Inverse Square Law
Inverse Square Law - Related Videos
07:32
Newton's Law of Universal Gravitation
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2023
Source: Ketron Mitchell-Wynne, PhD, Asantha Cooray, PhD, Department of Physics & Astronomy, School of Physical Sciences, University of California, Irvine, CA Legend states that Isaac Newton saw an apple fall from a tree. He noticed the acceleration of the apple and deduced that there must have been a force acting upon the apple. He then surmised that if gravity can act at the top of the tree, it can also act at even larger distances. He observed the motion of the moon and the orbits of the...
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Second Law of Thermodynamics
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2020
In the quest to identify a property that may reliably predict the spontaneity of a process, a promising candidate has been identified: entropy. Processes that involve an increase in entropy of the system (ΔS > 0) are very often spontaneous; however, examples to the contrary are plentiful. By expanding consideration of entropy changes to include the surroundings, a significant conclusion regarding the relation between this property and spontaneity may be reached. In thermodynamic models, the...
11:00
Liquid Phase Reactor: Sucrose Inversion
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2023
Source: Kerry M. Dooley and Michael G. Benton, Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA Both batch and continuous flow reactors are used in catalytic reactions. Packed beds, which use solid catalysts and a continuous flow, are the most common configuration. In the absence of an extensive recycle stream, such packed bed reactors are typically modeled as "plug flow". The other most common continuous reactor is a stirred tank, which is assumed to be perfectly...
03:19
Gas Laws: Boyle's, Gay-Lussac, Charles', Avogadro's, and Ideal Gas Law
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2020
Through experiments, scientists established the mathematical relationships between pairs of variables, such as pressure and temperature, pressure and volume, volume and temperature, and volume and moles, that hold for an ideal gas. Pressure and Temperature: Gay-Lussac’s Law (Amontons’s Law) Imagine filling a rigid container attached to a pressure gauge with gas and then sealing the container so that no gas may escape. If the container is cooled, the gas inside likewise gets colder, and its...
10:12
Newton's Laws of Motion
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2023
Source: Andrew Duffy, PhD, Department of Physics, Boston University, Boston, MA This experiment examines at various situations involving two interacting objects. First, the experiment examines the forces that two objects apply to one another while they collide. The objects are wheeled carts that have variable masses. The purpose of this experiment is to discover when the force the first cart exerts on the other is the same magnitude as the force the second cart exerts back on the first, as well...
FAQs
The key geometric step is that a localized source distributes field lines or emitted energy over a spherical surface. That surface area is 4πr², so increasing the radius enlarges the area available for the same spreading pattern by the square of the radius. The measured intensity therefore falls according to the reciprocal of that area, linking the observed dependence directly to spherical geometry.
Calculate the new value from a reference measurement by multiplying the original intensity by the squared ratio of the reference distance to the new distance: I₂ = I₁(r₁/r₂)². This method supports quantitative modeling because it predicts relative changes without requiring a separate measurement at every position. The distances should represent the source-to-measurement locations consistently.
An ideal inverse-square prediction may not match observations when the source is extended instead of localized, or when the spreading is not isotropic. In those cases, the geometry is not represented by a single spherical point-source model. Researchers should treat deviations as information about source size or directional conditions, rather than automatically as evidence of measurement failure.
Gravity, electrostatic forces, light intensity, and other radiation can all display the same distance dependence when the relevant situation is modeled as spreading from a localized source. The law does not make these phenomena identical; it provides a shared spatial rule for how their intensity or force-related quantity changes with position. This common pattern supports comparisons across physics.
First determine whether the source can be treated as localized and whether the spreading is sufficiently isotropic. Then record a reference intensity and its distance, specify the new source-to-observation distance, and calculate the squared distance ratio. Finally, compare the prediction with the measured value. This workflow separates geometric scaling from discrepancies caused by source conditions.
Light-intensity measurements use the relationship to estimate how illumination changes when an observer or detector moves relative to a localized source. The calculation can guide quantitative predictions at positions where direct measurements are unavailable. If the source is extended or the radiation is not isotropic, however, the result should be interpreted cautiously because the ideal geometric model may not apply.