PAG 06.3 - Experiments with Polarisation

Question 1

What is polarisation?

Answer 1

Polarisation is the process of preventing all oscillations except those in a single plane.

Question 2

What types of waves can be polarised?

Answer 2

All transverse waves can be polarised. This includes all the waves in the EM spectrum.

Question 3

Why can sound not be polarised?

Answer 3

Longitudinal waves cannot be polarised since their oscillations are parallel to the direction of energy transfer. Sound is a form of longitudinal wave

Question 4

What is observed when light is shone through two polarising filters whose planes are perpendicular to each other?

Answer 4

The first filter blocks all oscillations except those in one plane. This plane is perpendicular to the polarising plane of the second filter, and so cannot pass through it. This means no light is visible through the two filters.

Question 5

How can microwaves be polarised?

Answer 5

Microwaves can be polarised using a metal grid.

Question 6

Describe the nature of waves emitted from a microwave transmitter.

Answer 6

A microwave transmitter will emit polarised waves, with a wavelength of the order of a few centimetres (~3cm).

Question 7

How can microwaves be detected?

Answer 7

Microwaves can be detected using a microwave receiver. This can then be connected to an analogue or digital meter, or to a sound outputter.

Question 8

How will the sound output of the microwave receiver change as the microwave intensity increases

Answer 8

As the intensity of the microwaves increases, the amplitude of the sound will increase. This will result in a louder sound.

Question 9

What safety precautions should be taken when working with microwaves?

Answer 9

You must ensure that the microwave intensity does not exceed the maximum safe level. Microwaves with too high a frequency or intensity can cause burning.

Question 10

Suggest an application for a polarising filter.

Answer 10

Polarising sunglasses use lenses that polarise the light. This helps to reduce the glare from road surfaces when driving.

Question 11

What safety precautions should be taken when using a lamp?

Answer 11

The bulb and surrounding areas may become very hot. Allow to cool after use, avoid touching the bulb and metal areas, and switch it off when not in use.