As a domain expert in physics, I can explain the phenomenon you're asking about. When light travels from one medium to another, its speed changes due to the difference in the optical density of the media. This change in speed is what causes the bending of light, a process known as refraction.

Step 1: English Explanation

When light moves from air into water, it experiences a change in its speed. This is because air and water have different refractive indices, which are measures of how much the medium can bend light. The refractive index is directly related to the speed of light in that medium. The speed of light in a vacuum is a universal constant, approximately \(3 \times 10^8\) meters per second. However, when light enters a medium like water, it slows down because water's molecules interact with the light waves, causing them to travel more slowly.

The amount by which light slows down is quantified by the refractive index of water, which is about 1.33. This means that light travels through water at a speed that is about 1.33 times slower than it does in a vacuum. The mathematical relationship between the speed of light in a vacuum (\(c\)), the speed of light in the medium (\(v\)), and the refractive index (\(n\)) is given by the equation:

\[ v = \frac{c}{n} \]

As light enters water, it not only slows down but also changes direction, a phenomenon known as refraction. This bending occurs because the light waves at the leading edge of the beam are slowed down more quickly than those at the trailing edge. This causes the wavefront to tilt towards the normal, which is an imaginary line perpendicular to the surface at the point of incidence. The degree to which the light bends depends on the angle at which it strikes the water and the difference in refractive indices between air and water.

The change in direction can be described by Snell's Law, which relates the angles of incidence and refraction to the refractive indices of the two media. Snell's Law is given by:

\[ n_1 \sin(\theta_1) = n_2 \sin(\theta_2) \]

where \( n_1 \) and \( n_2 \) are the refractive indices of air and water, respectively, and \( \theta_1 \) and \( \theta_2 \) are the angles of incidence and refraction.

In summary, when light passes from air into water, it slows down and changes direction due to the higher refractive index of water. This is the fundamental principle behind many optical phenomena and technologies, including lenses, prisms, and fiber optics.

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What happens is that light slows down when it passes from the less dense air into the denser glass or water. This slowing down of the ray of light also causes the ray of light to change direction. It is the change in the speed of the light that causes refraction.read more >>