The table shows the critical angle for light passing from four transparent materials into air. Material Critical angle / ° Diamond 24 Glass 42 Water 49 Pers...
Question 1 Report
The table shows the critical angle for light passing from four transparent materials into air.
| Material | Critical angle / ° |
|---|---|
| Diamond | 24 |
| Glass | 42 |
| Water | 49 |
| Perspex | 43 |
A ray of light inside each material strikes the boundary at 45° to the normal. In which materials does total internal reflection occur?
Answer Details
Total internal reflection occurs when light inside a material strikes the boundary at an angle greater than the critical angle for that material. The question states that the ray strikes at 45° in each material.
Checking each material against 45°:
- Diamond: critical angle = 24°. Since 45° > 24°, total internal reflection occurs.
- Glass: critical angle = 42°. Since 45° > 42°, total internal reflection occurs.
- Perspex: critical angle = 43°. Since 45° > 43°, total internal reflection occurs.
- Water: critical angle = 49°. Since 45° < 49°, total internal reflection does not occur. The light partially refracts out of the water.
Total internal reflection therefore occurs in diamond, glass, and perspex, but not in water.
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