Types Of Waves & Polarisation

Question 1

In [……..] waves, vibration is at right angles to the direction of travel.

Answer 1

Transverse

Question 2

What type of waves are electromagnetic waves?

Answer 2

Transverse waves

Question 3

Displacement upwards is given a [……..] sign

Answer 3

+ (positive)

Question 4

What two graphs can waves be drawn on?

Answer 4

Displacement - distance

Displacement - time

Question 5

In […….] waves the vibrations are along the direction of travel.

Answer 5

Longitudinal

Question 6

What is the most common example or longitudinal waves?

Answer 6

Sound

Question 7

What does a sound wave consist of?

Answer 7

Compressions and rarefactions

Question 8

How do you measure one wavelength on a sound wave?

Answer 8

From 1 compression to another

Question 9

Compressions and rarefactions create pressure variations - which one creates higher pressure?

Answer 9

Compressions and the molecules are closer together.

Question 10

Compressions and rarefactions create pressure variations - which on creates lower pressures?

Answer 10

Rarefactions as the molecules are further apart.

Question 11

What is Reflection?

Answer 11

When the wave is bounced back when it hits a boundary

Question 12

What is refraction?

Answer 12

The wave changes direction as it enters a different medium.

Question 13

What is Intensity?

Answer 13

Is the rate of flow of energy per unit area at right angles to the direction of travel of the wave.

Question 14

What is the Intensity equation?

Answer 14

Intensity = Power / Area

I = P/A

Question 15

What is intensity proportional to?

Answer 15

Amplitude squared

Question 16

What do properties do Electromagnetic Waves have in common?

Answer 16

• All EM waves travel in a vacuum at a speed 3 x 10*8 ms-1
• They are transverse waves (consisting of vibrating electric and magnetic fields)
• Can be retracted, reflected and diffracted and undergo interference
• Obey v = f λ
• EM waves carry energy
• They are transverse so can be polarised

Question 17

When light is reflected it is […….][……]

Answer 17

Partially polarised

Question 18

How do we know that light is partially polarised when it is reflected from a surface?

Answer 18

If you view the reflected Ray through a polarised filter the intensity of light leaving the filter changes with the orientation of the filter.

Question 19

Television and radio signals are […..]

Answer 19

Polarised

Question 20

How are TV signals polarised?

Answer 20

Rods on the aerials polarise the waves through the orientation of these rods on the broadcasting aerial. If the rods on both are not aligned then the signal is weak.

Question 21

How are Radio Waves polarised?

Answer 21

You are moving the alignment of the rods with a radio as the rods go in and out of alignment.

Question 22

Why do polarising filters not work on micro waves?

Answer 22

Because their wavelength is too long.

Question 23

What is used to polarise micro waves?

Answer 23

A metal grille

Question 24

What equipment do you need to investigate the polarisation of microwaves?

Answer 24

Microwave transmitter
Microwave receiver
Link these to a Voltmeter