Value of C- Definition, Value and Measuring

Introduction

c is nothing but an abbreviated form of the speed of light. The speed of light is defined as the speed of a light photon in a vacuum. The SI unit of the speed of light is m/s and is abbreviated as c. The value of c is considered constant in every part of the universe. There are various applications of the value of the speed of light in physics. Read on to learn more.

The Value of Speed of Light

The value of the speed of light, also known as c equals 299792458 m/s ≅ 3×10⁸ m/s. In space, the speed of light is measured in microseconds, but here the SI unit of the speed of light is m/s. The speed of light applies to visible light and all types of electromagnetic radiation. Numerous experiments and studies have been conducted to find the value of the speed of light. From ancient Greeks, who considered the travelling of light to be of infinite speed to the experiments of renowned scientists deriving the present value of c.

Scientists used several astronomical, mechanical, and electromagnetic methods to reach the point of accuracy for the value of c. After these experiments, the value of c was fixed at 299792458 m/s. During that time, a metre was considered as “the length of path completed by a light photon in vacuum during 1/299792458 time period of a second”. The value of the speed of light plays a major role in Physics.

Role of the Value of c in Physics

In the dynamics of moving objects, the value of the speed of light plays a vital role in providing a link between matter and energy. This relation is given by the formula E = mc² and is also called the equivalence of mass and energy.

The speed of light is considered the observer’s initial frame of reference since the value of c is constant for all parts of the universe. Einstein created this postulate in 1905 as invariance of the speed of light. As a consequence of this postulate, several theories were explored and created. One of them is the speed of light, known as c, at which all the particles and waves travel in a vacuum.

Albert Einstein gave a special theory of relativity which gave a few consequences regarding the invariance of c. Many other experiments and predictions are made with the help of the value of c. It helps with the fundamentals of physics. The value of c does not vary with changing time or location and is considered constant throughout spacetime.

Light Propagation

Light has been described as an electromagnetic wave in classical physics, and its behaviour has been described in Maxwell’s equations. In modern physics, light is described as the photons of the electromagnetic field by the basic excitations. Photons are defined as massless units in quantum electrodynamics and travel in the vacuum at the speed of light.

When the photons travel in a medium, the speed of light varies as per the different types of light waves. The speed at which light travels in different phases of a medium is called phase velocity. Phase velocity is vital in determining the travelling of a light wave from one medium to another. This determination is termed the refractive index of a material and varies by the density of the medium.

Ways of Measuring the Value of c

There are various methods to measure the value of c. Several astronomical, electromagnetic, and mechanical methods are used to measure the exact value of c. Scientists have done various experiments to fix this speed of light in a vacuum. After all the observations and experiments, the scientists agreed to fix the value of the speed of light to 299792458 m/s, where m/s is the SI unit of the speed of light. The different methods of measuring the value of c are listed below:

1. Using aberration of light
2. Cavity resonance
3. Interferometry
4. Measuring the time light travels to a mirror at a given distance and back.

Several other methods to derive the value of c are mentioned in the physics laws. One of those methods is by determining the electromagnetic constant’s values and their respective relation with c.

Things to Remember

Below are a few points provided which are important to know more about the value of c or the speed of light.

• The speed of light is a crucial factor in the dynamics of physics.
• It determines various vital laws and classical and quantum physics experiments.
• There is a link between mass and energy with the help of the value of c is known as the equivalence of mass and energy.
• The value of c determines the maximum signal velocity between two objects.

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