What is Inverse square law: Definition and 104 Discussions

In science, an inverse-square law is any scientific law stating that a specified physical quantity is inversely proportional to the square of the distance from the source of that physical quantity. The fundamental cause for this can be understood as geometric dilution corresponding to point-source radiation into three-dimensional space.
Radar energy expands during both the signal transmission and the reflected return, so the inverse square for both paths means that the radar will receive energy according to the inverse fourth power of the range.
To prevent dilution of energy while propagating a signal, certain methods can be used such as a waveguide, which acts like a canal does for water, or how a gun barrel restricts hot gas expansion to one dimension in order to prevent loss of energy transfer to a bullet.

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  1. N

    Plot a graph to verify the inverse square law and use the graph to estimate ?

    Hi, I know that this is my first post, but please help me! I am having trouble with the following question "The following data was collected from an experiment to measure the gamma ray count-rate at different distances from a sample of cobalt-60 The background count was measured five...
  2. L

    Graph of inverse square law for radiation intensity

    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
  3. fluidistic

    Inverse square law and infinite intensity

    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"...
  4. C

    How to find distance of star using inverse square law

    Homework Statement So i need to calculate the distance of some star the luminosity is 2 Lo and on Earth its seen as .1 Lo Homework Equations I=L/4piR2 F=L/4piR2 The Attempt at a Solution I found two formulas, but not sure what to use. The F is flux density, and I am not sure how I...
  5. L

    The origin of the inverse square law

    Where does the inverse square law of gravitation come from? Is it just inserted by hand into general relativity? Or can it be deduced from just Einstein's postulates that in the nonrelativistic and weak gravity limit, the inverse square law just naturally arises? Any help would be greatly...
  6. E

    Inverse Square Law: What & How to Prove It

    What is the inverse square law and how do you prove it?
  7. J

    What is the force between two point charges when they are touching?

    We all know the equations for inverse square laws, such as force between two masses or between two charged particles. We were told the force is inversely propotional to the distance between the masses or charges, squared. But what would the force equal if the distance between, say two point...
  8. N

    X-radiation inverse square law

    [b]1. If the radiationlevel is 400mGy/hr at 2m from a point radiation source, what will be the radiation level at 6m [b]2. I figured that if the radiation was 400mGy/hr at 2m it have been 1600mGy/hr when emmitted from the sorce. [b]3. If the inverse square law works like at 2m...
  9. T

    Why Don't Atom Forces Follow Inverse Square Law? Help Needed!

    Briefly,the forces between two atoms arise from nuclear and electron-cloud repulsions, and nuclear to electron-cloud attraction. But why does the repulsion vary with respect to distance, without following the inverse square law? Should not electrostatic charges follow the inverse square law...
  10. fluidistic

    Understanding Infrared Light Sensors and the Inverse Square Law

    Hi guys. I have a question. See figure 2.1 in the PDF file, page 13. Basically we have a radiation sensor (sensitive only to infrared light) and we have a light bulb in front of it. We must make some measurement to see that the inverse square law holds and so we must measure the "intensity"...
  11. D

    Inverse square law and superposition.

    Hey guys, I'm reading the E&M book from the berkeley physics courses in preparation for my second round of E&M as a junior in undergrad. And they mention some stuff I remember from my intro to E&M class too...namely, that we can use superposition because both gravity and electromagnetism follow...
  12. I

    Inverse Square Law in 1 dimensional space

    Sorry for what could be a rather very stupid question. I'm not an expert in physics nor maths. The inverse square law defines that strength is inversely proportional to the square of the distance from the source. This is justified by working out the surface area of a sphere, which involves a...
  13. D.S.Beyer

    Does time obey the inverse square law?

    We have all seen the graphs of space time. The ones that look like a bowling ball pushed into a bed. But what are those graphs really saying? Are they descriptions of gravitational force? Or simply a visual aid to describe the path that light follows around the body of mass? My question is...
  14. X

    Verification of inverse square law using photocell is straight line

    why the graph for the verification of inverse square law using photocell is straight line instead of a curve ? since intensity is inversely proportional to the distance then graph must be a curve, but why it is straight line ?
  15. S

    How Does the Inverse Square Law Affect Communication with Distant Spacecraft?

    G'day Was just wondering if there are any implications the inverse square law has for the transmission of energy for communicating with spacecraft traveling into the outer regions of the solar system? Thanks
  16. Z

    Question about the brightness of light and the inverse square law.

    Okay, I know that the brightness of light dims by 1 / r^2. I just need a little help about brightness and so forth. What exactly is the unit of brightness ? Also, when using 1 / r^2 Say I am 5 meters away from a light bulb and find the brightness, then I step back 47 meters. Would I just...
  17. H

    Inverse Square Law Homework: Help with #2 Needed

    Homework Statement Can someone help me out with number two please? I'm not sure what exactly it's asking me to do. Homework Equations The Attempt at a Solution
  18. N

    How Does Distance Affect Light Intensity According to the Inverse Square Law?

    Homework Statement A source of light is used to illuminate a screen. 1 m from the source, the intensity of the light falling on the screen is 12 000 lux. Calculate the intensity on the screen at distances of: (a) 2 m (b) 3 m (c) 4 m Homework Equations I 1/I 2 = d^2 2/d^2 1...
  19. O

    Inverse square law with flat detector

    I recently did an experiment to measure the activity of a radioactive source, with the idea that the activity can be found by treating the detector area as part of the surface area of a sphere. In the actual experiment, we plotted u = \frac{n d^2}{\Delta t} against d, where d is the...
  20. M

    Gravitational force, is it inverse square law?

    I may be having a misconecption, please guide me. The force of gravitation between two masses is inverse square law force as depicted by the formula F=G*m1*m2/r'2. Doesn't it mean that this force is one quarter of the origional when the distance between the masses is doubled. Now if a body of...
  21. M

    Inverse Square Law concerning Light

    [a]1. Homework Statement [/b] How does the distance from a point source of light affect the visibility of that light from the said source? Homework Equations This is a bit tricky without sub points, but here goes: I1 x d12=I2 x d22 where: I=intensity d2=distance per sq. unit...
  22. M

    Explaining the Inverse Square Law of Gravity

    Why gravity follows inverse square law? How Einstein explained it? Can someone explain it please?
  23. B

    Using a Geiger–Müller tube to prove inverse square law

    Homework Statement Today our class used a Geiger–Müller tube for the first time, and we conducted a short experiment to prove that Newton's Inverse Square Law also applies to radioactivity. We recorded the number of clicks from a small sample of Strontium-90 for ten seconds at halved...
  24. N

    Inverse Square Law + Special Relativity

    If one assumes that Newtons inverse square law does not act instantly at a distance, and instead obeys the rules of special relativity does it make similar predictions as general relativity? Has anybody worked this out? Maybe the result is similar to maxwell's equations.
  25. T

    Clarification needed on coloumbs law, inverse square law, potential

    I always try and think about the gravatational laws when thinking of the electrical ones: Can I just confirm that Electrical field strength in a uniform field = F/q (force per unit of charge) A electrical field strength at distance r from the body is \frac{-kQ}{r^{2}} where Q is the...
  26. H

    Integrating the inverse square law

    Hi, I am trying to solve the following problem (but note you can skip the details and look at the last equation and help me with the integral): a small planet (mass m) is found at rest relative to the Sun (mass M) with a separation distance x_{0}. Consider now the small planet move in response...
  27. G

    How fundamental is inverse square law?

    A convincing way to reason inverse square law (of classical EM and gravity) is a conservation of the field lines as one proceeds away from a source... http://hyperphysics.phy-astr.gsu.edu/HBASE/forces/isq.html It appears as a reasonable and intuitive thing to expect... but, it does NOT seem...
  28. K

    What are the most precise (hence recent) tests of the inverse square law for gravity?

    Hi guys, I know that in a 2001 paper there were tests of the inverse square law for gravity down to 218\mu metres. But i have seen in other papers (more recent ones) that they claim it has been tested to a greater precision, somewhere around 100\mu metres i think. But these papers only make...
  29. M

    Suppose the gravitation has very very tiny deviation from inverse square law……

    If the gravitation has very very tiny deviation from inverse square law！our solar system became unstable? If so ,how long people on the Earth can notice it? Thank you in advance!
  30. M

    If the gravitation has very very tiny deviation from inverse square law！

    If the gravitation has very very tiny deviation from inverse square law！our solar system became unstable? If so ,how long people on the Earth can notice it?
  31. L

    Very basic Inverse square law problem

    The intensity of solar energy from the sun arriving at the Earth's surface is aproximatly 1400 joules, per square meter, per second. The sun is 1.5 x 10^11m away from earth. At what rate is the sun radiating energy? per meter squared on its surface. The soloution is 1400 = E/(1.5*...
  32. K

    Inverse Square Law and physics

    Hello all, I am currently in Year 11 (Australia), 1st time posting but I really need help, my Physics teacher did not explain how to use the Inverse Square law when dealing with the intensity of light and to make things worse, he would not help me I have a theory why but that is another...
  33. K

    Inverse square law and magnetic fields

    Ok this may be a silly question, but I have trouble grasping the function of the inverse square law and how it relates to the intensity of a magnetic field. It seems to me that if we take the same calculations of I2 = (I1 * D1^2) / D2^2 we come up with different real world answers based on...
  34. C

    Does the Inverse Square Law Apply to Lasers and Perfect Lasers?

    I've read from several sources that says the inverse square law doesn't apply to lasers, but I've been told that it does apply. Which is right? Also if it does apply in today's lasers what about in a perfect laser? Thanks.
  35. A

    How to Solve an Inverse Square Law Problem in Physics?

    Howdy folks, I'm trying to solve a physics problem that I posed to myself one day after a class. My inspiration is a linear particle accelerator. So, what I want to do is model a particle in one dimension, being attracted by an inverse-square-law force. |<---------d-------->| |<--x-->|...
  36. D

    How does the inverse square law apply to electromagnetic radiation?

    Does the inverse square law work for electromagnetic radiation? It should only work if we strictly looks at electromagnetic radiation as 'waves'. But the photon particle isn't a wave, so how would you explain how it works with the photon? I may have misconceptet the photon, but I think that a...
  37. H

    Magnetic potential and inverse square law

    Hi I am in doubt about the lack of the squared distance r in the expression below: v(r)= constant* int_vol div M /|r_0 - r| dV M: magnetization vector r : displacement vectors Is it correct to say that magnetic potential V(r) obeys the inverse square law ? Or it is more correct to say that...
  38. S

    Why is there an inverse square law in electrostatics?

    I have a little doubt. why is there an inverse square law in electrostatics?why not some other than the inverse square? is there any relation/connection between the charges and the inverse square?
  39. M

    Is this inverse square law - help

    is this inverse square law --- help! If the Earth had twice its present radius and twice its present mass, what would happen to your weight? Explain
  40. marcus

    Eot-Wash sub-mm test inverse square law

    Last year the Eot-Wash group found no deviation from invers sq. at close range (on order 100 micron) http://arxiv.org/abs/hep-ph/0405262 Sub-millimeter Tests of the Gravitational Inverse-square Law C.D. Hoyle, D.J. Kapner, B.R. Heckel, E.G. Adelberger, J.H. Gundlach, U. Schmidt, H.E...
  41. M

    How does distance from the sun affect the apparent brightness?

    I have a bit of a hard time with these concepts mathematically and if i can have one person explain it would be a bit lighter on me and i would appreciate the help I just need in steps the way you would go about working this out: Q:the Earth is about 150 million km from the sun, the apparent...
  42. F

    Electric Field: Q, Epsilon 0, and the Inverse Square Law

    electric field is written as q/4*pi*r²*e0. i guess that 1/4*pi*r² stands for the decrement of flux density, with area of sphere (then it looks like force = "flux per unit area"). i need clarification about the constant epsilon 0. I'm not asking definitions such as "it's electrical...
  43. Reshma

    Inverse square law and Kepler's third law

    The inverse square law for gravitation was deduced from Kepler's third law. So how was the inverse square law for electrostatics(Coulomb's law) deduced?
  44. D

    Inverse Square Law - Is It Valid for Quasars?

    I curious about if the invese square law is valid for stars that are very very far away from the earth. like quasars. If the universe was flat and infinite. I could understand that the inverse square law would be valid when looking at objects like quasars, however, if the universe is closed and...
  45. D

    Inverse Square Law: Solving a Question with Door Dimensions

    I had a question regarding a sound with a given Intensity and a given radius (say 0.1m from point source) that travels through a door with dimensions given as well. It also gives a second radius (say 30m from point source) and asks what the acoustic power was at a second radius after traveling...
  46. D

    Solving Sound Intensity with Inverse Square Law & Door Dimensions

    I had a question regarding a sound with a given Intensity and a given radius (say 0.1m from point source) for that intensity that travels through a door with dimensions given as well. It was gives a second radius (say 30m from point source) asking what the acoustic power was at a second radius...
  47. S

    Intensity of laser beam / Inverse square law

    Hello everyone! I'm having a real tough time with this one, maybe I can get a little help. A small helium neon laser emits red visible light with a power of 3.2 mW in a beam that has a diameter of 2.5mm. What is the intensity of the laser beam? Does this intensity obey the inverse square...
  48. J

    Inverse Square Law & Energy Dispersion - Question Explained

    Inverse square law ? Does anyone have an absolute basic understanding of "first order principles of energy dispersion" (A) Energy from a point source disperses spherically at the inverse square law. (B) Energy from an infinite line source disperses cylindrically at ½ inverse square...
  49. J

    Understand First Order Principles of Energy Dispersion

    Inverse square law Does anyone have an absolute basic understanding of "first order principles of energy dispersion" (A) Energy from a point source disperses spherically at the inverse square law. (B) Energy from an infinite line source disperses cylindrically at ½ inverse square...
  50. J

    How Does Energy Disperse from a Finite Line Source?

    Inverse square law Does anyone have an absolute basic understanding of "first order principles of energy dispersion" (A) Energy from a point source disperses spherically at the inverse square law. (B) Energy from an infinite line source disperses cylindrically at ½ inverse...
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