on a polerizer which can rotate in plane perpendicular to light. The intensity of of incident light is 8W[m][/-2] and transmitted intensity is 2W[m][/-2] if polerizer is rotated 90 deg what is the new transmitted intensity Homework...
  11. P

    Find emf and the inner resistor of the battery

    Homework Statement When the resistor is R1, in the circle there is the intensity I1 and when the resistor is R2, the intensity becomes I2.Find emf and the inner resistance.[/B] Homework Equations I=emf/R+r The Attempt at a Solution I1=efm/R1+r I2=efm/R2+r efm is equal I1*(R1+r)=I2(R2+r)...
  12. Julian102

    Electric intensity at orthocenter of a triangle.

    Homework Statement At the vertices of a triangle there are + 5C, -7C, -3C of charge respectively. What is the electric intensity and direction at its orthocentre? Homework Equations Each side of the triangle is 1 mm in length. The Attempt at a Solution [/B] I failed to find the distance of...
  13. J

    Mechanically, what does light intensity mean?

    I am not sure what intensity actually looks like and means for light. Does this mean that ex red photon, that there are more than one photon that are superimposed on each other hitting the same spot?
  14. J

    Radiowaves and potential harm? Intensity?

    I understand that radio waves have very low frequency, which means it is not ionizing as gamma and ultraviolet are, but while browsing the web, it seems that there are mixed point of views on its potential hazard to human health. Hmm, if it is dangerous, why? Does it have to do with intensity...
  15. C

    Electrostatics || A cone charged unifomly, find intensity

    Homework Statement A cone of height H and base radius A is charged with charge Q uniformly distributed in all its volume. Find electrostatic field intensity at the top of the cone. DATA: H, A, Q Homework Equations E=ρ/(4πε0) ∫Ω dΩ/R2) and R is a vector (rr^+zz^) r^ and z^ are versors The...
  16. Schwarzschild90

    Plot Relative Intensity of Function in Maple

    Homework Statement Plot the following function in maple (any graphics software): I_\theta = I_m (cos (\beta))^2 \left( \frac{sin(\alpha)}{\alpha} \right)^2 Homework Equations Range = -20 degrees to 20 degrees \beta = \frac{\pi d}{\lambda} \sin(\theta) \alpha = \frac{\pi a}{\lambda}...
  17. stalin

    Why shadows become dark when light intensity increases?

    I observed following phenomena today: in my room with some lightings, there is a stuff toy placed in front of a wall. The ambient lighting doesn't cause any shadow on the wall currently. Now, I switched ON a torch and pointed it to a stuff toy which was kept in front of a wall and a shadow...
  18. CMATT

    Laser Beam Intensity: Solve W/m², J, & mm | Help Needed

    What is the intensity in W/m² of a laser beam used to burn away cancerous tissue that, when 94.0% absorbed, puts 539 J of energy into a circular spot 2.11 mm in diameter in 4.00 s?? I've tried a couple different equations and I keep getting the answer wrong. This is due tonight, I'm super...
  19. N

    Moving vehicles and Doppler Effect

    Homework Statement Here is the problem: http://faculty.kfupm.edu.sa/PHYS/kuhaili/doppler_problem.htm {Mentor's edit: Here's the text copied from the url: A fire engine moving to the right at 40 m/s sounds its horn ( frequency 500 Hz ) at the two vehicles shown in the figure. The car is...
  20. A

    Determine the intensity profile and fwhm for gaussian beam.

    Homework Statement A beam of wavelength 600 nm has initially an intensity profile of Gaussian shape with a fwhm of 1 mm. Determine the intensity profile and fwhm 10 meter away.Homework Equations FWHM = λ/(2NA√(1 + I/Is)) The Attempt at a Solution [/B] FWHM1 = 1mm = 600 nm/(2NA√(1 + I/Is))...
  21. A

    Luminous intensity: from Volt to Candela/m2

    Homework Statement I use a probe for converting optical power to an electrical current. I need to convert Volt to candela/m2. The sensor, a photodiode, measure the brightness of the monitor leaning the probe on the glass (so there is no distance between the monitor and the sensor). The sensor...
  22. azizlwl

    Electric Field Intensity. Finite sheet of charge.

    problem statement, all variables and given/known data A finite sheet of charge, of density ρ=2x(x2+y2+4)^3/2, lies in the z=0 plane for 0≤x≤2m and 0≤y≤2m.Determine E at (0,0,2)m Ans:(18x10^9)(-16/3ax-4ay+8az) Homework Equations E=kQ/R2 The Attempt at a Solution dE=ρdA / R^2 aR...
  23. marif

    Correlation length from intensity profile

    I want to calculate the correlation length of a rough surface from the intensity profile of diffuse and specular reflectance from that rough surface. By fitting with the Gaussian curve, I calculated FWHM of the intensity profile.Generally it is considered thatcorrelation length = 2/FWHMI also...
  24. T

    STD of Poisson distributed particle intensity

    Homework Statement Say I have a detector that detects alpha-particles of some decay process. Let N be the amount of particles detected and let N be Poisson distributed. If I now define the intensity to be the amount of detected particles per second I = N/t, what would the standard deviation of...
  25. DoobleD

    Constant intensity maxima in double-slit interference ?

    Third question about wave optics in two days, hope it's not too much. When we look at the intensity of light on the screen in a double-slit interference experiment (assuming negligible diffraction), we find something like this : When we look at the intensity of light on screen in a...
  26. M

    Intensity of light through two polarizers

    Homework Statement Unpolarized light of intensitry 3 W/m^2 goes through two polarizing films. Their axes are 60 degrees apart. What is the intensity of light transimitted by the second film Homework Equations ##I_2 = I_1*cos^2 phi## Where I_1 is the intensity of light after going through the...
  27. O

    Location and intensity prediction of wave energy

    Hello forum, Is there any method of knowing the location of source and probably intensity of vibration from afar without sorting to a doppler effect? This is in the same as our auditory sense, when people call us at a distance we could easily approximate how far they are and the volume they speak
  28. I

    How Can I Correctly Calculate the Intensity in a Diffraction Pattern?

    Homework Statement Monochromatic light of wavelength 463 nm from a distant source passes through a slit that is 0.0350 mm wide. In the resulting diffraction pattern, the intensity at the center of the central maximum (θ = 0∘) is 9.20*10-5W/m2 . What is the intensity at a point on the screen...
  29. P

    Finding electric field intensity

    3 point charges q1 q2 & q3 are placed in vacuum as shown. Find electric field intensity at B,if q1=2C,q2=-4C & q3=-2C Homework EquationsThe Attempt at a Solution
  30. rizwanibn

    Coulomb's law and Electric field intensity problem

    I am not getting the answer to this question as shown in the textbook. Please help...! My attempt is in the last attachment. Thanks.!
  31. azizlwl

    Electric Field Outside a Uniformly Charged Spherical Shell

    Homework Statement Show that the electric field E outside a spherical shell of uniform charge density ρs is the same as due to the total charge on the shell located at the centre. Homework Equations Using only Coulomb's Law E=Q/4πε0 ar The Attempt at a Solution If i assumed it as circular...
  32. E

    Why is unpolarized light halved in intensity when polarized?

    I would appreciate if the explanation didn't derive this phenomenon using Malsus' Law exclusively and would go into the horizontal and vertical components of polarized light, and how the blocking of the horizontal components results in a halved intensity...so more of a geometric explanation...
  33. N

    Magnetic field intensity and density

    Hello folks, Can anyone explain to me what is the difference between magnetic field intensity H and magnetic field density B?
  34. H

    Is Pluto's Visible Light Intensity Equal to Earth's?

    Is the visible light on the surface of Pluto equivalent in intensity to what it is on Earth? That is, is 1 lux = 1 lux even though it takes light that much longer to get there from the sun? Or are images of distant objects in the solar system taken with longer exposures?
  35. D

    Calculating Power at source from Intensity at distance R

    Homework Statement An enclosed chamber with sound absorbing walls has a 2.0 m × 1.0 m opening for an outside window. A loudspeaker is located outdoors, 46 m away and facing the window. The intensity level of the sound entering the window space from the loudspeaker is 42 dB. Assume the acoustic...
  36. K

    Intensity and Sound Level question.

    Hello, I only have 1 question left to finish my physics homework, and it has to do with sound and intensity. I am having some trouble figuring out how to solve it. Here is the question: At a distance of 17 km, a 177 Hz horn, assumed to be an isotropic point source, is barely audible. At what...
  37. A

    Light Bulb and Transmitted Intensity?

    Homework Statement You have a light bulb where the filament (in vacuum space) starts to glow. This light hits the glass of the bulb at 90 degrees from distance R and is transmitted through the glass of thickness s into the air, of index of refraction nair. So light travels like this: vacuum...
  38. K

    How Do You Calculate the Intensity of a Star at Different Wavelengths?

    Homework Statement We have a Star with known temperature T, Radius R and distance from us. 1) Say we know the effective temperature ##T_{eff}## and we want to calculate the intensity ##I(λ.T) at λ=5500 A##. 2) Suppose that ##I(λ,T)## is constant over the range of visual band and...
  39. S

    Time averaged intensity, derivation and vector plot

    Homework Statement I'm trying to graph this equation: [/B] I'm trying to use the champ command in scilab to graph this from -π to π on the kx and ky axes. But this requires the x and y components of the vector as arguments. How do I get those components, is there a command for that? There's...
  40. E

    What is the intensity of an electromagnetic radiation?

    How can I compute the intensity of an electromagnetic radiation if I know ##e_x, e_y, e_z, h_x, h_y,## and ##h_z##, where ##e_i## is the electric field component at ##i## and ##h_i## is the magnetic field component, also at ##i##? Thank you in advance.
  41. F

    Sound Intensity: Reduce by 35 dB, Factor Calculation

    Homework Statement If you install special sound-reflecting windows that reduce the sound intensity level by 35.0 dB , by what factor have you reduced the sound intensity? Homework Equations Δβ=10Log(I/I°) The Attempt at a Solution I°=10^-12 I=I°-35 35=10^1.5440680...
  42. Nader AbdlGhani

    Optimizing Current Intensity: Connecting Cells in Series and Parallel

    Homework Statement How can I get the maximum Current Intensity by connecting 72 cells to a 3 Ohm resistor each cell has a potential difference of 1.5 Volt and internal resistance of 1 Ohm Please don't tell me to connect them all in parallel or all in series as in parallel the potential...
  43. Jonski

    Energy Intensity of black coal

    Homework Statement Brown coal, energy content 16 MJ/kg, carbon content 65% by weight, burning in a 30% efficient steam power plant. Homework Equations What is the emissions intensity (kg CO2 emitted/kWh delivered) ? Compare this to Hazelwood which is 1.53 tCO2/Mwh 3. The Attempt at a Solution...
  44. Ebenshap

    Gravitational force formula: mass 2 point sources, intensity like 1?

    I want a better visual model of what Newton's gravitational force formula represents: (G⋅m1⋅m2)/d2 But there are two contradictory things that I'm having trouble reconciling: Multiplying the two masses shows a relationship between the two point sources, but using the area of the sphere to...
  45. UMath1

    Is My Jazz Band Practice Too Loud? Concerns About Sound Intensity

    I recently read about the recommended amount of exposure time to high sound volumes: http://www.dangerousdecibels.org/education/information-center/decibel-exposure-time-guidelines/. Since I am in the Band at school I was somewhat concerned about if the sound intensity would be too much...
  46. F

    Calculate flux from a radiating disk

    Homework Statement Suppose you have a disk of radius r at x=y=z=0 with its normal pointing up along the z-axis. The disk radiates with specific intensity I(\theta) from its upper surface. Imagine the observer plane is at z=Z, where Z is much greater than r. Let I(\theta) = I = constant...
  47. Shailesh Pincha

    Why does the intensity of Bremsstrahlung radiation increase with lower energy?

    http://www.quora.com/Why-is-the-spectrum-of-Bremsstrahlung-radiation-continuous In the above link, it says that "you will count more low-energy events since they are more probable." Which must mean that at lower energy we must get more intense radiation...
  48. toforfiltum

    Diffraction grating that gives max intensity

    Homework Statement Homework Equations dsinθ=nλ IαA2 The Attempt at a Solution I chose D because I thought that D gives the max intensity since the amplitudes superimpose over a smaller area. But the answer is C. I can't see why.
  49. B

    What affects the intensity of different coloured lights?

    Okay, so I have completed a practical where I used a light box and then placed different coloured plastics in front of the light and measured the light intensity of each colour. From the results I found that yellow, orange and violet had the highest intensities, with red and green having the...
  50. T

    Power from Sound: Fans Create 12.56 Watts 1km Away

    Homework Statement Fans at a stadium produce sound that is heard 1km away, the intensity level is 60 dB. How much acoustic power is generated by the fans? Homework Equations B = 10 log (I÷I_0) P=I*A The Attempt at a Solution I= 10^-12*6^10= 10^-6W/m^2 P= 10^-6*4pi*1000^2 =12.56W However...
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