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  4. How many times would a light ray be reflected inside a circular mirror?
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How many times would a light ray be reflected inside a circular mirror?

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Offline hamdani yusuf (OP)

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How many times would a light ray be reflected inside a circular mirror?
« on: 21/08/2017 09:16:13 »
How many times would a light ray be reflected inside a circular mirror?

Let's say we have a circular mirror which is reflective in inner side. A laser beam is shone through a small hole on the mirror. How many times the laser beam would be reflected, if the incoming angle is 10 degrees?
« Last Edit: 21/08/2017 13:44:20 by hamdani yusuf »
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Offline chris

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Re: How many times would a light ray be reflected inside a circular mirror?
« Reply #1 on: 21/08/2017 10:43:40 »
This is effectively how a fibre optic works.
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Offline hamdani yusuf (OP)

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Re: How many times would a light ray be reflected inside a circular mirror?
« Reply #2 on: 21/08/2017 13:53:26 »
Quote from: chris on 21/08/2017 10:43:40
This is effectively how a fibre optic works.
I think the answer for the question needs math technique/tricks which are not readily available in most school textbooks.
There are more to explore, which I'll add to the playlist later as I have the time.

Sorry for the wrong link I put in the opening post. It has been corrected now.
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Offline chris

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Re: How many times would a light ray be reflected inside a circular mirror?
« Reply #3 on: 22/08/2017 20:01:47 »
I think the answer will depend upon the quality of the mirror; even tiny losses will quickly turn all of the energy in the photons into heat.
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Re: How many times would a light ray be reflected inside a circular mirror?
« Reply #4 on: 25/08/2017 18:30:46 »
Quote from: hamdani yusuf on 21/08/2017 09:16:13
How many times would a light ray be reflected inside a circular mirror?

Let's say we have a circular mirror which is reflective in inner side. A laser beam is shone through a small hole on the mirror. How many times the laser beam would be reflected, if the incoming angle is 10 degrees?
There is no angle using a circle, the light remains linear.
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Offline hamdani yusuf (OP)

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Re: How many times would a light ray be reflected inside a circular mirror?
« Reply #5 on: 18/03/2022 07:59:43 »
Quote from: chris on 22/08/2017 20:01:47
I think the answer will depend upon the quality of the mirror; even tiny losses will quickly turn all of the energy in the photons into heat.
Let's assume that the loss from the mirror is negligible, at least until the light exit again through incoming hole.

First step to answer the question about reflection of light in a circle. Introducing a new variable : order of reflection. Using incoming angle to calculate ratio between order of reflection and number of reflection.
« Last Edit: 18/03/2022 08:01:44 by hamdani yusuf »
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Re: How many times would a light ray be reflected inside a circular mirror?
« Reply #6 on: 18/03/2022 08:04:15 »
Next step to answer the question. Discovering a hidden variable implicitly stated in the question, which is greatest common factor between order of reflection and number of reflection.
After the value of s is obtained, we need to subtract by 1 to get the number of reflection, because when the head of the ray comes back to incoming point, it will leave the circle.
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Re: How many times would a light ray be reflected inside a circular mirror?
« Reply #7 on: 18/03/2022 08:54:39 »
If the beam has a finite width (and diffraction means it will have) them you need to consider the "focussing" effect of the curved mirror.
Essentially the light will be scattered in every direction.
Incidentally, unless the mirror has infinite mass, the wavelength will also be scrambled.

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Re: How many times would a light ray be reflected inside a circular mirror?
« Reply #8 on: 18/03/2022 10:17:05 »
I see this as an idealized math problem instead of realistic physics problem.
The effects from finite width of the light beam can be addressed/minimized by making the circle large enough.
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Re: How many times would a light ray be reflected inside a circular mirror?
« Reply #9 on: 18/03/2022 13:45:43 »
So, not actual science then...
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Re: How many times would a light ray be reflected inside a circular mirror?
« Reply #10 on: 20/03/2022 04:57:58 »
Quote from: Bored chemist on 18/03/2022 13:45:43
So, not actual science then...

It's a math problem. If you don't think that math is science, then you're right.
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Re: How many times would a light ray be reflected inside a circular mirror?
« Reply #11 on: 20/03/2022 09:44:24 »
Quote from: hamdani yusuf on 20/03/2022 04:57:58
Quote from: Bored chemist on 18/03/2022 13:45:43
So, not actual science then...

It's a math problem. If you don't think that math is science, then you're right.
It would be a math problem if the mirror was a polygon.
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Re: How many times would a light ray be reflected inside a circular mirror?
« Reply #12 on: 20/03/2022 10:09:21 »
Quote from: Bored chemist on 20/03/2022 09:44:24
It would be a math problem if the mirror was a polygon.
Why does it stop being math problem when the number of sides of the polygon is increased toward infinity, i. e. becomes a  circle?
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Offline Bored chemist

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Re: How many times would a light ray be reflected inside a circular mirror?
« Reply #13 on: 20/03/2022 10:14:32 »
Quote from: hamdani yusuf on 20/03/2022 10:09:21
Quote from: Bored chemist on 20/03/2022 09:44:24
It would be a math problem if the mirror was a polygon.
Why does it stop being math problem when the number of sides of the polygon is increased toward infinity, i. e. becomes a  circle?
Because it stops working.
If a beam of light hits a curved surface, it's no longer a beam.
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Re: How many times would a light ray be reflected inside a circular mirror?
« Reply #14 on: 20/03/2022 12:16:10 »
Quote from: Bored chemist on 20/03/2022 10:14:32
Because it stops working.
If a beam of light hits a curved surface, it's no longer a beam.
What prevents a mathematical ray from having infinitesimally narrow width? 
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Re: How many times would a light ray be reflected inside a circular mirror?
« Reply #15 on: 20/03/2022 13:11:00 »
Diffraction stops it being scientific.
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Re: How many times would a light ray be reflected inside a circular mirror?
« Reply #16 on: 20/03/2022 21:45:41 »
In geometry, a ray can be defined as a part of a line that has a fixed starting point but no end point.
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Re: How many times would a light ray be reflected inside a circular mirror?
« Reply #17 on: 20/03/2022 22:05:30 »
How many times would a light geometric ray be reflected inside a circular mirror?
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Re: How many times would a light ray be reflected inside a circular mirror?
« Reply #18 on: 20/03/2022 22:24:44 »
Quote from: Bored chemist on 20/03/2022 13:11:00
Diffraction stops it being scientific.
How does a curved surface create diffraction?
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Re: How many times would a light ray be reflected inside a circular mirror?
« Reply #19 on: 20/03/2022 22:34:13 »
Quote from: hamdani yusuf on 20/03/2022 22:24:44
Quote from: Bored chemist on 20/03/2022 13:11:00
Diffraction stops it being scientific.
How does a curved surface create diffraction?
I wasn't aware that anyone had said that it did.
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