 Refraction
Definition: Refraction is the bending of light as it passes from one transparent medium to another.
- This bending of light is due to a change in the velocity of light as it travels through materials of different optical densities.
- The more optically dense the medium the slower light travels.
- For refraction to occur the incident angle must be at an angle other than 90 o.
- Light travels fastest in a vacuum at 3 x 10 8m/s or
300 000 km/s.
Laws of refraction
- An incident ray along the normal is not refracted (though there is a change in velocity).
- An incident ray (at an angle other than 90 o) passing from an optically more dense medium to a less dense is refracted away from the normal. (MLA)
- An incident ray (at an angle other than 90 o) passing from an optically less dense medium to a more dense is refracted towards the normal. (LMT)
Note :
- You should be able to identify the incident angle, refracted angle, incident ray and refracted ray. Note some light is also reflected off any surface.
- You should be able to complete ray diagrams when light is travelling from one medium to another.
- Gven the refraction of a ray from one medium to another, you should be able to determine the relative optical densities and also the relative speeds of light in the two materials.
Refraction of light through a rectangular Prism
- Read Text pages 93, 94 and 96. Refer to booklet pages 6 and 7.
- Complete questions in the text book Page 94 and page 97.
- Complete questions in the Light Booklet pages 8 - 10.
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