Speed of Light

The speed of electromagnetic radiation can be found using the refractive index of a material. The refractive index n is equal to the ratio of the speed of light in a vacuum to the speed of light in the substance. Electromagnetic waves propagate at different speeds in different materials.

X-rays travel at the same speed as visible light. All frequencies of electro-magnetic radiation (of which light is a very narrow band) travel at the speed of light (C) in a vacuum: 299,792,458 meters per second.

The speed of light varies in different medium. Given an angle of incidence other than 90 or 0, the wave will shift direction an amount determined by its frequency. The higher the frequency, the greater the shift. The transition between two medium of different refractive indices causes a variation in the phase velocity of the wave, but does not affect its frequency.

its known that the speed of light is =3 x 108 m/s

and speed=distance/time distance=speed x time

=3 x 108 m/s x 60

=18 x 109 metres

its also known that 1000m=1kilometre

18 x 109 metres=18 x 106 kilometres

hence distance travelled by light in 60 seconds is 18 x 106 kilometres in vaccuum

No. The person who succeeds in doing this will certainly win the Nobel Prize in Physics.

According to our understanding of the physical world, there is no way to exceed the speed of light. The math seems to disallow it. However, our understanding of physics and reality is woefully incomplete, and it is at least remotely possible that someone will make a breakthrough so stunning and complete that it will shatter our current physical theories and rewrite them overnight.

I do not expect this to happen within my lifetime.

When you have an interest in more signficant figures: 299,792,456 m/s. It was measured in 1983 using wavelengths of a certain light from an atom, and that is what we got stuck with.

When the light is less energetic than X-rays and is moving through something other than a hard vacuum.

When you are accelerating significantly, you can get all sorts of funny values.

When you measure the speed of light over a path involving significant mass, you get a "path speed" of less than c even if it is through a vacuum. (Shapiro time delay.)

Light travels through different types of matter at different speeds

Ultraviolet (UV) light has a higher frequency (and a shorter wavelength and shorter period) than violet light. It is more energetic, too. We can't see UV light as our eyes only see up through violet. The shorter wavelengths of the UV light are something we cannot detect with our eyes. We can see (in order of increasing frequency) red, orange, yellow, green, blue and violet light. The UV light is outside the range of our vision.

One way, is to turn on your light switch and observe how long it takes for the light to reach to the other side of the room. (How long it takes for the room to go from dark to light.) Be careful not to blink or you'll miss it.

True

The sun is roughly 8 minutes and 19 seconds away from earth in light speed!!!

Imagine how far away it is in normal earth speed!?!?

The speed of light is about 186,000 miles per second.

The speed of light is 299,792,458 meters per second - in a vacuum or 186,282 miles per second in a vacuum. And according to the theories of motion - nothing can travel faster than the speed of light. If it does - it bends time and time will slow down and eventually - as the speed increases - time will start going backward - and you will travel back in time!!! And of course this is theory - it has never been tested - as the fastest movement - relative the the person measuring the movement) has never even approached 50% (93,000 miles per hour) of the speed of light!

The speed of light - as all speeds are measured - is determined by the distance traveled - divided by the amount of time it took to travel that distance. A race car, for example, measures it's speed by the amount of time to travel a specific known distance (quarter mile - or 500 miles) divided by the time it took to travel that distance.

The speed of light is something we've figured out only in the last 100 years, right? Well, once more, our forebears surprise us. It turns out we've known the speed of light since before the birth of Johann Sebastian Bach.

That knowledge came close on the heels of the invention of the first telescopes in the early 1600s. In 1644, Ole Roemer was born in Jutland, Denmark. He took up the new study of astronomy with the early greats of that field.

By 1675 Roemer was 31 and working in Paris with Picard. He was interested in the movement of Jupiter's nearest moon. He tracked it as it orbited in and out of Jupiter's shadow. It entered the shadow, then reemerged exactly 42 hours, 28 minutes, and 35 seconds later. It moved with constant and exact regularity.

So Roemer measured 100 cycles and found that in one hundred cycles, Jupiter's moon could be relied upon to emerge EVERY TIME - right on schedule - to the exact second!! So he measured different lengths of time!! One was six months -- 100 laps -- and it was then that Roemer set his clocks and focused his telescope on Jupiter in the winter. In the spring - he waited and waited - but no moon appeared!! Finally it danced out of the shadows a full 15 minutes late. But why was the moon late - there must be a reason!

After much discussion, Roemer concluded that the moon was still appearing at the same time - and it was the earth that had moved!! The earth had swung hundreds of millions of miles away from Jupiter during the long winter months so light had to travel that vast distance to see Jupiter's moon!!! It had obviously taken the extra time to do so. (Also discovering that earths orbit around the sun is egg-shaped - NOT a circle)!

He put pencil to paper and concluded that light had to move 192,500 miles per second to lose just those fifteen minutes. Not bad at all! Roemer was within three percent of the right value (186,282 miles per second). And that was less than 70 years after we first had telescopes.

Just to be sure, Roemer calculated when we'd get that 15 minutes back, as the earth moved back toward Jupiter and spring began. He was right again.

Today the speed of light is measured - and found to be accurate - by pointing a laser to one of the many groups of mirrors and reflectors that were set up on the moon by the 1970's moon landing missions. Now computers accurately measure the speed light with a laser - and can determine the exact speed of light to within 1/quadtrillionth of a second! These mirrors also measure the movement of earthquakes on the earth - from the moon - to within 1/10,000,000,000th of an inch!

not really since visible light is only a small part of the electromagnetic spectrum. For u 2 see an object it must give off or reflect wavelengths of visible light.

any questions about this feel free to ask:]

It speeds up.

Air and water are both media (plural form of medium). Each one of them has a different speed of light. As the incident ray passes from air to water, it refracts to be closer to the normal. A refraction occurs when there is a change in the speed of light. A change in the speed of light occurs when there is a change in media. In this case the media is changed from air to water. The second medium (water) must also have a lower speed of light in order for refraction to occur

Light travels at a speed of 186,000 miles per second, in a vacuum.

Silicon, with an index of 3.96, is the lowest I could find.

The speed of sound in air is about 300 meters per second. (320 is closer still). .
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The speed of light in a vacuum is 300 000 000 meters per second.

So the speed of light in a vacuum (in air it is only slightly different) is about one million times the speed of sound in air.

All wavelengths are the same physical phenomenon ... electromagnetic radiation ...

whose speed depends on the electrical properties of the medium in which it is

propagating. Why would you think that they should travel at different speeds ?

The speed of light was measured by Ole Christensen Romer. He watched the moons of Jupiter, and observed that their movement around Jupiter appeared slower when the earth was moving away from Jupiter than when earth was moving towards Jupiter. This was because the light from the moons took longer to reach earth. He concluded that the speed of light is 220,000 kilometers per second. It is in fact 300,000 km/s, so he wasn't too far off.

In 1849, Hippolyte Fizeau performed the first earth-bound measurement of the speed of light. A beam of light was reflected off a two-way mirror; it then went through the teeth of an opaque cogwheel rotating very fast, was reflected off a mirror, returned through the teeth of the cogwheel, and went through the two-way mirror to a detector. In the time it took for the light to get from the wheel to the mirror and back, the wheel rotated slightly, which meant that some of the light which had previously gone through was blocked by the cogs. So the finiteness of the speed of light made the light slightly dimmer. By measuring its brightness, he calculated that the speed of light in vacuum was 313,000 km/s.

Fizeau's experiment was important because it could be used to measure the speed of light in any medium, whereas Romer's observation only worked for the speed of light in vacuum. Fizeau discovered that the speed of light is faster in air than in other media. This helped to resolve the long-standing question of whether light consists of particles or waves - the particle theory supported by Isaac Newton predicted that the speed of light would be slowest in a vacuum.

Someone observed that the speed of light was (up to experimental error) exactly equal to 1 / sqrt(epsilon * mu), where epsilon and mu are fundamental constants connected with electricity and magnetism, respectively. At the time, this observation just seemed weird. But when James Clerk Maxwell published his equations for electromagnetism, which predicted the possibility of waves travelling at this speed, it all made sense: light consists of electromagnetic waves. So if we want to measure its speed we only have to measure epsilon and mu. The values of epsilon and mu are different in different media, so this explains the differences in the speed of light.

The speed of light in a vacuum is approximately 300,000 kilometers per second or about 186,000 miles per second. It is a constant value in the universe and serves as the maximum speed at which all electromagnetic radiation, including visible light, can travel.

Radio waves and light are the same exact physical phenomenon, and

differ only in their wavelength (frequency). Their speeds are identical.

Light with a lower frequency will have a longer wavelength. Frequency and wavelength are inversely proportional to each other (i.e. as one increases, the other decreases and vice-a-versa). The product of frequency and wavelength is the speed of light.

No. Bullets travel from a few hundred feet per second up to several thousand feet per second, and lightening is much faster than that. According to various sources, lightening travels at either the speed of light, or about half of that, or about a third of that.