refraction

Question 1

describe what must happen for refraction to be occurring

Answer 1

the light passes a boundary between two transparent media. at the boundary, the light rays undergo a change in direction.

Question 2

because of this the direction is being taken as?

Answer 2

the angle from a hypothetical lines called the normal. it is perpendicular to the surface of the boundary and is represented by single straight dotted line therefore

Question 3

however what does the change in direction depend on?

Answer 3

the media the light ray travels between

Question 4

explain when and why light would bend towards the normal

Answer 4

the light ray slowing down as it passes from a less optically dense material to a material that has a greater optical density. for example, when light is travelling but from air to glass.

Question 5

explain when and why light would bend away from the normal

Answer 5

the light ray travelling as it goes from a material with a greater optical density to a material having a lower optical density

Question 6

in which circumstances results in light not bending at all

Answer 6

whenever passing along the perpendicular normal

Question 7

why does the light ray change in direction?

Answer 7

due to the change in speed when travelling in different substances. light passing to a denser substance means rays slow down and therefore bend towards the normal. the greater the optical density of a material, the more light is slowing down when entering it.

Question 8

properties that change due to refraction

Answer 8

the speed and wavelength NOT frequency
technically the intensity and amplitude of the wave additionally decreases slightly upon refraction since a somewhat small portion of it reflects but this is not as noticeable as the change in speed and the wavelength therefore

Question 9

define what is meant by the refractive index of a substance

Answer 9

the refractive index is a property of a material which measures how much light has the ability to slow down when passing through it.

Question 10

can you state the letters used to represent the refractive index?

Answer 10

n

Question 11

the equation used to calculate the refractive index?

Answer 11

n (refractive index) = c / cs
c = speed of light in a vaccum (ms^-1)
cs = speed of light in a substance (ms^-1)

Question 12

how does the refractive index of a substance impact speed the light is travelling at?

Answer 12

light travels but at different speeds within different substances depending on their refractive index
a material with a higher refractive index is called optically dense, a material similar therefore causes light to slow down as it enters

Question 13

the word to describe light with a high refractive index

Answer 13

optically dense

Question 14

why is the value of n always greater than 1 therefore?

Answer 14

the speed of light in a substance will always be less compared to the speed of light in a vaccum.

Question 15

the refractive index of air and why?

Answer 15

the refractive index of air can be taken to be approximately 1 it is because light whenever travelling through air doesnt slow so significantly down therefore

Question 16

define Snell’s Law

Answer 16

it relates the angle of incidence to the angle of refraction

Question 17

equation Snell’s Law

Answer 17

n1sinpheta1 = n2sinpheta2c
n1 = the refractive index of material 1 therefore
n2 = the refractive index of material 2 therefore
pheta1 = the angle of incidence of the ray in material 1 so
pheta2 = the angle of refraction of the ray in material 2 so
c = speed of light

Question 18

how should you figure out which parts of the equation go?

Answer 18

pheta1 and pheta2 are always being therefore taken but instead from the normal so
Material 1 is always the material in which the ray goes through at first so .
Material 2 is always the material in which the ray goes through at second so

Question 19

if the angle of incidence is increased what happens?

Answer 19

the angle of refraction further increases until it gets closer to about 90 degrees approximately therefore so as

Question 20

describe what happens if the angle of refraction is exactly about 90 degrees to the right therefore

Answer 20

the light is refracted along the boundary
As the angle of incidence is increased, the angle of refraction also increases until it gets closer to about 90 degrees. however whenever the angle of refraction is exactly 90 and the light is refracted along the boundary, the angle of incidence has reached the critical angle therefore so as
at this point, the angle of incidence is known as the critical angle phetac therefore.

Question 21

the equation used to calculate the critical angle?

Answer 21

sin phetac = n2 / n1

Question 22

how can this equation be derived from Snell’s Law?

Answer 22

pheta1 = critical angle
pheta2 is equivalent to 90 degrees therefore so
n1 greater compared to n2

Question 23

define what is meant by Total Internal Reflection

Answer 23

angle of incidence is greater compared to the critical angle and the incident refractive index called n1 is greater compared to the refractive index of the material at the boundary n2

Question 24

the two conditions necessary for Total Internal Reflection

Answer 24

angle of incidence is greater than the critical therefore so angle
the refractive index therefore is n1 greater than the refractive index n2 therefore

Question 25

why do diamonds sparkle loads?

Answer 25

diamond has high refractive index of (2.4) giving it therefore a low critical angle so light internally reflected multiple times before emerges. the diamond disperses light to colours

Question 26

define optical fibres

Answer 26

an optical fibre is a really flexible thin tube of glass or plastic fibre that utilises the phenomenon of total internal reflection to send light signals having really high speed therefore so
the signals are sending but over large distances and in addition to round corners

Question 27

the uses of optical fibres

Answer 27

• communications, for example for telephone and internet transmission
• medical imaging; endoscopes

Question 28

explain what a stepindex optical fibre is

Answer 28

the optical fibre has reasonably high refractive index but are surrounded by cladding w lower refractive index to allow totals internal reflection

Question 29

how do stepindex optical fibres work therefore?

Answer 29

Light is also shone in at one end of the fibre. Fibre so narrow meaning the light always therefore hits the boundary between the fibre and cladding at an angle bigger than the critical angle therefore. So all the light is totally internally reflected from boundary to boundary until it reaches the other end.

Question 30

the so three main components making up optical fibres

Answer 30

• An optically dense cores for example plastic/glass therefore.
• A lower optical density cladding surrounding the core and an outer sheath.