- #1
ravisastry
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Hi, how is the speed of light measured in objects such as water, glass, diamond etc ? what are the tools and techniques used. thanks in advance !
Can We Measure the Speed of Light in Different Materials?
- Context: Undergrad
- Thread starter ravisastry
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Discussion Overview
The discussion revolves around how the speed of light is measured in various materials such as water, glass, and diamond. Participants explore different methods and tools used for these measurements, particularly focusing on techniques applicable outside of a vacuum.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- Some participants inquire about the measurement of light speed in materials other than vacuum, expressing interest in potential theoretical implications.
- Interferometry is proposed as a viable method for measuring light speed in certain materials.
- Indirect methods such as using Snell's law and measuring refraction angles are suggested for transparent materials.
- A participant describes an experimental setup involving an oscilloscope, LED, photo-diode, and mirrors to measure light speed with high precision.
- Another participant raises a question about the time it takes for light to traverse a specific thickness of glass and the number of atoms it encounters, seeking information on photon absorption and re-emission times.
- Discussion includes the suggestion that atomic physics or quantum mechanics may be necessary to address certain questions about light interaction with materials.
- Some participants note that methods suitable for gases and fluids may not apply to solid materials, and mention the Brewster angle as a potential measurement technique for solids.
Areas of Agreement / Disagreement
Participants express a range of methods and ideas, but no consensus is reached on a singular approach or solution to measuring light speed in different materials. Multiple competing views and techniques are presented.
Contextual Notes
Participants highlight limitations in existing methods and the complexity of measuring light speed in solids, indicating a need for further exploration into atomic interactions and experimental setups.
- #2
Hootenanny
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Welcome to Physics Forums.ravisastry said:
Just out of interest, why do you want to know? Why are you interested in the speed of light in transparent materials?
- #3
ravisastry
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just wanted to know how speed of light is calculated in places other than vaccumm...who knows, the answer i get, might help in formulating some new theory !
- #4
Feldoh
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In terms of materials a viable way would be interferometry
- #5
ravisastry
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thanks...now, ill google "interferometry"
- #6
Hootenanny
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I look forward to it.ravisastry said:
- #7
stevenb
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ravisastry said:
If you don't mind an indirect method, you can use Snell's law and measurent of refraction angles with oblique incidence. This should work well with the highly transparent materials you mentioned.
- #8
K^2
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That's good for gases and fluids. Not so much for solid materials.Feldoh said:
If you have a thick enough slab of material, and you send the beam through it a few times with mirrors, you can just time it directly.
One of the experiments done in the Intermediate Physics Lab in our department is measurement of speed of light using an oscilloscope, and LED, a photo-diode, and some mirrors. You basically use the oscilloscope to measure time it takes a pulse of light to travel a certain distance. You can get something like 10-3 precision with that.
- #9
ravisastry
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guys, I am not getting what i was looking for "http://en.wikipedia.org/wiki/Interferometry" the link doesn't tell about speed of light measurement.
k^2 ... what i was looking for is, say you have a glass slab of 1 cm thickness. how much time would like to traverse this and roughly, how many atoms would it encounter. we can take any substance, not just glass. i'd like to know the time gap between a photon absorption and re-emission in any atom. do we have an experiment or ready made answer for my question :)
k^2 ... what i was looking for is, say you have a glass slab of 1 cm thickness. how much time would like to traverse this and roughly, how many atoms would it encounter. we can take any substance, not just glass. i'd like to know the time gap between a photon absorption and re-emission in any atom. do we have an experiment or ready made answer for my question :)
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- #10
Danger
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K^2 said:
You might have to get into atomic physics or maybe even quantum mechanics in order to get your answer. I am over my head just by posting the foregoing, so I can be of no further help. Believe, though, that any reflection/refraction is a consequence of electron shell structure.
- #11
Vanadium 50
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K^2 said:
For solids you can use the Brewster angle. Kind of fun to measure the speed of light in coal.
- #12
Danger
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Vanadium 50 said:
That obviously brings to mind that there might be a new method of medical stool analysis to be patented here. Damn!, but I hate you!
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