Refraction of light (physics) Flashcards
definition of incident ray
the light ray that hits the reflecting surface
definition of refracted ray
the light ray that enters a medium and undergoes a change of direction
definition of point of incidence
the point at which the incident ray hits the reflecting surface
definition of normal
the imaginary line that is perpendicular to the reflecting surface at the point of incidence
definition of angle of incidence
the angle between the incident ray and the normal
definition of angle of refraction
the angle between the refracted ray and the normal
definition of refractive index
ratio of speed of light in vacuum to speed of light in medium
definition of refraction of light
bending of light as it passes from one medium to another of different optical density
laws of refraction
1: incident ray, refracted ray and the normal at the point of incidence all lie in the same plane
2 (Snell’s Law): For two given media, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant i.e. sin i/sin r = constant
what is total internal reflection
the complete reflection of light inside an optically denser medium at its boundary with an optically less dense medium
when does total internal reflection occur
when an angle of incidence in the glass block is greater then critical angle
ray will be completely reflected off the flat surface of the block
what is critical angle
critical angle is defined as the angle of incidence in an optically denser medium for which the angle of refraction in the optically less dense medium is 90 degrees
conditions for total internal reflection
- incident ray must travel from an optically denser to an optically less dense medium
- the angle of incidence must be greater than the critical angle
applications of total internal reflection
1: Glass prisms (used to reflect light by total internal reflection in some optical instruments e.g. binoculars, periscopes)
Better light reflectors than mirrors because they don’t have a silvered surface that can wear off and produce multiple reflections
2: Optical fibres
rely on total internal reflection of light to transmit signals
e.g. used in endoscope by doctors to inspect the insides of hollow organs e.g. digestive tract
adv of using optical fibres over copper wires in telecommunications
- 10 to 1000x faster
- less signal loss
lighter and cheaper - more info over long distances
- immune electromagnetic interference
adv of optical fibres in medicine
- thin and light (endoscopes kept small for minimally invasive examination and surgery)
- flexible (can curve around obstacles when taking images insdie body)
