DEFINITIONS: GEOMETRICAL OPTICS 2

1. When Light travels from ...      (MIX)
   When light travels from a rarer to a denser medium it is refracted towards the normal.
   When light travels from a denser to a rarer medium it is refracted away from the normal.
   
   
2. The Laws of Refraction of Light     (MIX)
   1st Law: The incident ray, the normal ray at the point of incidence and the refracted ray all lie in the same plane.
   2nd Law: The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant.
   i.e. , where n is a constant
   
   
3. Refractive Index of a Medium      (MIX)
   The refractive index of a medium is the ratio of the sine of the angle of incidence to the sine of the angle of refraction
   when light travels from a vacuum into that medium.
   
   
4. The Refractive Index Between Two Media      (MIX)
   The refractive index between two media is the ratio of the sine of the angle of incidence to the sine of the angle of refraction
   when light travels from one of those media into the other.
   
   
5. Critical Angle     (MIX)
   When light travels from a denser to a rarer medium
   the angle of incidence whose corresponding angle of refraction is 90°
   is called the critical angle (C) for those two media.
   
   
6. Total Internal Reflection     (MIX)
   When light going from a denser to a rarer medium
   strikes the second medium with an angle of incidence greater than the critical angle,
   it does not enter the second medium.
   It is reflected back into the denser medium. This is called total internal reflection.
   
   
7. Optical Fibre     (MIX)
   A very thin transparent rod (usually of glass) through which light can travel
   by total internal reflection is called an optical fibre.
   
   
8. For a Convex Lens     (MIX)
   If the object is outside the focus the image is real and
   located at the opposite side of the lens to the object.
   The image is inverted.
   
   If the object is inside the focus the image is virtual and
   is located at the same side of the lens as the object.
   The image is upright (erect).