Here's the detailed explanation of what causes refraction:
1. Change in Wave Speed:
When a wave moves from one medium to another, its speed changes. This change in speed occurs because the wave interacts differently with the particles of the new medium. In general, waves travel faster in denser media and slower in less dense media.
2. Snell's Law:
The bending of waves due to refraction is governed by Snell's Law, which describes the relationship between the incident angle (the angle at which the wave strikes the boundary) and the refracted angle (the angle at which the wave continues after passing the boundary). Snell's Law states that the ratio of the sines of the incident angle (θ1) and the refracted angle (θ2) is equal to the ratio of the wave speeds in the two media (v1 and v2):
```
sin(θ1) / sin(θ2) = v1 / v2
```
- As the wave crosses the boundary, the part of the wave that enters the second medium slows down, while the part that remains in the first medium continues at its original speed.
- This difference in speed creates a change in the direction of the wavefront, causing it to bend or refract.
3. Index of Refraction:
The index of refraction (n) of a material is a measure of how much it bends light. It is defined as the ratio of the speed of light in a vacuum (c) to the speed of light in the material (v):
```
n = c / v
```
- Materials with a higher index of refraction bend light more than materials with a lower index of refraction.
4. Examples of Refraction:
- Water: When light travels from air into water, it bends toward the normal (the perpendicular line to the surface) because water has a higher index of refraction than air. This is why objects appear to be closer to the surface when viewed from underwater.
- Glass: When light travels from air into glass, it also bends toward the normal because glass has a higher index of refraction than air. This is why objects appear to be magnified when viewed through a glass lens.
- Prisms: Prisms are triangular-shaped objects made of glass or other transparent materials that use refraction to separate light into its component colors. When white light passes through a prism, it bends differently for each color, creating a rainbow effect.
