[physics] refraction

Question 1

laws of refraction

Answer 1

1. incident ray, refracted ray, and normal at the point of incidence all lie on the same plane
2. for the 2 given media, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant

Question 2

conditions of tir

Answer 2

1. incident ray must travel from optically denser to optically less dense medium
2. angle of incidence must be greater than critical angle

Question 3

if from less dense medium to denser medium, speed and bending?

Answer 3

• less dense to denser medium
• slow down
• bend towards normal

Question 4

3 equations to remember

Answer 4

refer to notes

Question 5

larger refractive index slower or faster speed of light

Answer 5

slower

Question 6

applications of tir

Answer 6

1. glass prisms
2. optical fibres (telecommunication, medicine)

Question 7

what is optical fibre

Answer 7

• long, thin and flexible
• made of glass or plastic
• can carry information in the form of coded light pulses

Question 8

what is the use of tir in optical fibres

Answer 8

transmit signals

Question 9

what if the optical fibre becomes bent

Answer 9

light rays entering it will still be internally reflected at the boundary between the 2 refractive materials

Question 10

advantages of using optical fibres over copper wires in telecommunications

Answer 10

1. data transfer rate is ten to thousands times faster
2. less signal loss
3. lighter and cheaper
4. carry much more information over long distances
5. immune to electromagnetic intereference

Question 11

advantages of using optical fibres in medicine

Answer 11

1. thin and light, the endoscopes are kept small for minimally invasive examination and surgery
2. flexible, the endoscopes can curve around obstacles when taking images inside the body

Question 12

why use glass prisms

Answer 12

it is used to reflect light by TIR in some optical instruments like binoculars, periscopes and single lens reflex cameras

Question 13

why use tir for glass prisms

Answer 13

it is a better light reflector than mirrors as they do not
- has a silvered surface that can wear off
- produce multiple reflections