Page 254 - text book form physics kssm 2020

Applications of Total Internal Reflection in Daily Life

Prism periscope
A A z Used to see objects behind a barrier.
z Made up of two right angle prisms fitted at both ends of a long tube.
Object z Light rays from an object travel along the normal to the side AB
B C of the upper prism (pass through the opening of the periscope).
The light rays reach side AC without refraction. The angle of
º
incidence is 45 and is larger than the critical angle of the prism,
º
which is 42 . Therefore, total internal reflection happens at side
AC and the light rays are reflected downwards.
z The reflected light rays travel downwards along the normal to
side DE of the lower prism.
D E Observer
z Once again, the reflected light rays experience total internal
reflection at side DF. Finally, the reflected light rays emerge from
side EF without refraction and enter the eyes of observer. The
Barrier F F Image
of object image formed is upright and of the same size as the object.

Outer cladding
Optical fibre

z Widely used in the fields of telecommunication
and medicine. Inner coreeeeeeeeeerrrrrrrrr r ccccc
z Made from pure glass or plastic fibres.
z Inner core which has a high refractive index is
surrounded by a layer of cladding with a low
refractive index.
z Light signals enter one end of the optic fibre and Inner core has Coating has a low
experience total internal reflection continuously in the a high refractive refractive index
inner core until they reach the other end. As such, index
signals can be sent rapidly without disturbances from
electric signals.
Light signal

Cat’s eye reflector CAREER
Light rays
Total internal enter z Used for the purpose iNFO
refl ection of safety for road users
happens Doctors use endoscope to
Light rays at night. examine the internal organs.
exit z Light rays from car Engineers use fi bre optics to
headlights enter the examine the interior of complex
reflector and experience machines. Communication
total internal reflection on experts use fi bre optics for
the back surface of sending data speedily.
the reflector.

Figure 6.24 Applications of total internal reflection in daily life
248 6.2.3
248
6.2.3