Module 4 - Section 2 - Types Of Waves

Question 1

What is a transverse wave ?

Answer 1

A transverse wave is a wave where the direction of the oscillations is perpendicular to the direction of energy transfer

Question 2

What are some examples of transverse waves ?

Answer 2

• Waves on a string
• Ripples on water
• All EM waves
• S-waves

Question 3

Whats the most common type of longitudinal wave ?

Answer 3

Sound waves

Question 4

What are mechanical waves ?

Answer 4

Mechanical waves require particles to transfer energy ( they have to travel through a medium )

Question 5

What is a Longitudinal Wave ?

Answer 5

It is when the direction of oscillation is parallel to the direction of energy transfer

Question 6

What are the 2 ways of drawing transverse waves ?

Answer 6

They can be shown as graphs of DISPLACEMENT against DISTANCE

OR

They can be shown as graphs of DISPLACEMENT against TIME

Question 7

Whats the displacement upwards from the centre line given as ?

Answer 7

+ sign

Question 8

what can be the displacement distance graph used to measure ?

Answer 8

A displacement distance wave profile can be used to show the wavelength of the wave and the amplitude of both types of waves ( transverse and longitudinal )

You measure the wavelength like normal and you measure the amplitude like normal

Question 9

Whats a wave profile ?

Answer 9

A wave profile is a graph showing the displacement of particles in the wave against the distance along the wave

Question 10

What can you measure from displacement time wave profile ?

Answer 10

A graph of displacement against time can easily be used to determine the period T and the amplitude of both types of waves - so you measure the period just like you would measure a normal wavelength but instead of measuring the wavelength you are measuring the period as there is time instead of distance on the x axis

Question 11

Look at the graph with the letter A plotted as a point in the CGP book page 78 ( in blue )
What direction is point A on the wave moving in ?
And then explain how to calculate that

Answer 11

Point A is travelling upwards - all you do is look at the displacement to the left of the the point and you can see that the displacement is much bigger therefore it has to iMovie up to get to that displacement and if the displacement to the left of the point was less then the point A would have the direction of downwards as it would have to move downwards to get to that displacement

Question 12

What does a sound wave consist of ?

Answer 12

It consists of a series of compressions and rarefactions of the medium its travelling through - that’s why sound can’t go through a vacuum as there’s no particles in a vacuum

Question 13

Why is it hard to represent longitudinal waves graphically ?

Answer 13

Because they look like transverse waves

Question 14

How do you plot longitudinal waves on graph ?

Answer 14

Displacement against time graphs - although its hard because they look like transverse waves

Question 15

What is intensity ?

Answer 15

Intensity is a measure of how much energy a wave is carrying

Intensity is the rate of flow of energy per unit area at right to the direction of travel of the wave - its measured in Wm*-2

Question 16

When you talk about brightness for light or loudness for sound what are we really referring to ?

Answer 16

When we are referring to how bright a light is what we really mean is how much energy hits you eyes per second

When we are referring to how loud a sound is we are referring to how much energy hits your ears per second

The measure of this is called intensity

Question 17

Whats the scientific definition of intensity ?

Answer 17

Intensity is the rate of flow of energy per unit area at right angles to the direction of travel of the wave

Question 18

Whats intensity measured in ?

Answer 18

Intensity is measured in Wm*-2

Question 19

Whats the equation for Intensity ?

Answer 19

Intensity = Power / area

Question 20

What is intensity proportional to ?

Answer 20

Intensity is proportional to amplitude squared

And this is because intensity is proportional to the energy carried by the wave - and the energy of a wave depends on the square of the amplitude

Question 21

What properties do the EM waves have in common ?

Answer 21

• All EM waves travel can travel in a vacuum at a speed of 3.00x10*8 ms and at slower speeds in other media
• They are transverse waves consisting of vibrating electric and magnetic fields - these electric and magnetic fields are at right angles to each other and to the direction of travel
• Like all waves, EM waves can be refracted, reflected and diffracted and can undergo interference. They also obey the v = f x landa equation
• Like all progressive waves, EM waves carry energy
• EM waves are transverse so, like all transverse waves, they can be polarised

Question 22

Whats the order of the EM spectrum ? And which one has the smallest frequency and which one has the smallest wavelength ?

Answer 22

Radio waves, microwaves, infrared, visible light, ultraviolet, x-rays and gamma rays

Radio waves have the smallest frequency as they have the biggest wavelength and gamma rays have the smallest wavelength and therefore have the most frequency

Question 23

The longer the wavelength the….

Answer 23

The more obvious the wave characteristics become - long radio waves diffract around hills

Question 24

What is energy directly proportional to ?

Answer 24

The energy that the wave carries is directly proportional to the frequency of the wave - gamma rays have the highest energy and radio waves have the lowest

Question 25

The higher the energy that the wave carries the more …

Answer 25

Dangerous the wave becomes as some waves can even cause ionisation

Question 26

Whats the approximate wavelength (m), how penetrative it is and what are the uses of

Radio waves ?

Answer 26

• Radio waves have a wavelength of 10-1 - 106
• Radio waves are able to pass through matter
• The uses of radio waves are - radio transmissions

Question 27

What are the uses, penetration and approximate wavelength in m of..
Micro waves ?

Answer 27

The approximate length in m is 10-3 - 10-1

Microwaves mostly pass though matter but cause some heating ]

Microwaves are sued for radar, microwave cooking and Tv transmissions

Question 28

What are the uses, penetration and approx wavelength in m for …
Infrared radiation

Answer 28

The approx wavelength in m is — 7x10-7 to 10-3

It’s mostly absorbed by matter, causing it to heat up

Infrareds can be used for heat detectors, night vision cameras, remote controls and optical fibres

Question 29

What is the approx wavelength in m and what’s the uses and penetration ability of visible light ?

Answer 29

The approx wavelength in m for visible light is —> 4x10-7 — 7x10-7

visible light is absorbed by matter which causes some heating

Visible light is used for optical fibres and human sight

Question 30

Whats the approx wavelength of UV and what’s the penetration and uses of UV ?

Answer 30

The approx wavelength of Uv is —> 10-8 — 4x10-7

UV rays are absorbed by matter and there is slight ionisation

The uses of UV light are - sun beds, security markers that show up under UV light

Question 31

What is the approx wavelength for X rays and what are the uses and penetration for X-rays ?

Answer 31

The approx wavelength for X-rays is —> 10-13 — 10-8

X-rays mostly pass through matter but they cause ionisation as they pass

The uses of X-rays are —> to see damage form broken bones and teeth, airports security scanners and to kill cancer cells

Question 32

Whats the approx wavelength for gamma rays and what are the uses and penetration of gamma rays ?

Answer 32

The approx wavelength in m for gamma is —> 10-16 — 10-10

Gamma rays mostly pas though matter but they cause ionisation as they pass

Gamma rays are used for —> the irradiation of food, sterilisation of medical instruments and to kill cancer cells