| what is meant by refraction | the property of waves in which the waves change speed when passing from one material to another material; this can also result in a change in direction of the wave |
| what is a 'normal' | a dotted line drawn perpendicular to the surface of the refracting materials, at the point of the entry of the light |
| what happens when light travels from air to a denser medium | it will refract toward the normal, light wave slows and the angle of refraction is smaller than the angle of incidence |
| what happens when light travels from a denser medium into air | it will refract away from the normal, light wave speeds up and the angle of refraction is bigger than the angle of incidence |
| describe what happens during refraction from air into glass when the angle of incidence = 0 | the wave slows and its wavelength decreases as it enters the glass
as it returns to air, its speed and wavelength increase to their original values |
| describe what happens during refraction from air into glass when the angle of incidence is greater than 0 | if the light ray meets a glass block at an angle (where angle of incidence is greater than 0) the wave slows down and refracts towards the normal
the ray returns to its original direction and speed as it leaves the block |
| what is the angle of incidence | the angle between the normal and the incident ray of light |
| what is the angle of refraction | the angle between the refracted ray of light and the normal |
| what is an optical fibre | a thin strand of high quality glass. light can be transmitted through it over very large distances |
| what happens to angle of refraction when angle of incidence increases | angle of refraction increases
will increase to a point at which the light ray leaves the material at exactly 90 degrees |
| what is meant by critical angle | the minimum angle at which total internal reflection occurs |
| when does total internal reflection occur? | at any angle greater than the critical angle total internal reflection occurs and the light ray obeys the normal rules for reflection (ie, angle of incidence=angle of refraction) |
| what is total internal reflection | process by which a light ray is reflected off the inside of a material rather than being refracted to the outside |
| describe what happens when the angle of incidence is increased past the critical angle | the ray doesn't exit glass into air but is reflected inside the glass. As none of the light refracts into air, the light ray has been totally internally reflected inside the material |
| what are practical uses of optical fibres | used in telecommunications because they can carry enormous amounts of information in light pulses trapped inside of them. This information is carried at a very high speed along an optical fibre cable. |
