1. The Nature of Light:
* Wave Nature: Light behaves as a wave, with crests and troughs.
* Speed of Light: The speed of light changes depending on the medium it travels through. Light travels faster in air than in water.
2. Refraction:
* Definition: Refraction is the bending of light as it passes from one medium to another.
* Cause: The change in the speed of light is the primary reason for refraction. When light enters a denser medium (like water), it slows down.
3. Snell's Law:
* Mathematical Description: Snell's Law describes the relationship between the angle of incidence (angle at which light hits the surface), the angle of refraction (angle at which light bends in the new medium), and the indices of refraction of the two media.
* Key Point: The angle of refraction is smaller than the angle of incidence when light enters a denser medium.
4. Explanation:
* Imagine a Light Wave: Picture a light wave approaching the water surface at an angle. The part of the wave that enters the water first slows down, while the part still in the air continues at a faster speed. This difference in speed causes the wave to bend towards the normal.
* Normal: The normal is an imaginary line perpendicular to the surface at the point where the light ray hits.
* Bending Towards the Normal: The slower speed of light in water causes the wavefront to bend towards the normal, making the angle of refraction smaller than the angle of incidence.
In Summary:
The bending of light towards the normal when it enters water from air is due to the change in the speed of light as it passes from a less dense medium (air) to a denser medium (water). This change in speed causes the light wave to bend, following the principles described by Snell's Law.
