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Anonymous users2024-02-10In 1850, the French physicist Foucault improved Fisso's method by using only a lens, a rotating plane mirror, and a concave mirror. The parallel light converges on the center of the concave mirror through a rotating plane mirror, and the time can be calculated by using the rotational speed of the plane mirror. Foucault measured the speed of light in this method at 298,000 km/s.
In addition, Foucault also measured the speed of light propagation in water, and by comparing it with the speed of light in the air, he measured the refractive index of light from air into water. After the particle theory has been overturned by the wave theory, this experiment once again made a judgment on the particle theory, and brought the final impact to the particle theory of light. In 1928, Carolas and Mitastad first proposed the use of the Kerr box method to determine the speed of light.
In 1951, the speed of light measured by BetszczChuan was 299793 kilometers per second. Light waves are a small part of the electromagnetic spectrum, and every electromagnetic wave in the electromagnetic spectrum has been precisely measured today. In 1950, Eisen proposed the cavity resonance method to measure the speed of light.
The principle of this method is that when a microwave passes through a cavity, it resonates when its frequency is a certain value. The wavelength of the resonant cavity can be calculated according to the length of the cavity, and the speed of light can be calculated from the wavelength and frequency of the wavelength and frequency of the cavity by converting the wavelength of the cavity to the wavelength of light in a vacuum. The most accurate speed of light ever calculated is based on wavelength and frequency.
In 1958, Froome found the exact value of the speed of light: kilometers and seconds. In 1972, Evenson measured the current optimal value of the speed of light in a vacuum:
Meter seconds. The determination of the speed of light is of great significance in the research process of optics. Although it took more than 300 years from the time people tried to measure the speed of light to the time when people measured the more accurate speed of light, every bit of progress during this period promoted the development of geometrical optics and physical optics, especially in the debate between the particle theory and the wave theory, and the determination of the speed of light provided a very important basis for this famous scientific debate.
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Anonymous users2024-02-09There is a special laser measuring instrument, you can find it by turning over the textbook of Jiangsu junior high school physics, which is the first book of Jiangsu physics, about the unit of light.
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Anonymous users2024-02-08The speed of light refers to the speed at which light waves or electromagnetic waves travel in a vacuum or medium. The speed of light in a vacuum is the maximum speed of motion of an object in nature that has been discovered so far.
It is independent of the speed of the observer relative to the light source, i.e. the speed of light measured in the inertial frame relative to the stationary and moving light source is the same. The mass of the object will increase with the increase of velocity, and when the velocity of the object is close to the velocity of light and silver, its mass will tend to infinity, so it is impossible for an object with mass to reach the speed of light. Only photons with zero rest mass are always moving at the speed of light.
The speed of light is superimposed on any speed, and the result is still the speed of light. The synthesis of velocity does not follow the laws of classical mechanics, but follows the laws of velocity synthesis of relative hand commas. <>
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Anonymous users2024-02-07How is the speed of light measured?
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Anonymous users2024-02-06Light is a wave and the speed of the wave is equal to its wavelength multiplied by the frequency. The speed of the wave (the speed of light) can be calculated by obtaining the wavelength and frequency.
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Anonymous users2024-02-051 Romer's satellite eclipse.
The measurement of the speed of light was first successful in astronomy because the vast expanse of the universe provided a large enough distance to measure the speed of light As early as 1676, the Danish astronomer Romer (1644-1710) first measured the speed of light Since any periodic process can be used as a clock, he succeeded in finding a very distant and fairly accurate "clock" from the observer, and Romer used a solar eclipse of Jupiter every certain period He observed that the time between two consecutive lunar eclipses was longer when the Earth moved away from Jupiter than when the Earth moved towards Jupiter, and he explained this phenomenon by saying that the propagation speed of light is limited Light is emitted from Jupiter (actually Jupiter's moons), and when the Earth moves away from Jupiter, light must catch up with the Earth, so the time between the two solar eclipses of Jupiter observed from the ground is longer than the actual time apart; This time is shorter when the Earth moves towards Jupiter Because the period of the moon around Jupiter is not large (about days), the above time difference should not exceed 15 seconds at the most appropriate time (when the Earth orbits to points A and A' in the orbit above) (the Earth's orbital speed is about 30 kilometers and seconds) Therefore, in order to obtain reliable results, the observations at that time were made continuously throughout the year Romer calculated the speed of light from the time change of the eclipse of the satellite and the diameter of the Earth's orbit Since only the approximate value of the radius of the Earth's orbit was known at that time, the speed of light was only 214300km s, although the speed of light value was far from the accurate value of the speed of light, it was the first record in the history of determining the speed of light Later, people used photographic methods to measure the time of the eclipse of Jupiter's moons, and after the accuracy of the measurement of the radius of the Earth's orbit improved, the speed of light obtained by the Romer method was 299840 60km s
2 Bradley's method of light travel.
In 1728, the British astronomer Bradley (1693-1762) used the method of light travel of stars, and once again concluded that the speed of light is a finite physical quantity When Bradley observed stars on Earth, he found that the apparent positions of stars are constantly changing, and within a year, all stars seem to orbit around the zenith in an ellipse with equal semi-major axis He believed that this phenomenon occurred because it took a certain amount of time for the light emitted by the stars to reach the ground, and during this time, The Earth's position has changed as a result of its revolution, and he measured the speed of light as:
c = 299930 km sec.
This value is close to the actual value
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Anonymous users2024-02-04How is the speed of light measured?
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