Waves

Question 1

What is the order of the EM Spectrum from Shortest Wavelength, Highest Energy?

Answer 1

Gamma Rays, X-Rays, Ultraviolet Rays, Visible Light, Infra-red, Microwaves, Radio Waves

Question 2

What is the equation for The Law of Malus?

Answer 2

Light intensity passing through filter (I) = Light intensity entering filter (I0) x cos^2(Angle between E-field of light and axis of filter(ø))

I = I0 cos^2(ø)

Question 3

When Sunlight is reflected off of the ocean, what is the polarisation of the reflected sunlight?

Answer 3

Horizontal

Question 4

What orientation must the polarising filters in sunglasses be set to (given that they are eliminating reflection from horizontal surfaces)?

Answer 4

Vertically Orientated

Question 5

What is the equation for Wavespeed regarding Wavelength and Time Period?

Answer 5

c = λ / T

Question 6

In the equation nλ = d sinθ, what does d represent?

Answer 6

The distance between slits

Question 7

What is Fringe Separation?

Answer 7

The distance between adjacent maxima

Question 8

The sound quality of a portable radio is improved by adjusting the orientation of the aerial. Why is this?

Answer 8

The radio waves from the transmitter are polarised

Question 9

Which one of these waves cannot be polarised? : Radio, Ultraviolet, Microwave, Ultrasound

Answer 9

Ultrasound

Question 10

What band of the EM Spectrum would a wavelength of 200nm belong to?

Answer 10

Ultraviolet

Question 11

What is displacement?

Answer 11

The distance and direction of a particle from the equilibrium position

Question 12

Define amplitude

Answer 12

Maximum displacement of a vibrating particle

Question 13

What is the wavelength?

Answer 13

The shortest distance between two particles in phase

Question 14

Define frequency

Answer 14

Number of wave cycles occurring each second

Question 15

Define wave speed

Answer 15

Distance travelled by a wave each second

Question 16

Define phase difference

Answer 16

The amount by which one wave lags behind another wave, measured in degrees or radians

Question 17

Define path difference

Answer 17

The difference in the lengths of two waves, measured in metres

Question 18

What are progressive waves?

Answer 18

Waves whose oscillations travel and transfer energy

Question 19

What is a transverse wave?

Answer 19

A wave whose oscillations are perpendicular to the direction of travel

Question 20

Are electromagnetic waves transverse or longitudinal?

Answer 20

Transverse

Question 21

What is a longitudinal wave?

Answer 21

A wave whose oscillations are parallel to the direction of travel

Question 22

Are sound waves transverse or longitudinal?

Answer 22

Longitudinal

Question 23

What does it mean if a wave is polarised?

Answer 23

All the waves are oscillating in the same plane

Question 24

Only ____ waves can be polarised

Answer 24

Transverse

Question 25

How is polarisation applicable in regards to glare and cameras?

Answer 25

Is used in polaroid sunglasses sunglasses to reduce glare and in cameras to enhance the image

Question 26

How is polarisation applied in regards to TV and radio signals?

Answer 26

Tv and radio signals are polarised by the direction of the rods on the transmitting aerial

Question 27

How can you ensure that you receive a TV or radio signal well?

Answer 27

By ensuring the receiving aerial and the waves are in the same plane

Question 28

What is superposition?

Answer 28

The point where waves meet

Question 29

What is the total displacement at the point of superposition equal to?

Answer 29

The sum of the individual displacements

Question 30

When does constructive interference occur?

Answer 30

When waves are in phase

Question 31

When does destructive interference occur?

Answer 31

When waves are anti-phase

Question 32

What is created when two peaks/troughs constructively interfere?

Answer 32

A double peak/trough

Question 33

What is created when a peak meets a trough?

Answer 33

They destructively interfere, cancelling each other out to create a minimum point

Question 34

What is a stationary wave?

Answer 34

A wave that stores energy instead of transferring it

Question 35

What is the equation for the fundamental frequency of a wave on a string?

Answer 35

f = 1/2l × sqrt(T/μ)

Question 36

What does raising the tension or shortening the length of the string do to its fundamental frequency?

Answer 36

Increases it

Question 37

In Young's Double Slit Experiment, when illuminated, what did the two double slits act as?

Answer 37

Coherent wave sources

Question 38

What does it mean if a wave source is coherent?

Answer 38

The waves have the same frequency and a constant phase difference

Question 39

In Young's Double Slit Experiment, why is an interference pattern created?

Answer 39

The lights diffracts at the slits and they superpose - a combination of cosntrictive and destructive interference

Question 40

What is the double slit formula, W = λD/s , in words?

Answer 40

Fringe spacing = (wavelength × distance from the screen) /distance between slits

Question 41

How did Young's Double Slit Experiment provide evidence for the wave nature of EM radiation?

Answer 41

Diffraction and interference are purely wave properties

Question 42

What is diffraction?

Answer 42

The spreading out of waves when they pass through a gap or over an edge

Question 43

What does the amount of diffraction depend on?

Answer 43

The gap width and the wavelength of the wave

Question 44

In regards to diffraction, what happens if the gap is a lot bigger than the wavelength?

Answer 44

The diffraction is unnoticeable

Question 45

In regards to diffraction, what happens if the gap is a bit wider than the wavelength?

Answer 45

Diffraction is noticeable

Question 46

In regards to diffraction, what happens if the gap is the same size as the wavelength?

Answer 46

The diffraction is most noticeable

Question 47

In regards to diffraction, what happens if the gap is smaller than the wavelength?

Answer 47

Most of the waves are reflected

Question 48

What is intensity a measure of?

Answer 48

Power delivered per unit area

Question 49

What effect will increasing the Slit width have on a diffraction pattern?

Answer 49

It will create an intense but narrow central maximum

Question 50

What effect will decreasing the Slit width have on a diffraction pattern?

Answer 50

It will create a wider and less intense central maximum

Question 51

What is refraction?

Answer 51

When a wave changes speed when it crosses into a new medium

Question 52

If a wave passes into a medium that is more optically dense, what will happen?

Answer 52

The wave will slow down and bend towards the normal

Question 53

If a wave passes into a medium that is less optically dense, what will happen?

Answer 53

The wave will speed up and bend away from the normal

Question 54

What does a material's refractive index refer to?

Answer 54

How optically dense the medium is

Question 55

What is the absolute refractive index?

Answer 55

How much a medium slows down light, as a ratio

Question 56

What is the equation for absolute refractive index?

Answer 56

n = c / c¹

Question 57

What can we use to predict the angle of refraction for a given angle of incidence?

Answer 57

Snell's Law

Question 58

What is Snell's Law?

Answer 58

n¹sin(θ¹) = n²sin(θ²)

Question 59

In regards to refraction, what is the critical angle?

Answer 59

The angle for which the refracted just passes along the boundary line and beyond which all of the wave will be deflected

Question 60

What is the angle of refraction at the critical angle?

Answer 60

90°

Question 61

In regards to refraction, what happens if the angle of incidence is greater than the critical angle?

Answer 61

The ray is reflected back inside

Question 62

What are the two conditions for Total Internal Reclection to occur?

Answer 62

● Light must travel from a more optically dense to a less optically dense medium. ● The angle of incidence of the light ray must exceed the critical angle.

Question 63

Give three examples of uses of Total Internal Reflection for transferring signals

Answer 63

● High-speed Internet cables ● Medical imaging as endoscopes ● Engineering inspections to view hard to reach areas

Question 64

What are the two main parts of step-index optical fibres?

Answer 64

● A core made of a high-refractive index material. ● Cladding made of a low-refractive index material.

Question 65

In an optical fibre, what are three purposes of the cladding?

Answer 65

● Provides tensile strength so it doesn't break when twisted. ● Prevents information transferring between different cores. ● Prevents core being damaged

Question 66

Why must optical fibres be protected from scratches?

Answer 66

Water may get in or the angle at which the signal hits the boundary may change

Question 67

What happens if water gets into an optical fibre?

Answer 67

● Refractive index increases ● TIR cannot occur ● Signal exits core

Question 68

What might a scratch do to an optical fibre?

Answer 68

Alter the angle at which the signal interacts with the core's boundary such that the angle is lowered below the critical angle, preventing TIR and causing signal loss outside of the fibre

Question 69

In regards to waves, what is absorption?

Answer 69

When energy is lost as a signal travels through an optical fibre

Question 70

In regards to waves, what does absorption cause?

Answer 70

A loss of amplitude but no effect on the frequency

Question 71

In regards to waves, how can the effects of absorption be reduced?

Answer 71

By using an optical fibre repeater to boost the signal at periodic points

Question 72

In an optical fibre, what is modal dispersion?

Answer 72

When multiple beams enter a fibre at different angles, causing them to undergo TIR a different number of times and making them reach the end at different times, creating pulse broadening.

Question 73

In an optical fibre, what is material dispersion?

Answer 73

A consequence of a signal containing several different wavelengths so they travel at different speeds, causing pulse broadening