Question

Speed of light in vacuum is _______ m/s.

Answer 1

Hint: Speed of light in a vacuum is a universal constant. Speed of light in a vacuum is a universal constant. Maxwell’s equations are used to calculate the value of light. Nothing can travel faster than the speed of light.

Complete step by step solution:
The history of determining the speed of light is very interesting. It is one of the fundamental values of physics which became accurate as the measurement tools and the theories became more prominent.
At first, it was believed that the transmission of light is instantaneous and does not take any time to travel from one place to another. Galileo first questioned the validity of the statement. However, the lack of good equipment restricted his research in this domain.

The first estimate of the speed of light was given by Olaus Roemer in 1676. The calculation was made using the Earth-Sun-Jupiter geometry. However, the lack of accurate measurement gave him a value of 214,000 km/s.

The next estimate was made by James Bradley in 1728, and he mentioned the speed of light as 301,000 km/s. He used the stellar aberration technique to come up with this number.

The first accurate estimate of the speed of light was possible after the advent of Maxwell’s theory of electromagnetism. The calculation was done by measuring the magnetic permeability and electric permittivity of open space. Rosa and Dorsey used the theory to obtain a value of 299,788 km/s, which is very close to the accurate value. Later, the usage of lasers, and microwave interferometer gave the accurate results. Now, the accepted value of the speed of light is, 299,792.458 km/s.
However, for the sake of simplicity we consider this value as,
$c=3\times {10}^8$

Note:
As the speed of light is a universal constant, we use this value to define the unit of length. One meter is defined as the distance travelled in vacuum by light in a time interval of 1/299,792,458 of a second. As this is a universal constant, you need to remember this value. This value is useful in a lot of questions and you have to consider the following value if nothing is mentioned in the question,