Physics 8.1.03a - The Inverse Square Law
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- čas přidán 1. 09. 2009
- The nature of an inverse square law, and how it arises naturally as a property of three dimensional space. Newton understood geometrically that light dispersed according to an inverse square law and surmised, correctly, that gravitational force would be described in a similar manner. From the Physics course by Derek Owens.
my physics teacher refused to explain this, thank you
He studied physics for the sake of some external reasons. He cant understand the subject
@Johnny Street Sign it destroys what certainly?
@Johnny Street Sign respect that!
@Frederic Reeber dang! Took about 1 year but it finally worked and now I am jobless I thank Instapwn for helping me so much
You explained this concept quite thoroughly. Im a senior student and was trying to understand as to why it was an inverse square relationship for the force of gravity. And not just an inverse relationship. This video explained it beautifully. Thank you so much!
Also known to Michael Reeves as "Light get more dim, when it more farther away" 🤣
I wish all youtube was like this. Straight forward explanation and demonstration. In fact, I wish the whole internet or life itself was like this. We could learn so much rather than constantly digging through all the bull.
For gravity, it is F = (G m1 m2) / r^2.
For other inverse square relationships there are different equations, but they all have a similar form, that is, they all have a variable squared in the deonominator.
Here after more than 14 years and will take this knowledge with me till the day my cognitive abilities leave me .
Sir, you are a saviour. A 10/10 explanation with a cookie bonus, THANKS
Thank you for this video. Taking basic Astronomy and had trouble wrapping my head around this concept!
Great explanation. I've been looking for something like this to use in my college photography classes to show the relationship between light distance & exposure. This is it.
Bravo!
I love how this is analogous to graph transformation. It creates a new way to view graph transforms
Thank you!! I knew I could understand it but I’ve not had it explained so clearly before.
I'm watching this 10 years later 🙃
And the concepts are still true! That's one of the things I like about physics.
Wow you still reply even after 10 years.
@@user-zs1gd3vz1l And I hope to still be here 10 years from now, or more.
@@derekowens how old are you?
@@nivasraj5599 I was born in 1966.
A video with an actual clear explanation. Great video
Thank you, I’m using this for large format photography ratios of reciprocity exposure. This was awesome.
I understood everything, loved this. God I wish I had a teacher like you !!
You have a great way of explaining and it’s really entertaining 👏❤️
11 years later and it’s still true. Thank you for making this video this makes learning physics online so much easier
This video has given me such a better understanding of the entire concept. Thankyou very much!!!
THANK YOU! Perfect explanation that I have wondered about since High School and I'm 40!
im50
Thank you sir, very clear & to the point.
Awesome, thank you for your help. Videos like this, from people like you, are an enormous help to us students. I`m sending you a good karma payment.
Suprisingly simple concept for such a complex name
The first time I watched this I didn't realise my speakers were turned off, I just thought it was a visual only video. It was excrutiating, and a bit baffling, except that I could see the geometry at play. Made much more sense with the audio on though hahaha. Duh
Thats creepy to imagine idk why xD a bit eerie
What a great explanation! .. you sir are awesome .. thanks.
Thank you for the demonstration.
This was great thank you :) explained things very nicely
@Akileze Yes, Coulomb's Law is also an example of an inverse square law. The equations for electric charge have many similarities to the equations for gravity.
oh man thank you, this explanation is amazing.
@derekowens Thank you for your time sir and good sailing/safe passage!
Thank you very much for your explanation.
nice, simple, interesting
truly a great job
Awesome, it totally makes sense! Thanks.
Great job
this video helped me a lot
Thanks for the lesson
Excellent explanation 👌
@metalupyourass9 Yes, I think you have the right idea. At 3 meters, you have 1/4 the light intensity that you have at 1.5 meters. Increasing the distance by a factor of 2 will cut the intensity to 1/4. And yes, if you start at 1 meter, then the squares you are imagining are smaller than if you start at 1.5 meters. At 3m, you will have 1/9 the light that you have at 1m, and 1/4 the light you have at 1.5m.
Thanks. I am reading about Newton for my own pleasure, and I am up to the point where he and Hooke argue about whether Newton plagiarizes Hookes "inverse squares" theory. Thank you for telling me what they were arguing about.
Where do you read
I understand this concept as a proportion of brightness to distance in regard to diffused reflected light but am struggling to understand how to apply it to direct reflected light since in this scenario brightness is constant. With direct reflection wouldn't it be a proportion of distance to surface area that the light fills?
Man i am in sixth grade and i understood this you are a great teacher
***** Wow, well aren't you a wet blanket...
+Gabe Holmes how is 7th grade?
how's 8th grade?
how is highschool?
Excellent video
Thanks for the refresher
Based on the inverse square law wouldn’t the moon be so incredibly bright where it would be impossible to actually get anywhere remotely close to it based on what they say the distance is?
I think there are two things to consider here: The inverse square law assumes the light comes from a point source, which would be the center point. When you are far away from the moon, this assumption is valid. When you are close to the moon, it is much less like a single point. Second, the light is reflected off the surface. When you are close to the moon, you are only seeing a small portion of that surface.
Thank you so much sir..
Very Good Teacher.
TY for the visual. For those of us that are less math inclined, how much less would a light source be for something 237,000 miles away like the moon please?
Knowledge is awesome.
I mean to say if I have a torch and point it at say grease proof paper at 3 mtrs away I will still get RADIATION expessing itself in a cone so a circle on the paper and HOW do we understand the formula for this....or is it squaring the circle?????
In a RFID system, with a reader and tag, where the distance between them is 0.04 m. how to apply this concept ? Thanks in advance for your help......
@bomberfun1 you would have to take into account that light is absorbed and reflected off the air particles.
My class have to watch this video because our teacher can't explain it because of CORONA VIRUS
yeet
@@jensen6647 😂
Thank you!!
I understand that the inverse square law says if you double the distance between the light source and the screen, the screen receives a quarter of the the light, how does cutting the distance in half between the light source and the screen make the screen receive only double the light?
Going from 1 to 2 meters, the screen receives a quarter of the light it received from 1 meter,
But if you were to go 2 to 1, the screen receives only double the light that it had from 2 meters?
The math in my head doesn't make sense, I don't know where I'm going wrong. Does anyone know where I'm going wrong?
thanks, really helped.
i just wanted to know the inverse square law applicable for gravity u r a born teacher thanxxx for helping me out
awesome... good job, good video. easy to understand.
do sound waves follow the inverse square law too?
Great video
Excellent explanation. Teach me calculus.
Can you help me? what if I took reading using a solar cell at regular intervals of 5mm. When i conducted the experiment when the solar cell came into contact(0cm) the reading was 10.35 milli amps but when i moved 5mm away the reading was 2.7 milli amps. 10mm after that the reading was1.15 milli amps. so here the inverse square law is quite disproportionate. please help me explain and understand it?
Q..... so please explain how we are meant to understand what happens say at 3m squared (9 squared meters) not sure which way round to say that? but how are those 9 squares meant to be distributed around an X and Y since potential mangetic and or electric has these values as it occupies 3D space.... cheers buddy
Thank you. Is the inverse square law also valid for communication/radio signals over vast distances in a vacuum? What remains of a radio signal after it traveling 240,000 miles to the moon?... or 34M miles from the earth to mars?
Yes, that's correct. The strength of the signal decreases over distance according to an inverse square law. A dish antenna can focus the signal and can compensate for that, sometimes very effectively, but if the signal is propagating from a point source, through 3 dimensional space, then the inverse square law should apply.
what about laser beams which are minimally divergent or parallel rays? ...just a thought
Please tell me if i'm correct or not, but the equation would be...
Area Units = Units of Length Away^2
Thank you. Astronomy homework solved!
@Akileze I don't work in this area, although it is certainly fascinating. I mainly teach physics and math. I've heard some chatter about these ideas lately. I don't know enough to comment on it intelligently, but it is certainly very interesting.
Just a minor addition... It was Robert Hooke that mentioned to Newton about Inverse Square Law application to Gravity. Newton never gave him the credit due to a previous conflict regarding the origin of colour.
how does this relate to coulombs constant?
So helpful, thank you ;-;
1. Why did the lines of symmetry and rotation break as z increased?
2. Why did you use a rectangle which has an additional inverted symmetry with 4 rotations?
3. Why not start with a circle or triangle, which both have one symmety and infinite or zero rotations, respectively, that add complexity but are ignorable?
4. Why, at 3dz, did the expansion of 1 to 4, not go to 16?
Edit: two inversions for a sheet. 0 or 1 for rotations.
Edit 2: the proposed 4 symmetries for squares, should really only be two because, rotation does the remainder; I.e. a rotation for every symmetry. So, 1/8th gets closer to the third pinch point.
@derekowens Do you do any work/research in the area of Particle Physics? There's some data from Cern and Gran Sasso claiming they have clocked neutrinos traveling faster than light. This is a remarkable claim considering the difference is in the realm of 10^-9 on a result expected in the order of 10^-3. Nanoseconds of difference on a millisecond result is noise in my mind.
Sorry to wander off topic but it's loosely related .. I think ;-)
Thanks Again!
The sum of the light hitting the 3x3 screen will be the same as the sum of the light hitting the original 1x1 screen.
This must mean that each square in the 3x3 screen gets only 1/9th of the light.
Since each small square will be less bright the whole screen must appear less bright.
Thank you
Light get more dim when more farther away
Don't understand it, how is the light gets more dim if it's supposed to light
Does the Inverse Square Law explain the Fermi Paradox? Radio waves are ballistic, too...
I have a question, which is the only thing about this i dont quite understand. do u have to start at one metre? what if you start at 1.5, double that and at 3 metres away you have 4x the size (1/4 the light). but at that same point. (if you started ay 1 metre away) you would have 9x the original. or would that just be because your squares are smaller then, starting closer
Does this explain the Fermi Paradox? Other people are "out there", but their radio signals are too faint to hear by the time they reach Earth-based radio telescopes...
Good explanation of light, just know gravity has never been proven.
Watching this during pandemic
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Keep trying. You can learn to like it. Kind of like coffee.
May I know to which comment are you responding this to ?
@@naveensundar4765 necroooooooo
@@aquaexnar3093 not really a thing in yt
@@gonzilo436 bro a necro is a necro, no matter where it is. dont respond to a 7 year old post
How does this work in space?
Yes, I believe they do. Anything that propagates in three dimensions should follow an inverse square law.
My question is that, E=lm/m2.but. E=I(luminous insity)/m2 according to laws of illumination.please clear my doubt
Yeah, but what is a flashlight?
What is the mathmatical equation?
Just like TV and radio transmissions emitting out into space.
So the light would at some point become invisible to the naked eye but would never petter out and go on forever? So essentially in space time nothing ever really dies. It just becomes invisible or inaudible. Therefor our actions go on forever. If you were to able to move into the 5th dimension you would be a able to experience not only the event of the light going out into space but also all possible events of the light going out into space. If you were in the 4th dimension you would be able to see the light at every point in space/time simultaneously as one event. InnerSteller was a great physics lession for us non academics
As absurd as it sounds. Could another analogy be if a flashlight were to be powering the "light" with the Sun's UV ray somehow. Meaning that basically the flashlight contains the actual Sun. The distance of it after expanding towards the screens could be thought as Solar panels. As the closest one would most likely get the most energy and as it extends the energy decreases?
can u explain the kinetic theory of gases like this video
Kinetic molecular theory is chemistry.
thank u sir
Ok so I’m struggling with this thinking about how we’re able to see stars. It doesn’t make sense to me
Thanku
great......
Thanks
So thanks
Why not Electromagnetic force ?
Great presentation. I have only 1 question. Would the Inverse Square law ever arrive at a 0 value. Meaning, given your illumination example, would there ever be a distance when, mathematically, the distant screen received 0 light?
Mathematically, it would never get to zero, no matter how large the distance. In practice, at some distance the force would be too small to measure and at that point would probably be considered zero for practical purposes.
@@derekowens thats what thought.. I just needed to hear it from someone who knows it better!! Thanks
Huh no math required awesome. Finally understand this inversed square law. Really hate mathematicians naming convention. Makes it more complicated/.
you rock!
Does this apply to space? And light with distances so massive.
Yes, it certainly does. You can think about the amount of light per square meter landing on earth and compare that the light per square meter landing on Mars, farther away. And on out to the more distant planets and beyond.
why is it that the first increment to the 2nd becomes double the width, but to the third it is just 50% wider? so why is it not 16 cubes at 3 meters?
I'll try to explain. Each individual light ray is perfectly straight. So as they spread out, their distance increases at a steady rate. So the width isn't doubling each time (1, 2, 4, 8) but instead the width is regularly increasing (1, 2, 3, 4). The inverse *square* part occurs because both the width and the height are increasing in this linear fashion: 1, 2, 3, 4, .... And since the area is the width times the height, the area increases like this: 1², 2², 3², 4². So the area increases according to the square of the distance. Hope that helps.
Thanks i understood
It's funny how I heard the name, and I heard about the concept and thought they were unrelated for some reason.