Chapter 6

Question 1

What does the principle of superposition state?

Answer 1

That when 2 or more waves overlap (superpose), the resultant displacement at a given instant and position is equal to the sum of the individual displacements at that instant and position.

Question 2

A wave transfers energy away from [ ]

Answer 2

It’s source

Question 3

A progressive (moving) wave carries [ ] and usually information from one place to another without transferring any [ ]

Answer 3

Energy

Material

Question 4

How can you tell that EM waves carry energy?

Answer 4

They heat things

Question 5

How can you tell that X-rays and Gamma rays carry energy?

Answer 5

They knock electrons out of their orbits, causing ionisation

Question 6

How can you tell that sound waves carry energy?

Answer 6

They cause things to vibrate

Question 7

How can you tell that water waves carry energy?

Answer 7

Wave power can be used to generate electricity

Question 8

Since waves carry energy, the source of the wave [ ]

Answer 8

Loses energy

Question 9

Define Displacement (X, m)

Answer 9

How far a point on the wave has moved from its undisturbed position

Question 10

Define Amplitude (a, m)

Answer 10

Maximum displacement

Question 11

Define Wavelength (λ, m)

Answer 11

The length of one whole wave

Question 12

Define Period (T, s)

Answer 12

The time taken for a whole vibration

Question 13

Define Frequency (f, Hz)

Answer 13

The number of vibrations per second passing a given point

Question 14

Define phase difference

Answer 14

The amount by which one wave lags behind another wave (degrees or radians)

Question 15

What is intensity?

Answer 15

The rate of flow of energy per unit area perpendicular to the direction of travel of the wave

Question 16

Equation for intensity

Answer 16

Intensity (I, Wm⁻²) = Power (P, W) / Area (A, M²)

Question 17

When does superposition happen?

Answer 17

When 2 or more waves pass through each other

Question 18

Superposition: What happens at the instant the waves cross?

Answer 18

The displacements from each wave combine

Question 19

The principle of superposition:

Answer 19

When 2 or more waves cross, the resultant displacement = the vector sum of the individual displacements

Question 20

Interference can be [ ] or [ ]

Answer 20

Constructive or Destructive

Question 21

What is total destructive interference?

Answer 21

When a peak and a trough are of equal size and they completely cancel each other out

Question 22

When is destructive interference not total?

Answer 22

When the waves are not the same size

Question 23

What are the arrows called, that represent wave superposition?

Answer 23

Phasors

Question 24

In [ ] means in step

Answer 24

Phase

Question 25

2 points on a wave are in phase if they are both at the [ ] in the [ ].

Answer 25

same point | wave cycle

Question 26

360° = ? Radians

Answer 26

2π Radians

Question 27

Describe the waves that are in phase

Answer 27

Points that have a phase difference of 0 or a multiple of 360° are in phase. Their phasors point in the same direction.

Question 28

Describe the waves that are in anti-phase

Answer 28

Points with a phase difference of odd-number multiples of 180°. Their phasors point in opposite directions.

Question 29

To get interference patterns the 2 sources must be [

Answer 29

Coherent.

Question 30

Define coherent

Answer 30

2 waves are coherent if they have the same wavelength and frequency and a fixed phase difference between them.

Question 31

Define path difference:

Answer 31

The amount by which the path travelled by one wave is linger than the path travelled by the other wave

Question 32

Describe the situation where you will get constructive interference from 2 waves

Answer 32

At any point an equal distance from both sources (coherant and in phas) or where the path difference os a whole number of wavelengths Path difference = nλ

Question 33

Describe the situation where you will get total destructive interference from 2 waves

Answer 33

At any point where the path difference is an odd number of half wavelengths Path difference = (2n+1)λ / 2 = (n + 1/2) λ

Question 34

What happens when a wave passes through a gap roughly the same width as its wavelength?

Answer 34

The waves spread out.

Question 35

What does diffraction alter?

Answer 35

ONLY how far the wave spreads out.

Question 36

What does the zeroth, first and second order represent?

Answer 36

The maximums produced at a path difference of zero, one and two wavelengths.

Question 37

What equation can we use to determine the wavelength of light passing through two slits? What can we also use this for?

Answer 37

dsin θ = n λ. Diffraction gratings.

Question 38

What difference does having a diffraction grating vs two slits make?

Answer 38

Brighter image, sharper fringe pattern and can also spread white light out into its component colours because each wavelength of light will produce a maximum at a different angle.

Question 39

Line separation=

Answer 39

1/number of lines per metre

Question 40

Snells Law-

Answer 40

n=sini/sinr=C1stmedium/C2ndMedium