When light travels from a less dense medium to a more dense medium, what happens to its speed?

When light travels from a less dense medium, such as air, to a more dense medium, like water or glass, its speed decreases. This phenomenon is due to the way light interacts with the particles in the medium. In a less dense medium, light can move more freely because there are fewer particles to interact with. When it enters a more dense medium, the increased number of particles results in more interactions, thus reducing the speed of light.

The change in speed also affects the wavelength of the light. As light slows down, its wavelength decreases, while its frequency remains constant. This relationship between speed, wavelength, and frequency is fundamental to understanding how light behaves when transitioning between different media.

Overall, when light transitions from a less dense to a more dense medium, the decrease in speed is a consistent observation backed by the principles of optics.