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# Refraction

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### Refraction

1. 1. Refraction
2. 2. Refraction <ul><li>Although light travels in straight lines, it bends when it passes from one medium to another </li></ul>Medium (plural “media”) - the material that is being used or undergoing a process
3. 3. Refraction <ul><li>Refraction = the bending of light rays as they pass between two different media </li></ul>
4. 4. Refraction <ul><li>Refraction occurs due to changes in the speed of light in different mediums </li></ul><ul><li>Different media slow down light by different amounts </li></ul><ul><li>The more that light slows down, the more the light is refracted </li></ul>
5. 5. Refraction in Water <ul><li>Light rays change direction at the surface of the water </li></ul><ul><li>The image of the chest appears to be more shallow than the actual chest </li></ul>
6. 6. Speed of Light <ul><li>In a vacuum: </li></ul><ul><li>However, it is impossible for light to move at this speed when particles get in the way… </li></ul>or
7. 7. Refraction <ul><li>The particles in a medium slow down the passage of light waves </li></ul><ul><li>Light only refracts at the boundary when it is entering or leaving a medium </li></ul>
8. 8. Index of Refraction <ul><li>Index of Refraction = the amount by which a transparent medium decreases the speed of light </li></ul>(since units cancel, a refractive index does not have any units) or
9. 10. Given : Speed of light in glass = 1.91 x 10 8 m/s Speed of light in vacuum = 3.00 x 10 8 m/s = 1.57 The refractive index is 1.57 = 3.00 x 10 8 m/s 1.91 x 10 8 m/s
10. 11. Given : Refractive index in water = 1.33 Speed of light in a vacuum = 3.00 x 10 8 m/s v = 2.26 x 10 8 m/s The speed of light in water is 2.26 x 10 8 m/s 1.33 = 3.00 x 10 8 m/s v
11. 12. How Light Refracts <ul><li>The part of the light beam that hits the medium first will slow down first </li></ul>
12. 13. Angle of Refraction <ul><li>low refractive index (e.g. air)  high refractive index (e.g. glass) </li></ul><ul><ul><li>Light bends towards the normal </li></ul></ul><ul><li>The angle of refraction is measured relative to the normal </li></ul>
13. 14. Angle of Refraction <ul><li>high refractive index (e.g. glass)  low refractive index (e.g. air) </li></ul><ul><ul><li>Light bends away from the normal </li></ul></ul>
14. 15. Dispersion <ul><li>The amount of refraction is different for each colour </li></ul><ul><li>A single beam of white light can be split into a rainbow of colours </li></ul><ul><li>Dispersion = the refraction of white light into separate wavelengths (colours) </li></ul>
15. 18. Rainbows
16. 19. Rainbows