uses of optical fibres in medicine
light travels down optical fibres into or out of body:
TO examine internal organ
light travels both ways into and out of body
TO destroy (cancerous cells)
by heating them
OR used in endoscope (bundle of fibres)
which is put into body to view internal organ OR for keyhole surgery
conditions for TIR
incident ray from optically dense medium
angle of incidence greater than critical angle
no light refracted
reflected with i=r
describe what is meant by transverse wave motion
transmission of energy (through medium) AND no transfer of energy;
direction of vibration of particles;
perpendicular to direction to energy travel/wave/propagation;
slowing of light in terms of wavefronts
one side of wavefront slows down before other side;
wavefront slews around OR bends at boundary;
bends towards the normal OR bends towards the side that slows first;
why X-rays okay for patient but dentist needs to be shielded
patient rarely exposed
low total dose on patient
meaningful comment about benefit outweighs danger
dentist frequently exposed
total dose on dentist will be high if not shielded
optical fibres in communication tech
information/message/sound/signal/data encoded as pulses of light is sent through
fibre;
light (or IR radiation) travels along fibre;
light detected at far end or message decoded or total internal reflection mentioned;
what happens when incident ray increases the angle of incidence to critical
angle
angle (form normal) of refraction increases
refracted ray travels along boundary OR reflected ray becomes brighter
critical angle reached
light reflects back into glass with i = r
use of optical fibres
to carry telephone signals;
medical diagnosis/imaging;
