No, the frequency of light does not decrease, and the wavelength does not increase when light travels through a vacuum for a long time. In a vacuum, light travels at a constant speed known as the speed of light, denoted by "c" (approximately 299,792 kilometers per second or 186,282 miles per second).
According to the wave equation, the speed of light (c) is equal to the product of the wavelength (λ) and the frequency (f) of the light:
c = λ * f
Since the speed of light in a vacuum is constant, any change in the wavelength of light must be accompanied by an equivalent change in frequency, ensuring that the product remains constant. This relationship between wavelength and frequency is known as the wave's dispersion. Therefore, as light travels through a vacuum, its frequency and wavelength remain unchanged over time.
However, it's worth noting that light can interact with various media, such as gases, liquids, or solids, where its speed may change, resulting in phenomena like refraction. But in a vacuum, light maintains a constant speed, frequency, and wavelength.