Unit 2: Waves

Question 1

What are progressive waves?

Answer 1

Progressive waves transfer energy without transferring matter.

Question 2

What are transverse waves?

Answer 2

Transverse waves are waves which the direction of wave movement is perpendicular to the oscillations.

Water waves are an example

Question 3

What are longitudinal waves?

Answer 3

Transverse waves are waves which the direction of wave movement is parallel to the oscillations.

Sound waves are an example

Question 4

What is the amplitude?

Answer 4

Maximum displacement from equilibrium

Question 5

What is polarisation?

Answer 5

Reducing of transverse waves oscillating in a particular direction as the other directions are absorbed by a polaroid.

Question 6

What is a wavelength?

Answer 6

The minimum distance between 2 oscillating points in phase with each other

Question 7

What is frequency?

Answer 7

The number of cycles per second

Question 8

What is the period

Answer 8

The time taken for 1 complete cycle

Question 9

How are frequency and period linked?

Answer 9

Period = 1/frequency

Question 10

How can wave speed be calculated?

Answer 10

C=fλ

Question 11

What is diffraction and how does it work?

Answer 11

Diffraction is the spreading of a wave when it passes through a slit or objects.
If the slit is larger than the wave length little diffraction occurs, however if the slit is the same size or smaller than the slit then the wave spread will be 180°

Question 12

What is a diffraction grating? And what happens when a light source travels through them

Answer 12

Diffraction gratings are an opaque material that have many narrow equally spaced slots.
When a light source travels through a diffraction grating a pattern of bright fringes appears.

Question 13

What is superposition and when does it occur?

Answer 13

Superposition occurs when 2 waves meet and its the interference between these 2 waves.

Question 14

What is constructive interference?

Answer 14

Constructive interference is when 2 waves that are in phase meet, they will form an amplitude which is the sum of each individual amplitude.

Question 15

What is destructive interference?

Answer 15

Destructive interference is when 2 waves which are out of phase meet and they will cause an amplitude of 0.

Question 16

What are stationary waves?

Answer 16

Stationary waves are when 2 waves of equal frequency and amplitude, travelling in opposite directions interfere with each other causing them to superimpose.

Question 17

What is the formula for Young’s Double Slit?

Answer 17

Wavelength =
Split separation x Fringe separation / Distance from split to screen

Question 18

What is the formula for diffraction grating?

Answer 18

Order x Wavelength =
Split separation / sinθ

Question 19

What is refraction?

Answer 19

Refraction is the change of speed of a wave within a new medium.

Question 20

What is the refractive index?

Answer 20

The ratio to tell how you much slower a wave will trave when entering a medium

Its the
original speed/Final speed
n=c/v

Question 21

What does a high refractive index tell you?

Answer 21

A high refractive index tells you that light travels slower and that light will bend more towards the normal.

Question 22

What is Snell’s law?

Answer 22

n1sin(i) = n2sin(r)

Question 23

What is the critical angle?

Answer 23

The critical angle is the angle of incidence which causes the light to refract along the boundary

Question 24

What is the equation for critical angle?

Answer 24

Sinθ = n2/n1

Question 25

What is total internal reflection?

Answer 25

When θ1 is greater than the critical angle then no light is refracted all light is reflected within the first medium

Question 26

What are the conditions for Total Internal Reflection?

Answer 26

1) the light must be in the medium with a greater reflective index
2) angle of incidence must be greater than the critical angle

Question 27

What is Total Internal Reflection used in and how?

Answer 27

It’s used within optic fibres to transfer data by using light and total internal reflection

Question 28

How do optic fibres work?

Answer 28

Light travels through a medium which has a high refractive index, this medium is then covered by a cladding which has a lesser refractive index.

Question 29

What are the different types of fibres?

Answer 29

Multimode fibres and monomode fibres

Question 30

What are multimode fibres?

Answer 30

Multimode fibres are fibres which have multiple paths of light travelling within them each taking their own path.

Question 31

What are monomode fibres?

Answer 31

Monomode fibres are fibres with only 1 path of light travelling through them

Question 32

What is Multimode dispersion?

Answer 32

Multimode dispersion is the spreading of the individual paths of light in Multimode fibres as they overlap each other

Question 33

How is Multimode dispersion countered?

Answer 33

Multimode fibres are limited to short distances to prevent the dispersion

Question 34

How are constructive and destructive interferences shown?

Answer 34

Constructive:
nλ path difference or 0°/360° in phase

Destructive:
(n+1/2)λ path difference or 180° out of phase