Polarisation

Question 1

What is meant by a plane-polarised wave

Answer 1

when unpolarised light is polarised, the electric field oscillations occur in only one plane. This is the plane of polarisation

Question 2

The effect on light of polarisers and analysers

Answer 2

if two polarisers with the same orientation transmit light in the same plane.
if one is rotated 90° then light is blocked where they overlap.

Question 3

when a ray of unpolarised light is incident on the surface of an insulator at Brewster’s angle the reflected ray becomes

Answer 3

plane-polarised

Question 4

Derivation of n=taniₚ

Answer 4

n=siniₚ/sinr
but iₚ +r = 90° 
so n = siniₚ/sin(90-iₚ)
thus n=siniₚ/cosiₚ
so n =taniₚ

Question 5

n=taniₚ

Answer 5

n = refractive index
iₚ = Brewster's angle (°)

Question 6

how would you arrange two polarising filters so that the two images do not interfere

Answer 6

they should be arranged 90° to each other

Question 7

How does an arrangement which contains two polarising filters, one for each eye, enable a different image to be seen by each eye

Answer 7

One filter will let through the vertically polarised light and will block the horizontal

and

The other filter will let through horizontal light and block the vertical

Question 8

Light from a lamp

Answer 8

is unpolarised light

Question 9

Light from a screen such as a tv, or cinema screen

Answer 9

is polarised light

Question 10

When a filter is rotated 90° when looking through at a lamp what is the change in brightness

Answer 10

there is no change as the lamp is unpolarised light

Question 11

If you look at a screen through one filter and rotate it 90° there will be no brightness change why?

Answer 11

As there is only one filter the image from one plane will decrease and the image from the other will increase, thus the brightness stays the same

Question 12

what would happen when two polarising filters are rotated 180°

Answer 12

it would be at its minimum brightness at 90°

it would be at its maximum brightness at 180°

Question 13

if a polariser is removed from two filters and it is rotated 180° what would happen

Answer 13

the brightness remains constant

Question 14

how do polarising sunglasses reduce the glare compared to non-polarising sunglasses

Answer 14

The polarising sunglasses will act as an analyser and block the glare.

Question 15

to find the angle of refraction when you have brewster’s angle you must

Answer 15

refraction angle = 90 - brewster’s angle