When visible light travels through thick glass or water, it does experience certain changes in its behavior, including changes in speed, wavelength, and direction. These changes are a result of the interaction between light and the medium it is passing through.
Speed: Light slows down when it enters a denser medium like glass or water. The speed of light in a vacuum is about 299,792 kilometers per second, but it slows down to about 225,000 kilometers per second in glass and around 225,000 kilometers per second in water. This decrease in speed is due to the increased interaction between light and the atoms or molecules of the medium, which causes a delay in the light's propagation.
Wavelength: The wavelength of light also changes as it passes through a medium. When light enters a denser medium, such as glass or water, its wavelength decreases. This phenomenon is known as wavelength-dependent refraction or dispersion. Different wavelengths of light bend to different extents as they pass from one medium to another. This bending or change in direction of light is responsible for the separation of colors in a prism or the formation of rainbows.
Frequency: The frequency of light, which determines its color, remains constant as it passes through a medium. Since the speed of light changes in a different medium, and the frequency remains the same, the product of frequency and wavelength (speed) must remain constant according to the equation c = λν, where c is the speed of light, λ is the wavelength, and ν is the frequency.
In summary, when visible light travels through thick glass or water, it slows down, its wavelength decreases, but its frequency remains the same. These changes occur due to the interaction between light and the atoms or molecules of the medium, leading to phenomena such as refraction and dispersion.