Snellrsquos Law Book page 110 and 112

Syllabus 318 319

16052016

copycgrahamphysicscom 2016

Match the words to the objects

Mirror

Stained Glass

Fibre optics absorbs

emits refracts

reflects

diffracts

transmits

disperses

Totally internally reflects

16052016 copycgrahamphysicscom 2016

What are the properties of reflection refraction and diffraction

Starter copy out and complete the gaps

i The change of the direction of a light ray when it enters a glass block from air is an example of _________

ii The spreading of waves when they pass through a gap is an example of ___________

iii The image of an object seen in a mirror is formed because the mirror causes light from the object to undergo ___________

Key words reflection refraction diffraction

A Long radio waves can bend around obstacles such as hills B Your remote control will still work if you point it away from the TV

towards a flat sold object eg a plate C The bottom of a swimming pool looks nearer than it actually is

16052016 copycgrahamphysicscom 2016

What are the properties of reflection refraction and diffraction

Starter copy out and complete the gaps

i The change of the direction of a light ray when it enters a glass

block from air is an example of refraction ii The spreading of waves when they pass through a gap is an

example of diffraction iii The image of an object seen in a mirror is formed because the

mirror causes light from the object to undergo reflection

A Long radio waves can bend around

obstacles such as hills diffraction B Your remote control will still work if you

point it away from the TV towards a flat

sold object eg a plate reflection

C The bottom of a swimming pool looks

nearer than it actually is refraction

6 16 or 26 = RED 36 or 46 = YELLOW 56 or 66 = GREEN

16052016 copycgrahamphysicscom 2016

Aim bull Describe experiments to investigate the refractive index

bull Know and use Snellrsquos law

bull Know the effect the medium has on the light waves traveling through it

Key words

bull Refractive index

bull Snellrsquos Law

16052016 copycgrahamphysicscom 2016

The big picture

Have you ever wondered

Can reflection and refraction effects save lives

Diabetic eye disease

Eye cancer 16052016 copycgrahamphysicscom 2016

Changing Speed

When light rays enter a

more optically dense

medium

bull Speed decreases

bull Wavelength decreases

bull Frequency remains

constant

bull Light ray bends towards

the normal

hellipcontinued

When light rays enter a

less optically dense

medium

bull Speed increases

bull Wavelength increases

bull Frequency remains

constant

bull Light ray bends away from

the normal

hellipcontinued

When light rays

enters a medium of

different optical

density along the

normal - it does not

change direction

Links What is the link between angle of incidence and

angle of reflection

What property of the glass block will determine how

much the light is refracted

n = sin i

sin r

Sine of the angle

of incidence

Sine of the angle

of refraction Refractive

Index

16052016 copycgrahamphysicscom 2016

How can you find the index of refraction experimentally

bull This is a common exam questions

bull You need to describe exactly what you do

16052016 copycgrahamphysicscom 2016

Answer Practical questions on experiments mustshellip

You must discuss 1 What you would change (independent variable) what you

would measure (dependent variable) 2 What instruments would you use and how would you use

them How would you use them carefully 3 Plot these results on a graph What does the gradient give 4 What would you repeat and why 5 Mention several precautions you will make so that the

results are as accurate as possible

16052016 copycgrahamphysicscom 2016

Method bull Determining Refractive Index Experiment bull Draw around the glass block bull Mark positions of incident and emerging rays using a pencil

or two pins bull Remove block and draw refracted ray inside the rectangle bull Measure the incident angle i between the incident ray and

the normal bull Measure the refracted angle between the refracted ray r

and the normal bull Measure the same two angles for different angles of

incidence

16052016 copycgrahamphysicscom 2016

Match the words to the objects

Mirror

Stained Glass

Fibre optics absorbs

emits refracts

reflects

diffracts

transmits

disperses

Totally internally reflects

16052016 copycgrahamphysicscom 2016

What are the properties of reflection refraction and diffraction

Starter copy out and complete the gaps

i The change of the direction of a light ray when it enters a glass block from air is an example of _________

ii The spreading of waves when they pass through a gap is an example of ___________

iii The image of an object seen in a mirror is formed because the mirror causes light from the object to undergo ___________

Key words reflection refraction diffraction

A Long radio waves can bend around obstacles such as hills B Your remote control will still work if you point it away from the TV

towards a flat sold object eg a plate C The bottom of a swimming pool looks nearer than it actually is

16052016 copycgrahamphysicscom 2016

What are the properties of reflection refraction and diffraction

Starter copy out and complete the gaps

i The change of the direction of a light ray when it enters a glass

block from air is an example of refraction ii The spreading of waves when they pass through a gap is an

example of diffraction iii The image of an object seen in a mirror is formed because the

mirror causes light from the object to undergo reflection

A Long radio waves can bend around

obstacles such as hills diffraction B Your remote control will still work if you

point it away from the TV towards a flat

sold object eg a plate reflection

C The bottom of a swimming pool looks

nearer than it actually is refraction

6 16 or 26 = RED 36 or 46 = YELLOW 56 or 66 = GREEN

16052016 copycgrahamphysicscom 2016

Aim bull Describe experiments to investigate the refractive index

bull Know and use Snellrsquos law

bull Know the effect the medium has on the light waves traveling through it

Key words

bull Refractive index

bull Snellrsquos Law

16052016 copycgrahamphysicscom 2016

The big picture

Have you ever wondered

Can reflection and refraction effects save lives

Diabetic eye disease

Eye cancer 16052016 copycgrahamphysicscom 2016

Changing Speed

When light rays enter a

more optically dense

medium

bull Speed decreases

bull Wavelength decreases

bull Frequency remains

constant

bull Light ray bends towards

the normal

hellipcontinued

When light rays enter a

less optically dense

medium

bull Speed increases

bull Wavelength increases

bull Frequency remains

constant

bull Light ray bends away from

the normal

hellipcontinued

When light rays

enters a medium of

different optical

density along the

normal - it does not

change direction

Links What is the link between angle of incidence and

angle of reflection

What property of the glass block will determine how

much the light is refracted

n = sin i

sin r

Sine of the angle

of incidence

Sine of the angle

of refraction Refractive

Index

16052016 copycgrahamphysicscom 2016

How can you find the index of refraction experimentally

bull This is a common exam questions

bull You need to describe exactly what you do

16052016 copycgrahamphysicscom 2016

Answer Practical questions on experiments mustshellip

You must discuss 1 What you would change (independent variable) what you

would measure (dependent variable) 2 What instruments would you use and how would you use

them How would you use them carefully 3 Plot these results on a graph What does the gradient give 4 What would you repeat and why 5 Mention several precautions you will make so that the

results are as accurate as possible

16052016 copycgrahamphysicscom 2016

Method bull Determining Refractive Index Experiment bull Draw around the glass block bull Mark positions of incident and emerging rays using a pencil

or two pins bull Remove block and draw refracted ray inside the rectangle bull Measure the incident angle i between the incident ray and

the normal bull Measure the refracted angle between the refracted ray r

and the normal bull Measure the same two angles for different angles of

incidence

16052016 copycgrahamphysicscom 2016

What are the properties of reflection refraction and diffraction

Starter copy out and complete the gaps

i The change of the direction of a light ray when it enters a glass block from air is an example of _________

ii The spreading of waves when they pass through a gap is an example of ___________

iii The image of an object seen in a mirror is formed because the mirror causes light from the object to undergo ___________

Key words reflection refraction diffraction

A Long radio waves can bend around obstacles such as hills B Your remote control will still work if you point it away from the TV

towards a flat sold object eg a plate C The bottom of a swimming pool looks nearer than it actually is

16052016 copycgrahamphysicscom 2016

What are the properties of reflection refraction and diffraction

Starter copy out and complete the gaps

i The change of the direction of a light ray when it enters a glass

block from air is an example of refraction ii The spreading of waves when they pass through a gap is an

example of diffraction iii The image of an object seen in a mirror is formed because the

mirror causes light from the object to undergo reflection

A Long radio waves can bend around

obstacles such as hills diffraction B Your remote control will still work if you

point it away from the TV towards a flat

sold object eg a plate reflection

C The bottom of a swimming pool looks

nearer than it actually is refraction

6 16 or 26 = RED 36 or 46 = YELLOW 56 or 66 = GREEN

16052016 copycgrahamphysicscom 2016

Aim bull Describe experiments to investigate the refractive index

bull Know and use Snellrsquos law

bull Know the effect the medium has on the light waves traveling through it

Key words

bull Refractive index

bull Snellrsquos Law

16052016 copycgrahamphysicscom 2016

The big picture

Have you ever wondered

Can reflection and refraction effects save lives

Diabetic eye disease

Eye cancer 16052016 copycgrahamphysicscom 2016

Changing Speed

When light rays enter a

more optically dense

medium

bull Speed decreases

bull Wavelength decreases

bull Frequency remains

constant

bull Light ray bends towards

the normal

hellipcontinued

When light rays enter a

less optically dense

medium

bull Speed increases

bull Wavelength increases

bull Frequency remains

constant

bull Light ray bends away from

the normal

hellipcontinued

When light rays

enters a medium of

different optical

density along the

normal - it does not

change direction

Links What is the link between angle of incidence and

angle of reflection

What property of the glass block will determine how

much the light is refracted

n = sin i

sin r

Sine of the angle

of incidence

Sine of the angle

of refraction Refractive

Index

16052016 copycgrahamphysicscom 2016

How can you find the index of refraction experimentally

bull This is a common exam questions

bull You need to describe exactly what you do

16052016 copycgrahamphysicscom 2016

Answer Practical questions on experiments mustshellip

You must discuss 1 What you would change (independent variable) what you

would measure (dependent variable) 2 What instruments would you use and how would you use

them How would you use them carefully 3 Plot these results on a graph What does the gradient give 4 What would you repeat and why 5 Mention several precautions you will make so that the

results are as accurate as possible

16052016 copycgrahamphysicscom 2016

Method bull Determining Refractive Index Experiment bull Draw around the glass block bull Mark positions of incident and emerging rays using a pencil

or two pins bull Remove block and draw refracted ray inside the rectangle bull Measure the incident angle i between the incident ray and

the normal bull Measure the refracted angle between the refracted ray r

and the normal bull Measure the same two angles for different angles of

incidence

16052016 copycgrahamphysicscom 2016

What are the properties of reflection refraction and diffraction

Starter copy out and complete the gaps

i The change of the direction of a light ray when it enters a glass

block from air is an example of refraction ii The spreading of waves when they pass through a gap is an

example of diffraction iii The image of an object seen in a mirror is formed because the

mirror causes light from the object to undergo reflection

A Long radio waves can bend around

obstacles such as hills diffraction B Your remote control will still work if you

point it away from the TV towards a flat

sold object eg a plate reflection

C The bottom of a swimming pool looks

nearer than it actually is refraction

6 16 or 26 = RED 36 or 46 = YELLOW 56 or 66 = GREEN

16052016 copycgrahamphysicscom 2016

Aim bull Describe experiments to investigate the refractive index

bull Know and use Snellrsquos law

bull Know the effect the medium has on the light waves traveling through it

Key words

bull Refractive index

bull Snellrsquos Law

16052016 copycgrahamphysicscom 2016

The big picture

Have you ever wondered

Can reflection and refraction effects save lives

Diabetic eye disease

Eye cancer 16052016 copycgrahamphysicscom 2016

Changing Speed

When light rays enter a

more optically dense

medium

bull Speed decreases

bull Wavelength decreases

bull Frequency remains

constant

bull Light ray bends towards

the normal

hellipcontinued

When light rays enter a

less optically dense

medium

bull Speed increases

bull Wavelength increases

bull Frequency remains

constant

bull Light ray bends away from

the normal

hellipcontinued

When light rays

enters a medium of

different optical

density along the

normal - it does not

change direction

Links What is the link between angle of incidence and

angle of reflection

What property of the glass block will determine how

much the light is refracted

n = sin i

sin r

Sine of the angle

of incidence

Sine of the angle

of refraction Refractive

Index

16052016 copycgrahamphysicscom 2016

How can you find the index of refraction experimentally

bull This is a common exam questions

bull You need to describe exactly what you do

16052016 copycgrahamphysicscom 2016

Answer Practical questions on experiments mustshellip

You must discuss 1 What you would change (independent variable) what you

would measure (dependent variable) 2 What instruments would you use and how would you use

them How would you use them carefully 3 Plot these results on a graph What does the gradient give 4 What would you repeat and why 5 Mention several precautions you will make so that the

results are as accurate as possible

16052016 copycgrahamphysicscom 2016

Method bull Determining Refractive Index Experiment bull Draw around the glass block bull Mark positions of incident and emerging rays using a pencil

or two pins bull Remove block and draw refracted ray inside the rectangle bull Measure the incident angle i between the incident ray and

the normal bull Measure the refracted angle between the refracted ray r

and the normal bull Measure the same two angles for different angles of

incidence

16052016 copycgrahamphysicscom 2016

Aim bull Describe experiments to investigate the refractive index

bull Know and use Snellrsquos law

bull Know the effect the medium has on the light waves traveling through it

Key words

bull Refractive index

bull Snellrsquos Law

16052016 copycgrahamphysicscom 2016

The big picture

Have you ever wondered

Can reflection and refraction effects save lives

Diabetic eye disease

Eye cancer 16052016 copycgrahamphysicscom 2016

Changing Speed

When light rays enter a

more optically dense

medium

bull Speed decreases

bull Wavelength decreases

bull Frequency remains

constant

bull Light ray bends towards

the normal

hellipcontinued

When light rays enter a

less optically dense

medium

bull Speed increases

bull Wavelength increases

bull Frequency remains

constant

bull Light ray bends away from

the normal

hellipcontinued

When light rays

enters a medium of

different optical

density along the

normal - it does not

change direction

Links What is the link between angle of incidence and

angle of reflection

What property of the glass block will determine how

much the light is refracted

n = sin i

sin r

Sine of the angle

of incidence

Sine of the angle

of refraction Refractive

Index

16052016 copycgrahamphysicscom 2016

How can you find the index of refraction experimentally

bull This is a common exam questions

bull You need to describe exactly what you do

16052016 copycgrahamphysicscom 2016

Answer Practical questions on experiments mustshellip

You must discuss 1 What you would change (independent variable) what you

would measure (dependent variable) 2 What instruments would you use and how would you use

them How would you use them carefully 3 Plot these results on a graph What does the gradient give 4 What would you repeat and why 5 Mention several precautions you will make so that the

results are as accurate as possible

16052016 copycgrahamphysicscom 2016

Method bull Determining Refractive Index Experiment bull Draw around the glass block bull Mark positions of incident and emerging rays using a pencil

or two pins bull Remove block and draw refracted ray inside the rectangle bull Measure the incident angle i between the incident ray and

the normal bull Measure the refracted angle between the refracted ray r

and the normal bull Measure the same two angles for different angles of

incidence

16052016 copycgrahamphysicscom 2016

The big picture

Have you ever wondered

Can reflection and refraction effects save lives

Diabetic eye disease

Eye cancer 16052016 copycgrahamphysicscom 2016

Changing Speed

When light rays enter a

more optically dense

medium

bull Speed decreases

bull Wavelength decreases

bull Frequency remains

constant

bull Light ray bends towards

the normal

hellipcontinued

When light rays enter a

less optically dense

medium

bull Speed increases

bull Wavelength increases

bull Frequency remains

constant

bull Light ray bends away from

the normal

hellipcontinued

When light rays

enters a medium of

different optical

density along the

normal - it does not

change direction

Links What is the link between angle of incidence and

angle of reflection

What property of the glass block will determine how

much the light is refracted

n = sin i

sin r

Sine of the angle

of incidence

Sine of the angle

of refraction Refractive

Index

16052016 copycgrahamphysicscom 2016

How can you find the index of refraction experimentally

bull This is a common exam questions

bull You need to describe exactly what you do

16052016 copycgrahamphysicscom 2016

Answer Practical questions on experiments mustshellip

You must discuss 1 What you would change (independent variable) what you

would measure (dependent variable) 2 What instruments would you use and how would you use

them How would you use them carefully 3 Plot these results on a graph What does the gradient give 4 What would you repeat and why 5 Mention several precautions you will make so that the

results are as accurate as possible

16052016 copycgrahamphysicscom 2016

Method bull Determining Refractive Index Experiment bull Draw around the glass block bull Mark positions of incident and emerging rays using a pencil

or two pins bull Remove block and draw refracted ray inside the rectangle bull Measure the incident angle i between the incident ray and

the normal bull Measure the refracted angle between the refracted ray r

and the normal bull Measure the same two angles for different angles of

incidence

16052016 copycgrahamphysicscom 2016

Changing Speed

When light rays enter a

more optically dense

medium

bull Speed decreases

bull Wavelength decreases

bull Frequency remains

constant

bull Light ray bends towards

the normal

hellipcontinued

When light rays enter a

less optically dense

medium

bull Speed increases

bull Wavelength increases

bull Frequency remains

constant

bull Light ray bends away from

the normal

hellipcontinued

When light rays

enters a medium of

different optical

density along the

normal - it does not

change direction

Links What is the link between angle of incidence and

angle of reflection

What property of the glass block will determine how

much the light is refracted

n = sin i

sin r

Sine of the angle

of incidence

Sine of the angle

of refraction Refractive

Index

16052016 copycgrahamphysicscom 2016

How can you find the index of refraction experimentally

bull This is a common exam questions

bull You need to describe exactly what you do

16052016 copycgrahamphysicscom 2016

Answer Practical questions on experiments mustshellip

You must discuss 1 What you would change (independent variable) what you

would measure (dependent variable) 2 What instruments would you use and how would you use

them How would you use them carefully 3 Plot these results on a graph What does the gradient give 4 What would you repeat and why 5 Mention several precautions you will make so that the

results are as accurate as possible

16052016 copycgrahamphysicscom 2016

Method bull Determining Refractive Index Experiment bull Draw around the glass block bull Mark positions of incident and emerging rays using a pencil

or two pins bull Remove block and draw refracted ray inside the rectangle bull Measure the incident angle i between the incident ray and

the normal bull Measure the refracted angle between the refracted ray r

and the normal bull Measure the same two angles for different angles of

incidence

16052016 copycgrahamphysicscom 2016

hellipcontinued

When light rays enter a

less optically dense

medium

bull Speed increases

bull Wavelength increases

bull Frequency remains

constant

bull Light ray bends away from

the normal

hellipcontinued

When light rays

enters a medium of

different optical

density along the

normal - it does not

change direction

Links What is the link between angle of incidence and

angle of reflection

What property of the glass block will determine how

much the light is refracted

n = sin i

sin r

Sine of the angle

of incidence

Sine of the angle

of refraction Refractive

Index

16052016 copycgrahamphysicscom 2016

How can you find the index of refraction experimentally

bull This is a common exam questions

bull You need to describe exactly what you do

16052016 copycgrahamphysicscom 2016

Answer Practical questions on experiments mustshellip

You must discuss 1 What you would change (independent variable) what you

would measure (dependent variable) 2 What instruments would you use and how would you use

them How would you use them carefully 3 Plot these results on a graph What does the gradient give 4 What would you repeat and why 5 Mention several precautions you will make so that the

results are as accurate as possible

16052016 copycgrahamphysicscom 2016

Method bull Determining Refractive Index Experiment bull Draw around the glass block bull Mark positions of incident and emerging rays using a pencil

or two pins bull Remove block and draw refracted ray inside the rectangle bull Measure the incident angle i between the incident ray and

the normal bull Measure the refracted angle between the refracted ray r

and the normal bull Measure the same two angles for different angles of

incidence

16052016 copycgrahamphysicscom 2016

hellipcontinued

When light rays

enters a medium of

different optical

density along the

normal - it does not

change direction

Links What is the link between angle of incidence and

angle of reflection

What property of the glass block will determine how

much the light is refracted

n = sin i

sin r

Sine of the angle

of incidence

Sine of the angle

of refraction Refractive

Index

16052016 copycgrahamphysicscom 2016

How can you find the index of refraction experimentally

bull This is a common exam questions

bull You need to describe exactly what you do

16052016 copycgrahamphysicscom 2016

Answer Practical questions on experiments mustshellip

You must discuss 1 What you would change (independent variable) what you

would measure (dependent variable) 2 What instruments would you use and how would you use

them How would you use them carefully 3 Plot these results on a graph What does the gradient give 4 What would you repeat and why 5 Mention several precautions you will make so that the

results are as accurate as possible

16052016 copycgrahamphysicscom 2016

Method bull Determining Refractive Index Experiment bull Draw around the glass block bull Mark positions of incident and emerging rays using a pencil

or two pins bull Remove block and draw refracted ray inside the rectangle bull Measure the incident angle i between the incident ray and

the normal bull Measure the refracted angle between the refracted ray r

and the normal bull Measure the same two angles for different angles of

incidence

16052016 copycgrahamphysicscom 2016

Links What is the link between angle of incidence and

angle of reflection

What property of the glass block will determine how

much the light is refracted

n = sin i

sin r

Sine of the angle

of incidence

Sine of the angle

of refraction Refractive

Index

16052016 copycgrahamphysicscom 2016

How can you find the index of refraction experimentally

bull This is a common exam questions

bull You need to describe exactly what you do

16052016 copycgrahamphysicscom 2016

Answer Practical questions on experiments mustshellip

You must discuss 1 What you would change (independent variable) what you

would measure (dependent variable) 2 What instruments would you use and how would you use

them How would you use them carefully 3 Plot these results on a graph What does the gradient give 4 What would you repeat and why 5 Mention several precautions you will make so that the

results are as accurate as possible

16052016 copycgrahamphysicscom 2016

Method bull Determining Refractive Index Experiment bull Draw around the glass block bull Mark positions of incident and emerging rays using a pencil

or two pins bull Remove block and draw refracted ray inside the rectangle bull Measure the incident angle i between the incident ray and

the normal bull Measure the refracted angle between the refracted ray r

and the normal bull Measure the same two angles for different angles of

incidence

16052016 copycgrahamphysicscom 2016

How can you find the index of refraction experimentally

bull This is a common exam questions

bull You need to describe exactly what you do

16052016 copycgrahamphysicscom 2016

Answer Practical questions on experiments mustshellip

You must discuss 1 What you would change (independent variable) what you

would measure (dependent variable) 2 What instruments would you use and how would you use

them How would you use them carefully 3 Plot these results on a graph What does the gradient give 4 What would you repeat and why 5 Mention several precautions you will make so that the

results are as accurate as possible

16052016 copycgrahamphysicscom 2016

Method bull Determining Refractive Index Experiment bull Draw around the glass block bull Mark positions of incident and emerging rays using a pencil

or two pins bull Remove block and draw refracted ray inside the rectangle bull Measure the incident angle i between the incident ray and

the normal bull Measure the refracted angle between the refracted ray r

and the normal bull Measure the same two angles for different angles of

incidence

16052016 copycgrahamphysicscom 2016

Answer Practical questions on experiments mustshellip

You must discuss 1 What you would change (independent variable) what you

would measure (dependent variable) 2 What instruments would you use and how would you use

them How would you use them carefully 3 Plot these results on a graph What does the gradient give 4 What would you repeat and why 5 Mention several precautions you will make so that the

results are as accurate as possible

16052016 copycgrahamphysicscom 2016

Method bull Determining Refractive Index Experiment bull Draw around the glass block bull Mark positions of incident and emerging rays using a pencil

or two pins bull Remove block and draw refracted ray inside the rectangle bull Measure the incident angle i between the incident ray and

the normal bull Measure the refracted angle between the refracted ray r

and the normal bull Measure the same two angles for different angles of

incidence

16052016 copycgrahamphysicscom 2016

Method bull Determining Refractive Index Experiment bull Draw around the glass block bull Mark positions of incident and emerging rays using a pencil

or two pins bull Remove block and draw refracted ray inside the rectangle bull Measure the incident angle i between the incident ray and

the normal bull Measure the refracted angle between the refracted ray r

and the normal bull Measure the same two angles for different angles of

incidence

16052016 copycgrahamphysicscom 2016

Data bull Draw a graph of sin i vs sin r bull Label the axis and draw line of best fit bull The gradient gives the refractive index Improvements to the method bull Take repetitions and find average bull mark light rays on paper bull use a thinner beam bull fix block firmly in position bull remove anomalies bull use a sharper pencil bull use a more precise protractor Refractive Index of Glass Block using pins

16052016 copycgrahamphysicscom 2016

Exam Question (5 marks)

bull lsquoExplain how a student can use a glass block to find an accurate value for the refractive index of glassrsquo

16052016 copycgrahamphysicscom 2016

Marking scheme bull MP1 mention ray box

bull MP2 Use of protractor

bull MP3 (vary i to) obtain a range of values

bull MP4 Statement of equation n= (sin i) (sin r )

bull MP5 a) plot a graph of sin i against sin r

OR

b) calculate work out find n

bull MP6 a) find gradient of graph

OR

b) calculate average n

bull MP7 sensible precaution or improvement

Including( use ruler for lines use thinner beam single colour disregard anomalous readings use sharp pencil more precise protractor)

16052016 copycgrahamphysicscom 2016

The speed of light

0

30

60

90

120

150

180

210

240

270

300

Va

cuu

m

Wa

ter

Per

spex

Speed of

light

(thousands

kms)

Looking at the chart which do you

think is denser Perspex or water

Perspex must be denser because

light travels slower through Perspex

than water

bull Light travels at 300 000 kms in a vacuum as it enters denser

media the speed of light decreases

As the speed of light varies depending on the medium different materials refract light by different amounts

Refractive index for a medium is calculated by comparing

the speed of light in a vacuum to the speed in that medium

speed of light in vacuum

speed of light in medium

Refractive index is a measure of how much a substance

slows down light The higher its value the slower light

travels in that medium

Refractive index

The refractive index of air is 1 because light travels at

nearly the same speed in air as it does in a vacuum

refractive index =

119899 =119888

119907

16052016 copycgrahamphysicscom 2016

Using refractive index

16052016 copycgrahamphysicscom 2016

Predicting refraction The refractive index of air is 1 and that of diamond is 24 What happens when light goes from diamond into air

Diamond has a higher refractive index than air

This means light speeds up when it leaves the diamond The light will bend away from the normal The angle of incidence is less than or equal to the angle of refraction

higher refractive index

light travels more slowly

16052016 copycgrahamphysicscom 2016

Snellrsquos Law

The general version of

Snells law states that the

ratio of the sines of the

angles of incidence θ1 and

refraction θ2 is equivalent

to the ratio of velocities in

the two media

sinq1

sinq2

=v1

v2

=n2

n1

1198991 sin 1205791 = 1198992 sin 1205792

Snellrsquos Law - Question

Question

A light ray enters a block of

glass as shown Determine

the angle of refraction

Solution 1198991 sin 1205791 = 1198992 sin 1205792 1 sin 35 = 15 sin 1205792

sin 1205792 =sin 35

15

1205792 = sinminus1sin 35

15= 22 50

Refraction in Real Life

Refraction can make fishing with a spear difficult

Key words

bull Refractive index - measure of the bending of a ray of light when passing from one medium into another If i is the angle of incidence of a ray in vacuum and r is the angle of refraction the refractive index n is defined as the ratio of the sine of the angle of incidence to the sine of the angle of refraction

bull Snellrsquos Law 1198991 sin 1205791 = 1198992 sin 1205792

16052016 copycgrahamphysicscom 2016

Marking scheme bull MP1 mention ray box

bull MP2 Use of protractor

bull MP3 (vary i to) obtain a range of values

bull MP4 Statement of equation n= (sin i) (sin r )

bull MP5 a) plot a graph of sin i against sin r

OR

b) calculate work out find n

bull MP6 a) find gradient of graph

OR

b) calculate average n

bull MP7 sensible precaution or improvement

Including( use ruler for lines use thinner beam single colour disregard anomalous readings use sharp pencil more precise protractor)

16052016 copycgrahamphysicscom 2016

The speed of light

0

30

60

90

120

150

180

210

240

270

300

Va

cuu

m

Wa

ter

Per

spex

Speed of

light

(thousands

kms)

Looking at the chart which do you

think is denser Perspex or water

Perspex must be denser because

light travels slower through Perspex

than water

bull Light travels at 300 000 kms in a vacuum as it enters denser

media the speed of light decreases

As the speed of light varies depending on the medium different materials refract light by different amounts

Refractive index for a medium is calculated by comparing

the speed of light in a vacuum to the speed in that medium

speed of light in vacuum

speed of light in medium

Refractive index is a measure of how much a substance

slows down light The higher its value the slower light

travels in that medium

Refractive index

The refractive index of air is 1 because light travels at

nearly the same speed in air as it does in a vacuum

refractive index =

119899 =119888

119907

16052016 copycgrahamphysicscom 2016

Using refractive index

16052016 copycgrahamphysicscom 2016

Predicting refraction The refractive index of air is 1 and that of diamond is 24 What happens when light goes from diamond into air

Diamond has a higher refractive index than air

This means light speeds up when it leaves the diamond The light will bend away from the normal The angle of incidence is less than or equal to the angle of refraction

higher refractive index

light travels more slowly

16052016 copycgrahamphysicscom 2016

Snellrsquos Law

The general version of

Snells law states that the

ratio of the sines of the

angles of incidence θ1 and

refraction θ2 is equivalent

to the ratio of velocities in

the two media

sinq1

sinq2

=v1

v2

=n2

n1

1198991 sin 1205791 = 1198992 sin 1205792

Snellrsquos Law - Question

Question

A light ray enters a block of

glass as shown Determine

the angle of refraction

Solution 1198991 sin 1205791 = 1198992 sin 1205792 1 sin 35 = 15 sin 1205792

sin 1205792 =sin 35

15

1205792 = sinminus1sin 35

15= 22 50

Refraction in Real Life

Refraction can make fishing with a spear difficult

Key words

bull Refractive index - measure of the bending of a ray of light when passing from one medium into another If i is the angle of incidence of a ray in vacuum and r is the angle of refraction the refractive index n is defined as the ratio of the sine of the angle of incidence to the sine of the angle of refraction

bull Snellrsquos Law 1198991 sin 1205791 = 1198992 sin 1205792

16052016 copycgrahamphysicscom 2016

The speed of light

0

30

60

90

120

150

180

210

240

270

300

Va

cuu

m

Wa

ter

Per

spex

Speed of

light

(thousands

kms)

Looking at the chart which do you

think is denser Perspex or water

Perspex must be denser because

light travels slower through Perspex

than water

bull Light travels at 300 000 kms in a vacuum as it enters denser

media the speed of light decreases

As the speed of light varies depending on the medium different materials refract light by different amounts

Refractive index for a medium is calculated by comparing

the speed of light in a vacuum to the speed in that medium

speed of light in vacuum

speed of light in medium

Refractive index is a measure of how much a substance

slows down light The higher its value the slower light

travels in that medium

Refractive index

The refractive index of air is 1 because light travels at

nearly the same speed in air as it does in a vacuum

refractive index =

119899 =119888

119907

16052016 copycgrahamphysicscom 2016

Using refractive index

16052016 copycgrahamphysicscom 2016

Predicting refraction The refractive index of air is 1 and that of diamond is 24 What happens when light goes from diamond into air

Diamond has a higher refractive index than air

This means light speeds up when it leaves the diamond The light will bend away from the normal The angle of incidence is less than or equal to the angle of refraction

higher refractive index

light travels more slowly

16052016 copycgrahamphysicscom 2016

Snellrsquos Law

The general version of

Snells law states that the

ratio of the sines of the

angles of incidence θ1 and

refraction θ2 is equivalent

to the ratio of velocities in

the two media

sinq1

sinq2

=v1

v2

=n2

n1

1198991 sin 1205791 = 1198992 sin 1205792

Snellrsquos Law - Question

Question

A light ray enters a block of

glass as shown Determine

the angle of refraction

Solution 1198991 sin 1205791 = 1198992 sin 1205792 1 sin 35 = 15 sin 1205792

sin 1205792 =sin 35

15

1205792 = sinminus1sin 35

15= 22 50

Refraction in Real Life

Refraction can make fishing with a spear difficult

Key words

bull Refractive index - measure of the bending of a ray of light when passing from one medium into another If i is the angle of incidence of a ray in vacuum and r is the angle of refraction the refractive index n is defined as the ratio of the sine of the angle of incidence to the sine of the angle of refraction

bull Snellrsquos Law 1198991 sin 1205791 = 1198992 sin 1205792

16052016 copycgrahamphysicscom 2016

Refractive index for a medium is calculated by comparing

the speed of light in a vacuum to the speed in that medium

speed of light in vacuum

speed of light in medium

Refractive index is a measure of how much a substance

slows down light The higher its value the slower light

travels in that medium

Refractive index

The refractive index of air is 1 because light travels at

nearly the same speed in air as it does in a vacuum

refractive index =

119899 =119888

119907

16052016 copycgrahamphysicscom 2016

Using refractive index

16052016 copycgrahamphysicscom 2016

Predicting refraction The refractive index of air is 1 and that of diamond is 24 What happens when light goes from diamond into air

Diamond has a higher refractive index than air

This means light speeds up when it leaves the diamond The light will bend away from the normal The angle of incidence is less than or equal to the angle of refraction

higher refractive index

light travels more slowly

16052016 copycgrahamphysicscom 2016

Snellrsquos Law

The general version of

Snells law states that the

ratio of the sines of the

angles of incidence θ1 and

refraction θ2 is equivalent

to the ratio of velocities in

the two media

sinq1

sinq2

=v1

v2

=n2

n1

1198991 sin 1205791 = 1198992 sin 1205792

Snellrsquos Law - Question

Question

A light ray enters a block of

glass as shown Determine

the angle of refraction

Solution 1198991 sin 1205791 = 1198992 sin 1205792 1 sin 35 = 15 sin 1205792

sin 1205792 =sin 35

15

1205792 = sinminus1sin 35

15= 22 50

Refraction in Real Life

Refraction can make fishing with a spear difficult

Key words

bull Refractive index - measure of the bending of a ray of light when passing from one medium into another If i is the angle of incidence of a ray in vacuum and r is the angle of refraction the refractive index n is defined as the ratio of the sine of the angle of incidence to the sine of the angle of refraction

bull Snellrsquos Law 1198991 sin 1205791 = 1198992 sin 1205792

16052016 copycgrahamphysicscom 2016

Using refractive index

16052016 copycgrahamphysicscom 2016

Predicting refraction The refractive index of air is 1 and that of diamond is 24 What happens when light goes from diamond into air

Diamond has a higher refractive index than air

This means light speeds up when it leaves the diamond The light will bend away from the normal The angle of incidence is less than or equal to the angle of refraction

higher refractive index

light travels more slowly

16052016 copycgrahamphysicscom 2016

Snellrsquos Law

The general version of

Snells law states that the

ratio of the sines of the

angles of incidence θ1 and

refraction θ2 is equivalent

to the ratio of velocities in

the two media

sinq1

sinq2

=v1

v2

=n2

n1

1198991 sin 1205791 = 1198992 sin 1205792

Snellrsquos Law - Question

Question

A light ray enters a block of

glass as shown Determine

the angle of refraction

Solution 1198991 sin 1205791 = 1198992 sin 1205792 1 sin 35 = 15 sin 1205792

sin 1205792 =sin 35

15

1205792 = sinminus1sin 35

15= 22 50

Refraction in Real Life

Refraction can make fishing with a spear difficult

Key words

bull Refractive index - measure of the bending of a ray of light when passing from one medium into another If i is the angle of incidence of a ray in vacuum and r is the angle of refraction the refractive index n is defined as the ratio of the sine of the angle of incidence to the sine of the angle of refraction

bull Snellrsquos Law 1198991 sin 1205791 = 1198992 sin 1205792

16052016 copycgrahamphysicscom 2016

Predicting refraction The refractive index of air is 1 and that of diamond is 24 What happens when light goes from diamond into air

Diamond has a higher refractive index than air

This means light speeds up when it leaves the diamond The light will bend away from the normal The angle of incidence is less than or equal to the angle of refraction

higher refractive index

light travels more slowly

16052016 copycgrahamphysicscom 2016

Snellrsquos Law

The general version of

Snells law states that the

ratio of the sines of the

angles of incidence θ1 and

refraction θ2 is equivalent

to the ratio of velocities in

the two media

sinq1

sinq2

=v1

v2

=n2

n1

1198991 sin 1205791 = 1198992 sin 1205792

Snellrsquos Law - Question

Question

A light ray enters a block of

glass as shown Determine

the angle of refraction

Solution 1198991 sin 1205791 = 1198992 sin 1205792 1 sin 35 = 15 sin 1205792

sin 1205792 =sin 35

15

1205792 = sinminus1sin 35

15= 22 50

Refraction in Real Life

Refraction can make fishing with a spear difficult

Key words

bull Refractive index - measure of the bending of a ray of light when passing from one medium into another If i is the angle of incidence of a ray in vacuum and r is the angle of refraction the refractive index n is defined as the ratio of the sine of the angle of incidence to the sine of the angle of refraction

bull Snellrsquos Law 1198991 sin 1205791 = 1198992 sin 1205792

16052016 copycgrahamphysicscom 2016

Snellrsquos Law

The general version of

Snells law states that the

ratio of the sines of the

angles of incidence θ1 and

refraction θ2 is equivalent

to the ratio of velocities in

the two media

sinq1

sinq2

=v1

v2

=n2

n1

1198991 sin 1205791 = 1198992 sin 1205792

Snellrsquos Law - Question

Question

A light ray enters a block of

glass as shown Determine

the angle of refraction

Solution 1198991 sin 1205791 = 1198992 sin 1205792 1 sin 35 = 15 sin 1205792

sin 1205792 =sin 35

15

1205792 = sinminus1sin 35

15= 22 50

Refraction in Real Life

Refraction can make fishing with a spear difficult

Key words

bull Refractive index - measure of the bending of a ray of light when passing from one medium into another If i is the angle of incidence of a ray in vacuum and r is the angle of refraction the refractive index n is defined as the ratio of the sine of the angle of incidence to the sine of the angle of refraction

bull Snellrsquos Law 1198991 sin 1205791 = 1198992 sin 1205792

16052016 copycgrahamphysicscom 2016

Snellrsquos Law - Question

Question

A light ray enters a block of

glass as shown Determine

the angle of refraction

Solution 1198991 sin 1205791 = 1198992 sin 1205792 1 sin 35 = 15 sin 1205792

sin 1205792 =sin 35

15

1205792 = sinminus1sin 35

15= 22 50

Refraction in Real Life

Refraction can make fishing with a spear difficult

Key words

bull Refractive index - measure of the bending of a ray of light when passing from one medium into another If i is the angle of incidence of a ray in vacuum and r is the angle of refraction the refractive index n is defined as the ratio of the sine of the angle of incidence to the sine of the angle of refraction

bull Snellrsquos Law 1198991 sin 1205791 = 1198992 sin 1205792

16052016 copycgrahamphysicscom 2016

Refraction in Real Life

Refraction can make fishing with a spear difficult

Key words

bull Refractive index - measure of the bending of a ray of light when passing from one medium into another If i is the angle of incidence of a ray in vacuum and r is the angle of refraction the refractive index n is defined as the ratio of the sine of the angle of incidence to the sine of the angle of refraction

bull Snellrsquos Law 1198991 sin 1205791 = 1198992 sin 1205792

16052016 copycgrahamphysicscom 2016

Key words

bull Refractive index - measure of the bending of a ray of light when passing from one medium into another If i is the angle of incidence of a ray in vacuum and r is the angle of refraction the refractive index n is defined as the ratio of the sine of the angle of incidence to the sine of the angle of refraction

bull Snellrsquos Law 1198991 sin 1205791 = 1198992 sin 1205792

16052016 copycgrahamphysicscom 2016