2007-04-06 13:21:06 · 5 answers · asked by rolando e 1 in Science & Mathematics ➔ Physics
The speed of light is a constant. The speed of sound is much much slower and depends on the density of the medium it is traveling through.
2007-04-06 13:25:16 · answer #1 · answered by Roman Soldier 5 · 0⤊ 0⤋
The speed of light depends on the medium the light is traveling in. In a vacuum, c ~ 186,000 miles per sec or 300,000 km per sec. In other media (like water or glass), light travels at a predictable, but slower velocity. The reason a pencil appears to break at the surface of a glass of water is because the light in the water travels slower than the light above the water.
For both sound and light, the time it takes to travel one wavelength (t) is found by L = vt; where L = the length of one cycle, v = the velocity of the wave, and t = the period = 1/f; where f = the frequency of the wave. If we are talking about v = c = speed of light, we have L = ct = c/f; so that fL = c. Because c = constant for light in a given medium, when raising the frequency of the light, its wavelength has to shorten to maintain the constant c value.
Same thing for sound if its velocity remains fixed. That is, higher frequency means shorter wavelengths and vice versa to keep the speed fixed. This comes from L = vt = v/f; so that Lf = v.
We've already said that c varies according to the medium light is traveling. Same can be said of sound. In dense media, like wood, sound travels faster than in air, for example. This means the wavelengths must be longer in wood than in air for the same frequency (the same pitch) to give the higher velocity.
Velocity also depends on a number of other things in air. For example sound increases in velocity for warmer temperatures. It also increases for denser air. This is why the speed of sound is typically lower at commercial jet altitudes than on the surface of the Earth. However, in general, the speed of sound varies between 500 and 1100 mph in the air.
Power is, by definition, energy expended over some specified time interval. Energy for a photon of light is E = hf; where h is a constant called Plank's constant. f = 1/t = the frequency of the light. Thus power = E/t = h/t^2; where t = the period of the light wave. This gives us the power of one photon of light measured for one period.
Power for sound transmission depends on the intensity (loudness) of the sound. Intensity is frequently measured in decibels, where 120 decibels can start to do some serious harm to hearing. The equations are not as straightforward as those of light. [See source.]
2007-04-06 21:52:54 · answer #2 · answered by oldprof 7 · 0⤊ 0⤋
Speed of light = 299 792 458 m / s
Speed of sound at sea level = 340.29 m / s
POWER has many meanings, most of which imply (a capacity for) control or force, (though in physics the terms "power" and "force" have different meanings).
In Physics, POWER is the amount of work done or energy transferred per unit of time.
2007-04-06 21:06:26 · answer #3 · answered by pedros2008 3 · 0⤊ 0⤋
the speed of light is a constant like what the other person said.. and the speed of sound depends on the medium the sound is travelling to... usually it's higher in solids and lower in gases... not sure about the last one, but i think the formula P = Fv applies...
2007-04-06 21:14:07 · answer #4 · answered by Elyre 1 · 0⤊ 0⤋
Light is Electromagnetic Radiation - 186,000mps
Sound is acoustic vibration - 700mph
2 completely different phenomena
2007-04-06 20:28:45 · answer #5 · answered by Anonymous · 0⤊ 0⤋