0
Speed of Light
Denoted with the symbol "c," the speed of light is 299,792,458 metres per second and is often rounded as 300,000 kilometres per second or 186,000 miles per second.
1,290 Questions
Was calculus used for the discovery of light speed?
Strange as it may seem, the speed of all electromagnetic waves was predicted long
before it was ever measured. After the speed was predicted, measurements of light-
speed supported the growing suspicion that light is electromagnetic radiation, because
the measured speed was so close to the predicted speed.
Measuring the speed of light is not easy, and several clever methods had to be invented
in order to do it. Calculus was almost certainly used at many points in the application
of these methods.
How many calories does it take to heat 10 grams of ice to 78 degrees C?
First, you need to melt the ice. Look up the heat of fusion of ice, and multiply that by the amount of grams.Then you need to heat the water, from zero degrees to 78 degrees. Look up the specific heat of water, and then multiply together all of the following: The specific heat; the mass; the temperature difference.
Finally, add the two together.
The speed of light in any material medium is less than it is in empty space.
When the object is at c then concave mirror produces which image?
The answer depends on ...
-- the location of 'c' in the drawing you're looking at
-- how the images are labeled on the list beside the drawing
How many kilometers per hour are in the speed of light?
Light is so fast that it is usually expressed as about 300,000 kilometers per second. If you multiply that by 3600 seconds / hour, you get the speed in kilometers per hour.
Can short-wave radio waves be diffracted around hills?
Yes. That happens regularly.
It also happens regularly with plain old AM radio. That's why you can keep listening to
AM radio as you drive through the hills near the city where the AM station is located.
What does the Reduce speed warning light mean on a 2000 Isuzu rodeo?
One can't help wondering what part of "Reduce Speed" you don't understand.
What travels at the speed of 300000 kilometres per second?
That is approximately the speed of light (c). In metric units it is exactly 299792458 meters per second (299792.458 kilometers per second). Even electrons in atoms travel at approximately the same speed (but always less than speed of light)
The relativistic contraction only involves the dimension parallel to the direction
of motion. Your meter stick would appear strangely skinny, but still 1 meter long.
Do sodium lamps emit ultraviolet light?
The field emitted by the reaction in the tube which is near 1000 degrees f emits
ultra high radiation. The radiation although in a small amount if exposed over a long
period of time has been thought to cause cancer, impotency and other maladies.
=========================================
Answer #2:
I've just now examined the emission spectrum of sodium in an electrical discharge,
and according to the layout I saw, ALL of the emission lines of sodium fall in the
visible band, between roughly 460 and 590 nanometers, with the doublet at about
590 nm being by far the strongest.
I've never heard of any serious objections to sodium municipal lighting on public health
grounds, and I don't know where the first answer came from.
Allegations like "has been thought" or "is reported" or "is suspected" or "studies show"
don't generally mean much if their source isn't identified, and the phrase "ultra high
radiation" is meaningless on its face.
How do you run at the speed of light in real life?
You cannot. You cannot even run at a millionth of that speed so don't waste your time.
Most likely cause is a faulty "driver" in the Body Control Module Very common problem for these cars Must be changed and programmed by the dealer About 400 Canadian if out of warranty
Use the definition of "index of refraction". In this case, you simply need to divide the speed of light in a vacuum by the index of refraction.
Does light travel at low speeds?
Normally, the answer to that kind of question would depend on what you call "low".
In the case of light, however, probably nobody would call it a 'low' speed, because
it's physically impossible for anything in creation to travel faster than light in a vacuum. It is possible for things to travel faster than light does in other media, but it's not exactly common, and it's still very much on the "fast" end of the scale.
How is lightyears the speed of light put into distance?
A light-year is the distance travelled by light in a year. It is simply used as a convenience, since the official SI unit - meters - results in very large numbers (for example, approximately 4 x 1016 meters to the nearest star).
Distances between planets in our Solar System are NOT usually measured in light-years, since a light-year is much more than those distances. Instead, the distances are expressed either in millions or billions of kilometers, or in astronomical units. One astronomical unit (AU) is the average distance from Earth to Sun (150 million kilometers).
Why is the speed of light limited in a vacuum?
The speed of light is not limited in a vacuum - the speed of light is fastest in a vacuum. But that is what Einstein called the "Cosmic Speed Limit" - nothing can move faster than the speed of light in a vacuum, or even quite asfast.
Does the speed of light rays increase when they pass through glass?
No, it is only refracted at each clear air to glass surface, even if the refractive index of the glass changes.
If an air to glass lens is vacuum coated with a fluoride film, it impoves the tranmision of light through the lens, e.g. the front lens of a telescope. The film can improve the tranmission of light by one half of a wave length. This trechnolgy was used by the British Navy during WW2 against the German warship the Graff Spay and others. The British vessels were able to see the enemy before they could be seen and were able to fire the first shots.
Why does light go in the speed of 300000000 meter per second?
Because a photon is massless. Since photons are massless, by the laws of physics all massless objects MUST travel at the speed of light.
E=MC^2 "E" is Energy, "M" is Mass, and "C" is the speed of light squared or multiplied by its self.
===========================================
Another contributor tried to respond to the same question:
Strange as it may seem, the speed of light was accurately predicted long before there was
any way to measure it. The prediction falls out naturally from the Physics and Math of
wave motion.
In the equation for a wave, a constant appears in one of the terms, and the speed of
the wave is the square root of the reciprocal of that constant.
When you take Maxwell's four equations of electricity and magnetism, and massage them
in such a way as to derive the equation of the electromagnetic wave that they would
produce, the constant in that particular place in the equation is the product of the
vacuum permittivity of space ... 8.854188 x 10-12 ... and the magnetic permeability
of space ... 1.256637 x 10-6 . Now watch closely as I handle these numbers, with
nothing up my sleeve:
The product is (8.854188 x 10-12) x (1.256637 x 10-6) = 1.11265 x 10-17 .
The reciprocal of that number is 8.987552 x 1016 ,
and the square root of that number, which should be the speed of the wave, is
299,792,462 meters per second ...
only 4 m/s different from the official, internationally accepted number !
Admittedly, this still doesn't answer your question of "why", but your question is now
"Why are the vacuum permittivity and the magnetic permeability of free space both
exactly the numbers that they are ?"
We hope you consider this to be some progress; but if you've simply lost all interest
by now, we'll understand.
A third response:
The speed of light is 300 000 000 m/s because we, as humans, defined what is 1 meter and what is 1 second. The speed of light itself is just a fundamental constant, a fact of this universe. It just "is."
In some branches of physics, the speed of light is just defined as 1 distance/time.
If you understand special relativity, consider what would happen if the speed of light were say, 10 m/s.
What have we found that travels closest to the speed of light?
Particles such as neutrinos and photons have been observed traveling very close to the speed of light. Neutrinos are known to have tiny but non-zero mass, while photons are massless particles that always travel at the speed of light in a vacuum.
