Unit 2.4 - The Nature of Waves

Question 1

Progressive waves

Answer 1

A pattern of disturbances travelling through a medium and carrying energy with it

Question 2

What does a progressive wave involve?

Answer 2

The particles of the medium oscillating about their equilibrium position

Question 3

Oscillating

Answer 3

Vibrating

Question 4

Equilibrium position of a particle

Answer 4

Mid point of oscillations

Question 5

Definition of a wave

Answer 5

Transfer energy without any transfer of matter

Question 6

When is energy transferred with a wave?

Answer 6

As the wave propagates

Question 7

What happens as a wave propagates?

Answer 7

Energy is transferred from 1 point in the medium to another

Question 8

What are the types of progressive waves?

Answer 8

Transverse or longitudinal

Question 9

What types of waves are transverse and longitudinal waves?

Answer 9

Progressive

Question 10

Transverse waves

Answer 10

Oscillations (of the particles) are at right angles to the direction of travel of the wave

Question 11

Example of transverse waves

Answer 11

Electromagnetic waves

Question 12

Draw a diagram to present a transverse wave

Answer 12

(See notes)

Question 13

Draw a diagram to represent a longitudinal wave

Answer 13

(See notes)

Question 14

In which direction are the oscillations in transverse waves?

Answer 14

Perpendicular to the direction of propagation of the wave

Question 15

Longitudinal waves

Answer 15

Oscillations (of the particles) are parallel to the direction of travel of the wave

Question 16

In which direction are the oscillations in a longitudinal wave?

Answer 16

In the same direction as the propagation of the wave

Question 17

Example of longitudinal waves

Answer 17

Sound waves

Question 18

Draw a graph and label the wavelength, amplitude and 1 complete wave cycle of the wave on it

Answer 18

(See notes)

Question 19

Displacement (m) (in terms of waves)

Answer 19

The instance of a particle form its equilibrium position at any instant

Question 20

Amplitude

Answer 20

The maximum value of displacement

Question 21

Amplitude symbol

Answer 21

A

Question 22

Which feature of a wave is the same at all point?

Answer 22

Amplitude

Question 23

Wavelength

Answer 23

The minimum distance between 2 points of a wave which are oscillating in phase

Question 24

Wavelength symbol

Answer 24

(Lambda)

Question 25

Frequency symbol

Answer 25

f

Question 26

Frequency

Answer 26

The number of cycles of a wave that pass a given point in 1 second, which is the same as the number of oscillations performed per second by any particle in the medium through which it is travelling

Question 27

Unit of frequency

Answer 27

Hertz (Hz)

Question 28

What is 1Hz equivalent to?

Answer 28

1 wave per second/1 cycle per second

Question 29

Period symbol

Answer 29

T

Question 30

Period

Answer 30

The time taken for one complete cycle

Question 31

Period equation

Answer 31

T = 1/f

Question 32

What’s f in T = 1/f?

Answer 32

Frequency

Question 33

What’s T in T = 1/f?

Answer 33

Period

Question 34

Speed of a wave

Answer 34

The distance that the wave profile moves per unit time

Question 35

Waves in phase

Answer 35

2 waves that have the same frequency and are at the same point in their cycles at the same time

Question 36

When are wave sources in phase?

Answer 36

If as they leave the sources, the waves have the same frequency and are at the same point in their cycles at the same time

Question 37

Antiphase

Answer 37

2 points are said to be in antiphase if they are at opposite points in their cycle at the same time

Question 38

If a wave is neither in phase or antiphase, what is it in?

Answer 38

“Out-of-phase”

Question 39

Draw a diagram to explain what a radian is

Answer 39

(See notes)

Question 40

Radian

Answer 40

An arc equivalent to the length of the radius The natural unit for angle measurement

Question 41

What can we talk about between ANY 2 points on a wave?

Answer 41

Phase difference

Question 42

What is a complete cycle of a wave equivalent to in terms of radians and in degrees?

Answer 42

2πrad 360 degrees

Question 43

How much are 2 points oscillating in phase in a wave separated by (radians and degrees)?

Answer 43

2πrad 360 degrees

Question 44

How much are two points oscillating in antiphase out of phase in radians and degrees?

Answer 44

πrad 180 degrees

Question 45

How out of phase in radians and degrees are two points in a wave that are a quarter of a wave apart?

Answer 45

π/2 90 degrees

Question 46

How do we calculate the speed of a wave?

Answer 46

c = f(lambda)

Question 47

Where does the c = f(lambda) come from?

Answer 47

Speed = distance/time Specific case where the distance moved by the wave is exactly equal to 1 wavelength Therefore, the time elapsed must equal the period Speed = distance/time ——> speed = (lambda)/period Inputting into T = 1/f, using c as the symbol for speed… c = f(lambda)

Question 48

What can the equation c = f(lambda) be used for?

Answer 48

Any type of wave

Question 49

How would we set up plane waves in water?

Answer 49

Ripple tank

Question 50

Wavefronts

Answer 50

A surface over which the phase of the wave is constant

Question 51

Draw a diagram of plane waves as a series of wavefronts

Answer 51

(See notes)

Question 52

3 features of wavefronts

Answer 52

Have all points oscillating in phase The distance between successive wavefronts is equal to the wavelength of the waves Are at right angles to the direction of travel (propagation) of the waves

Question 53

Draw and label a graph of displacement against position

Answer 53

(See notes)

Question 54

What are the two types of wave graphs we can get?

Answer 54

Displacement against position Displacement against time

Question 55

What type of wave can be represented using a displacement position or displacement time graph?

Answer 55

Transverse

Question 56

What actually IS the displacement against position graph of a wave?

Answer 56

A snapshot (a picture of a wave at a particular time) of a transverse wave

Question 57

What can we easily determine from a displacement position graph?

Answer 57

Wavelength

Question 58

Draw and label a displacement against time graph for a wave

Answer 58

(See notes)

Question 59

What does a displacement against time graph for a wave show?

Answer 59

Displacement of any one particle (or point on the wave) against time

Question 60

What can we easily determine from a displacement against time graph?

Answer 60

Amplitude and period

Question 61

What can be calculated from a displacement time graph and how?

Answer 61

Frequency = 1/period Speed = wavelength/period or frequency x wavelength

Question 62

On what type of graph can frequency and speed of a wave be easily calculated?

Answer 62

Displacement against time

Question 63

Polarised wave

Answer 63

A transverse wave in which particle oscillations occur in only one of the directions or planes at right angles to the direction of wave propagation

Question 64

Draw a diagram to represent a polarised wave

Answer 64

(See notes)

Question 65

Draw a diagram to represent an unpolarised wave

Answer 65

(See notes)

Question 66

What type of waves is it not possible to polarise?

Answer 66

Longitudinal

Question 67

Give examples of things than emit unpolarised light

Answer 67

The sun Domestic light bulbs

Question 68

Unpolarised light

Answer 68

Oscillations take place in many directions or planes at once

Question 69

What does a Polaroid sheet/polarising filter do?

Answer 69

Only allows oscillations in 1 direction to pass through

Question 70

What can we use to only allow oscillations in 1 direction to pass through?

Answer 70

Polaroid sheet/polarising filter

Question 71

What happens to all other oscillations when unpolarised waves are passed through a polarising filter?

Answer 71

Absorbed

Question 72

Draw a diagram to represent what polarising filters do

Answer 72

(See notes)

Question 73

What happens when a second polarising sheet is rotated when light is passing through it?

Answer 73

The intensity of light through it varies

Question 74

How do we ensure maximum brightness with Polaroid sheets?

Answer 74

Line them up parallel

Question 75

What happens to the brightness through a Polaroid sheet when 2 are lined up parallel?

Answer 75

Maximum brightness

Question 76

What happens to the brightness through a second Polaroid sheet if they’re lined up perpendicular to each other?

Answer 76

Zero brightness (darkness)

Question 77

How would we get zero brightness (darkness) through a second Polaroid filter?

Answer 77

Line it up perpendicular to the other one

Question 78

definition of a progressive wave

Answer 78

a pattern of disturbances travelling through a medium and carrying energy with it involves the particles of the medium oscillating in their equililbrium positions

Question 79

definition of a progressive wave

Answer 79

a pattern of disturbances travelling through a medium and carrying energy with it involves the particles of the medium oscillating in their equililbrium positions

Question 80

Do waves with longer or shorter wavelengths bend the most?

Answer 80

Longer

Question 81

What’s it important to make reference to when discussing progressive waves?

Answer 81

That it travels from one point in the medium to another

Question 82

What happens in terms of phase with an increased distance from the source with progressive waves?

Answer 82

Phase lag steadily increases with distance from the source

Question 83

Describe the energy in an unpolarised wave

Answer 83

All directions have the same energy The energy in any component is 50% of the total

Question 84

How do we work out the wavelength if we’re given the distance between, for example, 4 wavefronts?

Answer 84

Distance ————— 3 (Not 4 - draw it out and see that there’s 3 wavelengths)

Question 85

What happens to the frequency and wavelength of waves as they travel from deep to shallow water and the propagation speed is less? Why?

Answer 85

Frequency status the same - the same number of waves pass any point (they haven’t been spontaneously created or destroyed) Smaller wavelength (c = f x wavelength)