3. Refraction of Light

Question 1

define refraction

Answer 1

chane in driection of light when is passess from one transparent medium into another of different optical density

Question 2

what impacts the velocity of light

Answer 2

density of the medium it travels through

Question 3

denser medium

Answer 3

slower light

Question 4

what happens when a beam of light strikes a more dense medium obliquelys

Answer 4

edge of a beam which arrives first is slowed down when entering the medium
the other side continues at the same speed
when the other side hits the medium it is deviated towars the normal as it enters

Question 5

Optical density

Answer 5

comparison of velocity of light in a vacuum vs in the medium

Question 6

what is the measurement of optical density

Answer 6

measurement - absolute refractive index (n) of the medium

Question 7

absolute refractive index =

Answer 7

velocity of light in a vacuum / velocity of light in medium

Question 8

air and vacuum with the refractive index

Answer 8

as optical density in air as a medium is neglible under normal conditions
air = vacuum

Question 9

refractive index of air

Answer 9

1

Question 10

refractive index of water (incl aqeuous)

Answer 10

1.33

Question 11

refractive index of cornea

Answer 11

1.37

Question 12

refractive index of crystallinelens

Answer 12

1.386 - 1.406

Question 13

refractive index of crown glass

Answer 13

1.52

Question 14

refractive index of flint glass

Answer 14

1.6

Question 15

refractive index of diamond

Answer 15

2.5

Question 16

how can you measure refractive index

Answer 16

using a refractometer

Question 17

on entering an optically dense medium from a less dense medium

Answer 17

light is deviated towards the normal

Question 18

what governs / influences the angle of incidence and reflection

Answer 18

refractive indices of the media according to Snell’s law

Question 19

Snell’s law

Answer 19

incident ray, refracted ray and normal all lie in the same plan
angles of incidence and refraction are related to the refractive index of the media

Question 20

Snell’s law equation

Answer 20

medium1x n x medium 2 = sin i / sin R

where n is the refractive index

Question 21

Snell’s law equation in air to glass

Answer 21

air x N x glass = sin i / sin r

Question 22

if the interface is between two denser mediums (glass and air) then the value of n for that interface can be calculated b

Answer 22

water N glass = n glass / n water

Question 23

if passing from medium 1 to medium 2 the index of refraction can be given by

Answer 23

1n2 = n2 / n1

Question 24

What happens when light passes air -> glass -> air

Answer 24

Air -> glass = deviated towards the normal

glass -> = deviated away from the normal

BUT overall it is laterally displaced

Question 25

light passing across a curved interface between two media of different refractive indices

Answer 25

obeys snell's law

Question 26

a convex spherical cruved surface

Answer 26

causes parallel light to conver or diverege

Question 27

convex curved surface cause CONVERGENCE if

Answer 27

n1 < n2 if the media passing to is greater than from e.g. air : cornea

Question 28

convex curved surface cause DIVERGENCE if

Answer 28

n1 > n2 if the media passing to is LESS than from e.g. glass : air

Question 29

refracting power of a surface formula

Answer 29

surface power = (n2-n1) / r where r is the radius of the curvature of the surface in METRES

Question 30

what is refracting power measured in

Answer 30

dioptres

Question 31

surface power is positive for

Answer 31

converging surfaces

Question 32

surgace power is negative for

Answer 32

diverging surfaces

Question 33

example of a refracting surface

Answer 33

anterior surface of the cornea

Question 34

objects situated in an optically dense mediua appear

Answer 34

displaced when viewed from a less dense medium this is due to refraction

Question 35

What happens to rays emerging from a denser medium

Answer 35

1. strike at 90 degree and leave undeviated 2. strike at less than 90 degree and are refracted 3. meets at the citical angle and run parallel with the inferface 4. less than critical angle and are internally reflectid

Question 36

how is the critical angle determined

Answer 36

by the refractive indcies of thhe media and can be calculated using Snell's law

Question 37

critical angle for tear film / air interface

Answer 37

48.5 degrees

Question 38

critical angle for crown glass / air interface

Answer 38

41

Question 39

example of how total internal refleciton is used pratically

Answer 39

fibre opitc cables

Question 40

what prevents visulation of the angle of the anterior chamber and peripheral retina

Answer 40

total internal reflection

Question 41

how to overcome total internal reflection when examining the ey

Answer 41

use a contact lens that has a HIGHER refractive indice than the eye and filling the space between the eye and the lens changes the refracting surface to allow visulaision of the angle of the anterior chamber

Question 42

dispersion of light

Answer 42

light of shorter waves are deviated more than longer blue more than red

Question 43

dispersive power

Answer 43

indicate by the anlge formed between red and blue light leaving (with yellow in betwee)

Question 44

dispersive power and refractive index

Answer 44

are NOT related