Polarisation

Question 1

What are the different types of Polarisation

Answer 1

Linear, Circular, Elliptical and unpolarised

Question 2

What is Irradiance proportional to?

Answer 2

To the average square of the electric field.

Question 3

What are Polarisation Phenomena about?

Answer 3

The direction and Amplitude of the Electric field.

Question 4

What does Polarisation describe?

Answer 4

The behaviour of the electric field associated with light

Question 5

What kind of wave is light in isotrophic materials

Answer 5

A transverse wave

Question 6

What happens to the direction of the electric field during linear polarisation?

Answer 6

It remains constant

Question 7

How does a polaroid produce linearly polarised light?

Answer 7

By transmitting the electric vector along the axis of the polaroid and absorbing the perpendicular electric vector.

Question 8

When does a polaroid placed in front of polarised light transmit the most?

Answer 8

When it is rotated parallel to the direction of polarisation

Question 9

Can light be partially Polarised

Answer 9

Yes

Question 10

What are the conditions for linear polarisation?

Answer 10

The direction of the electric field vector remains constant.

Question 11

What are the conditions for circular polarisation?

Answer 11

The x and y amplitudes of E are equal and there is a phase difference of pi/2 between them.

Question 12

What are the conditions for elliptical polarisation?

Answer 12

The amplitudes of the electric vector E don’t have to be the same and there doesn’t have to be a specific phase difference between them.

Question 13

What is the most general case of polarisation and why?

Answer 13

Elliptical polarisation because the amplitudes of don’t have to equal and neither does the phase.

Question 14

What is unpolarised light?

Answer 14

Consists of light where the electric field varies at random between successive measurements at one point.

Question 15

What is optical activity?

Answer 15

The ability of a material to rotate the direction of linear polarisation as the light travels through.

Question 16

What are the different types of optically active materials?

Answer 16

D-Rotatory and L-Rotatory

Question 17

What direction do D-rotatory materials rotate the polarisation? Give an example of something that is D-rotatory?

Answer 17

Clockwise and Natural sugars

Question 18

What direction do L-rotatory materials rotate the polarisation? Give an example of something that is L-rotatory?

Answer 18

Anti-Clockwise and Chiral amino acids.

Question 19

What can circular polarisers be used for?

Answer 19

To enhance the contrast of LED displays. Light from the display passes through the polariser. Background light is transmitted through the polariser but reflects off the display screen causing it to change handedness. This then means that the background light won’t pass back through the polariser and will be absorbed.

Question 20

What happens in an optically active material?

Answer 20

Light travels through as two circularly polarised rays at slightly different speeds. As there phase difference varies so there direction of linear polarisation also varies.

Question 21

What kind of molecules is optical activity caused by and what structure do they have?

Answer 21

Chiral molecules with a helical twist.

Question 22

What are the components of the prism spectrometer?

Answer 22

Prism, Slit, Collimator, Telescope