The velocity of a photon, which is a fundamental particle of light, is always constant in a vacuum and is denoted by the symbol "c," which represents the speed of light in a vacuum. The speed of light in a vacuum is approximately 299,792,458 meters per second (or about 186,282 miles per second).
The constancy of the velocity of light, regardless of its wavelength or frequency, is a fundamental principle in physics known as the speed of light postulate. This postulate is a cornerstone of Albert Einstein's theory of special relativity, which revolutionized our understanding of space and time.
According to special relativity, the speed of light in a vacuum is the same for all observers, regardless of their relative motion or the source of light. This means that regardless of the wavelength (or equivalently, the frequency) of light, all photons travel at the same speed, c.
It is important to note that while the velocity of light is constant, the wavelength and frequency of light are inversely proportional to each other. This relationship is described by the equation c = λν, where c is the speed of light, λ (lambda) is the wavelength, and ν (nu) is the frequency. As the wavelength increases, the frequency decreases, and vice versa. However, the product of the wavelength and frequency always remains constant at the speed of light.