I mean what if it's not?, does it change anything?
2007-10-06 06:10:46 · 7 answers · asked by Grg 2 in Science & Mathematics ➔ Physics
Light speed is constant for a given medium it is traveling in. The fastest it goes is in a vacuum and that's about c = 3 X 10^5 km/sec or 186,000 miles per sec.
If light speed were not constant, that would change a whole lot of things. For example, L = ct where L is the wavelength of light at a given frequency f = 1/t and t is the time it takes to travel L.
Therefore, we'd have c = L/t = Lf . Thus, when c = constant (no matter what medium), we see that if the frequency of light increases, the wavelength has to shorten to keep c at the constant value. If c were <> constant, there would be no fixed relationship between L and f.
There's another light equation, E = hf; where E is the energy packed in a photon, h is a constant, and f is that same frequency as before. From the earlier equation we have f = c/L; so that E = h(c/L) = hc/L and if c were not constant the energy of each photon would not depend solely on its wavelength.
Bottom line, if c were not constant, most, if not all, the laws of electro-magnetic energy would be vastly altered and not the same as they are in our universe. These laws include the laws of optics; thus, at a very minimum, things would look different from what they are now.
2007-10-06 06:37:33 · answer #1 · answered by oldprof 7 · 0⤊ 0⤋
Yes, the speed of light is constant and is denoted as a c. The approximate value for speed of light is 3x10^8 m/s.
While the speed of light in a certain medium is constant, it is different for different media (like water, glass, oil, air etc.)
2007-10-06 06:31:05 · answer #2 · answered by lisse_aranel 2 · 1⤊ 1⤋
Yes, the speed of light is constant in any inertial reference frame. If it weren't, then all of Special Relativity would fall apart since it's based on that fact.
FWIW the measurement has been made millions of times and it's always been 299792458 m/s. Also, all of the phenomena predicted by SR have been measured and verified to be accurate.
Doug
2007-10-06 06:37:37 · answer #3 · answered by doug_donaghue 7 · 0⤊ 1⤋
Speed of light is constant as long as it is travelling in the same isotropic homogeneous medium. Speed of light can change if it enters another medium with different optical density.
For example, in vacuum or atmospheric air, it is 300,000 km/s. In water, it is 225,000 km/s and in glass it is 200,000 km/s.
2007-10-06 06:55:18 · answer #4 · answered by Madhukar 7 · 0⤊ 0⤋
depends on how fast u turn the light on
2007-10-06 06:15:29 · answer #5 · answered by cannonfodder39 2 · 0⤊ 2⤋
speed of light is contant always and every where
2007-10-06 06:19:24 · answer #6 · answered by Anonymous · 0⤊ 2⤋
Yes it is, 186,000 miles per second.
2007-10-06 06:19:08 · answer #7 · answered by MAD MEL 4 · 0⤊ 1⤋