1. Refractive Index:
- The refractive index (n) of a material is a measure of how much light bends when passing through it compared to its speed in a vacuum.
- Glass has a higher refractive index than air, which means light travels slower in glass than in air.
2. Snell's Law:
- Snell's law describes the relationship between the angles of incidence and refraction when light passes from one medium to another. It states that:
```
n1 * sin θ1 = n2 * sin θ2
```
- n1 and n2 are the refractive indices of the first and second media, respectively.
- θ1 and θ2 are the angles of incidence and refraction, respectively.
3. Light Bends toward Normal:
- When light travels from a denser medium (higher refractive index) to a less dense medium (lower refractive index), it bends away from the normal (a line perpendicular to the surface).
4. Speed Change:
- As light bends away from the normal upon entering the less dense medium, its direction changes, and consequently, its speed changes. Since the frequency of light remains constant, a change in direction implies a change in speed.
5. Faster in Air:
- Since glass has a higher refractive index than air, light travels slower in glass. Conversely, when light leaves the glass and enters the air, it encounters a lower refractive index, causing it to bend toward the normal and speed up.
In summary, when light moves from glass to air, its speed increases because the refractive index decreases, resulting in a change in the direction of the light wave as it crosses the boundary between the two media.
