refraction of light

Question 1

define refraction

Answer 1

refraction is the bending of light as it passes from one medium to another medium of different optical density.

Question 2

define refractive index

Answer 2

refractive index is the ratio of the speed of light in vacuum to the speed of light in the medium.

Question 3

the larger the refractive index, the (higher / lower) the speed of light?

Answer 3

lower.

Question 4

the larger the refractive index, the (larger / smaller) the bending of light.

Answer 4

larger.

Question 5

what is the first law of refraction?

Answer 5

the incident ray, refracted ray and the normal at the point of incidence all lie on the same plane.

Question 6

what is the second law of refraction (aka. Snell’s law)?

Answer 6

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.

Question 7

how do you write out the general Snell’s law?

Answer 7

sin theta1 / sin theta2 = n2 / n1

Question 8

what is the manipulated equation of the Snell’s law?

Answer 8

n1 x sin theta1 = n2 x sin theta2

Question 9

when will total internal reflection occur?

Answer 9

it will occur when the angle of incidence in the glass block is greater than the critical angle theta(c).

Question 10

define critical angle

Answer 10

critical angle theta(c) is the angle of incidence in a optically denser medium for which the angle of refraction in the optically less dense medium is 90 degrees.

Question 11

what is the equation to calculate critical angle?

Answer 11

assuming light is travelling from medium to air,
before manipulation:
sin theta(c) / sin 90 = 1 / n(medium)

after manipulation:
sin theta(c) = 1 / n(medium) OR n(medium) = 1 / sin theta(c)

Question 12

what are the two conditions for total internal reflection?

Answer 12

1. the incident ray must travel from an optically denser to an optically less dense medium.
2. the angle of incidence must be greater than the critical angle theta(c).

Question 13

why are optical fibres relied on to transmit signals?

Answer 13

even when the fibre is bent, light rays entering the will be internally reflected at the boundary between the two refractive materials. this total internal reflection of light will transmit signals.

Question 14

what are the five advantages of using optical fibres over copper wires in telecommunication?

Answer 14

1. the DATA TRANSFER RATE is ten to thousands of times faster.
2. there is LESS SIGNAL LOSS.
3. optical fibres are LIGHTER and CHEAPER.
4. optical fibres can carry MUCH MORE INFORMATION over LONG DISTANCES.
5. optical fibres are IMMUNE to ELECTROMAGNETIC INTERFERENCE (eg. radio transmitters).

Question 15

what are the two advantages of using optical fibres in medicine?

Answer 15

1. optical fibres are THIN and LIGHT. endoscopes are kept small for minimally invasive examination and surgery.
2. optical fibres are FLEXIBLE. endoscopes can curve around obstacles when taking images inside the body.