how to calculate speed of light at different temperature?

Answer 1

You don't need to calculate it.

c is c is c is c is c.

Unless you are looking for the apparent speed of light in an opically dense medium.

Then it's an experimental question. You could find it with interferometers or by a refraction experiment or just by simple stopwatch technique (if you have a pretty fast watch).

Answer 2

Temperature of what? If you mean the temperature of the medium, divide c by the index of refraction of the medium at that temperature. Some specifics for water, as a fraction of c:

.717 zero degrees C 226nm wavelength light
.727 100 degrees C 226nm wavelength light

.754 zero degrees C 1014nm wavelength light
.763 100 degrees C 1014nm wavelength light

Answer 3

The speed of light in vacuum is not temperature dependent, it is a universal constant. Any temperature dependence on the speed of light through a particular material will depend on the material.

Answer 4

Temperature does not affect the speed of light .

Answer 5

Lets begin with a little background!

In a medium of sodium atoms, light of a particular color still travels at a speed of several hundred thousand kilometers per second. This speed is known as the phase velocity. However, light of slightly different colors travel at different speeds. When a collection of different colored light passes through the medium, the speed of the unit, which is known as the group velocity, moves at a much slower speed. This is because the different components combine in an unusual way to cancel fast propagation, an effect common to all wave phenomena known as interference.

A track star, who runs the 100-yard dash in less than 10 seconds, would be hard pressed to perform the same feat in a vat of molasses. The same is true for light, but, instead of molasses, a cold medium is employed. Now imagine that you could switch a laser on or off to turn air into molasses or molasses into air. Then the track star's speed could be easily controlled. This is what the members of a Rowland Institute team have accomplished. In short, these scientists have put the "deep freeze" on light.

How cold was the medium? Very cold -- just a few microkelvins1 above absolute zero temperature. Absolute zero is the lowest possible conceivable temperature, a temperature at which microscopic constituents such as atoms and molecules stop their motions. It is the ultimate cold. In effect, every iota of heat is squeezed out of the system. Absolute zero is approximately -273o in Celsius, it is about -460o in Fahrenheit, and it is 0o in Kelvins by definition.

Dr. Hau's team found that, at a microkelvin, the pulse of light traveled through the cold, laser-bathed sodium atoms at an astonishingly slow speed of about 50 meters per second. But did the Rowland Institute physicists stop here? You bet they didn't! They went on to cool the gas to a temperature of about 50 nanokelvins!2 At this incredibly low temperature, the sodium atoms entered a new exotic state of matter called a Bose-Einstein condensate. Constructed for the first time in the laboratory only a few years ago in 1995, Bose-Einstein condensates have opened up a new exciting field in cryogenics.3 In this coldest of cold environments, the light pulse sped through the condensate at only 17 meters per second!

Besides generating an enormously rapidly varying index of refraction, the laser light had another important consequence for the cloud of sodium atoms. Normally, the cloud is opaque, meaning that light cannot travel through it. Light is absorbed as it enters an opaque medium. However, when the laser light was tuned to a particular color, the gas became clear, allowing about 25% of the pulse light to pass. This effect is known as electromagnetically induced transparency because laser light is used to render the cloud transparent.

To achieve the electromagnetically induced transparency, it is important for the cloud to be very cold so as to allow the laser light to interact efficiently with the sodium atoms.

Dr. Harris, one of the members of Dr. Hau's team, had previously slowed down light approximately 100-fold using the same method of electromagnetically induced transparency. Another group of physicists had used what-is-called self-induced transparency to achieve about a 1000-fold reduction. Thus, the Rowland Institute team smashed the previous world record for slowing down light by an amazing four orders of magnitude. The team hopes to eventually "bring light to its knees" by slowing it down to the "snail's pace" of a centimeter per second.5 Well, it's a fast snail.

Dr,. H