Can We Measure the Speed of Light in Different Materials?

In summary, the speed of light is measured in objects by using interferometry or timing the light pulse travels. For solids, the Brewster angle can be used.
  • #1
ravisastry
52
0
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 !
 
Science news on Phys.org
  • #2
ravisastry said:
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 !
Welcome to Physics Forums.

Just out of interest, why do you want to know? Why are you interested in the speed of light in transparent materials?
 
  • #3
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
In terms of materials a viable way would be interferometry
 
  • #5
thanks...now, ill google "interferometry"
 
  • #6
ravisastry said:
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 !
I look forward to it.
 
  • #7
ravisastry said:
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 !

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
Feldoh said:
In terms of materials a viable way would be interferometry
That's good for gases and fluids. Not so much for solid materials.

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
guys, I am not getting what i was looking for "http://en.wikipedia.org/wiki/Interferometry" [Broken] 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 :)
 
Last edited by a moderator:
  • #10
K^2 said:
That's good for gases and fluids. Not so much for solid materials.

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
K^2 said:
That's good for gases and fluids. Not so much for solid materials

For solids you can use the Brewster angle. Kind of fun to measure the speed of light in coal.
 
  • #12
Vanadium 50 said:
Kind of fun to measure the speed of light in coal.

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! :biggrin:
 

What is the speed of light?

The speed of light is a fundamental physical constant, denoted by the letter c, which represents the speed at which light travels in a vacuum. It is approximately 299,792,458 meters per second (m/s) or 670,616,629 miles per hour (mph).

How is the speed of light measured?

The speed of light can be measured using various methods, such as the Foucault apparatus, the Fizeau experiment, and the Michelson-Morley experiment. These experiments involve measuring the time it takes for light to travel a known distance and using the formula c = d/t to calculate the speed.

Why is the speed of light considered a constant?

The speed of light is considered a constant because it does not change regardless of the observer's frame of reference. This was first demonstrated by Albert Einstein's theory of relativity, which states that the speed of light is the same for all observers regardless of their motion or the motion of the source of light.

Can the speed of light be exceeded?

According to our current understanding of physics, the speed of light cannot be exceeded. This is because as an object approaches the speed of light, its mass increases infinitely, making it impossible to accelerate further. However, some theories, such as string theory, propose the existence of particles that can travel faster than light.

How has the measurement of the speed of light evolved over time?

The first attempts to measure the speed of light were made in the 17th century by scientists such as Galileo and Ole Rømer. However, it was not until the 19th century that more accurate measurements were made using experimental methods. Today, the speed of light is a precisely measured constant, and its value has been refined over the years through new technology and experiments.

Similar threads

Replies
19
Views
1K
Replies
15
Views
3K
Replies
8
Views
10K
Replies
15
Views
1K
Replies
4
Views
2K
  • Optics
Replies
4
Views
1K
  • Optics
Replies
25
Views
2K
Replies
40
Views
14K
Back
Top