I have read about Armand Fizeau used a rotating wheel, And Albert Michealson's device, but nothing that i have read has given real exact instructions how to construct a device that could do it. I am not looking for accuaracy as much as i am consistancy. Dont bother giving me a post saying its not possible, because it is. I just want some brilliant mind to explain how the different machines worked, and how i could build one.
2006-08-22 15:57:12 · 8 answers · asked by Adam 4 in Science & Mathematics ➔ Astronomy & Space
It is very common for attemps to try to measure the speed of light directly by actually timing how long it takes for a ray of light to go a given distance (some of these methods can get rather sophisticated).
But I offer to you another method...using the index of refraction of a known substance.
When light enters a medium which is not a vacuum, it slows down. The more optically dense the medium, the slow light travels. The ratio of the speed of light in a vacuum (c) to the speed of light in a given medium (v) is called the index of refraction (n).
n = c / v
The index of refraction for many common sunstances is known, for example, the index of refraction of water is about 1.33, this would be a good estimate for most [pure] water.
When light enters a substance at an angle and slows down, it bends. The amount the light ray bends depends upon the index of refraction of the two media.
Using Snell's law, one can calculate the angle light will travel at as it enters/exits a mediu,
n1*sin(theta1) = n2*sin(theta2)
where n1 and n2 are the indicies of refraction of the first and second medium which light is travelingin and theta1 and theta2 are the incidence and refracted angles (measured to the normal) of the path followed by light.
If you can set up a system in which a laser beam (from a laser pointer perhaps) can be shown through a tub of water in a way that will allow you to measure the angles, from this, one can calculate the speed of light in that medium. Since you know the speed of light in the medium and you know the index of refraction, you can then back calculate the speed of light in a vacuum.
Using this method, one does not have to have quick reflexes or a very larger distance over which to shine a light, it just comes down to geometry.
http://scienceworld.wolfram.com/physics/IndexofRefraction.html
2006-08-22 16:28:27 · answer #1 · answered by mrjeffy321 7 · 1⤊ 0⤋
The rotating mirror method should be doable, but I have never tried it. See the source.
Because light moves so fast, you need the stationary mirror as far away as possible; certainly thousands of feet and preferably many miles. It will require EXTREMELY precise pointing of the laser to hit that distant mirror and then be able to find the returning reflection. Also, as the rotating mirror turns, the outgoing light beam direction will change so as to miss the stationary mirror most of the time, so the returning reflection will be a pulsing light, on only during the short time the mirrors are lined up perfectly and off the rest of the time. This can be improved somewhat by having something like a disco ball, with many mirrors, so that you get a visible return reflection more than once per rotation. Any way you look at it, it is a tough experiment to do.
The toothed wheel method is simpler, but you need LOTS of SMALL teeth and a very FAST ROTATION. Since light travels 186,000 miles a second, if the distant mirror is 1 mile away you need the wheel to move from a space to the nearest tooth in 2/186,000 seconds, or about 10 millionths of a second. With a 100 tooth wheel, that is about 60,000 RPM!
2006-08-23 10:41:16 · answer #2 · answered by campbelp2002 7 · 0⤊ 0⤋
Fizeau's experiment with a toothed wheel and a distant mirror isn't too difficult to perform yourself. It's easier now than it was for him with a low-powered laser. You shine the laser at the mirror between the teeth of the rotating wheel, and increase the speed of the wheel until you can't see the reflected beam. You and the laser of course are on the opposite side of the wheel from the mirror. I calculate that with a practicable number of teeth and rate of rotation, the mirror needs to be at least 5 km. away. I've never done this experiment. I'll be interested to hear how you get on. Another approach would be to create a standing wave pattern of microwaves between your oscillator and a reflector. Measure the distance between nodes with a test antenna; that's half a wavelength. Then measure the frequency of the waves with a test antenna and frequency counter. c=f times wavelength. You could set up all this equipment on a kitchen table.
2006-08-23 00:12:25 · answer #3 · answered by zee_prime 6 · 0⤊ 0⤋
First you have to find and determine the speed of Gonzales. The speed of light is very close to his speed ;however a little slower.
There is slight margin of error.
Another way would be to measure the energy in terms of the water temperature changes. so you have a delta energy.
E-delta should equal the mass of heat injecfted in the water times the velocity square of the moving heat.
to calculate the speed of light you can use Henri PoinCarre formula of heat Energy.
The velocity square of light would equal E-delta /mass of the heat radiation.
Another method not as accurate ,would be to use rotating wheel with mirror and and rotate at high speed ,determine the number of rotation till you have an interference pattern. divid the distance in terms of rotation and divide by the time and you have velocity.
Of course to measure the average speed of light in the universe relative to the earth you have to measure the speed of light at the outskirt of the Universe and than the speed of light relative to the earth add them together divide by 2 and you would have an average.
However no one has been able to ascertain what the velocity of light is at the outskirt of the Universe.
If a method could be developed , and whosever develops it he would deserve the Nobel Prize of science.
You can try it .
Fizeau experiment is a little out dated, I would not spend too much time on it.
2006-08-24 11:38:18 · answer #4 · answered by goring 6 · 0⤊ 1⤋
You can measure the speed of light with a microwave oven and some chocolate chips:
http://superpositioned.com/articles/2006/03/09/measure-the-speed-of-light-with-chips
2006-08-22 23:27:04 · answer #5 · answered by Anonymous · 0⤊ 0⤋
i tried to measure it a long time ago...and the amount is really freaking me out..so i stopped...i didn't have any equation but i measure it according to logic..sadly, i have forgotten how i measure it...
trust me, you don't want to know about it! it'll probably make your day worst!
2006-08-22 23:25:42 · answer #6 · answered by Foreigner 2 · 0⤊ 0⤋
turn off the bathrom lite and go back to bed
2006-08-22 23:03:47 · answer #7 · answered by crusinthru 6 · 0⤊ 0⤋
You will need a yard stick and a stop watch.
2006-08-22 23:02:39 · answer #8 · answered by da_hammerhead 6 · 0⤊ 1⤋