waves ~~~~~~~~~~~~

Question 1

what are progressive waves?

Answer 1

an oscillation that travels through matter (or in some cases vacums) that transfer energy from one place to another without transferring matter

Question 2

what is a longitudinal wave?

Answer 2

direction of energy transfer is parallel to oscillations

Question 3

what are transverse waves?

Answer 3

direction of energy transfer is perpendicular to oscillation

Question 4

what is the wave equation?

Answer 4

Question 5

what can be measured from distance displacement wave profiles?

Answer 5

• wavelength
• amplitude

snapshot of the wave

Question 6

what would a displacement distance wave profile look like for a transverse wave?

Answer 6

Question 7

what would a displacemnet distnace wave profile look like for a longitudinal wave?

how would you identify compressions and rarefactions?

Answer 7

centre of compression/ rarefaction has 0 displacement
* centre of compression: positive –> negative
* centre of rarefaction: negative–> positive

Question 8

How do you convert between radian and degrees?

Answer 8

360°= 2π radian
180°= π radian

Question 9

what is “phase difference”?

Answer 9

difference in displacement of particles along a eave, or in 2 different waves

measured in difference

Question 10

what is meant by the term “in phase”?

Answer 10

phase difference of 0 or a multiple of 2π radians (360°)

Question 11

what is meant by the term “antiphase”?

Answer 11

a phase difference of π radians (180°)

Question 12

what can be measured from a distplacment time wave profile?

Answer 12

• amplitude
• time period (frequency)

Question 13

what is reflection?

Answer 13

when a wave changes direction at a boundary between two media, remaining in the original medium
* wavelength, frequnecy do not change

Question 14

what is a wavefront?

Answer 14

Lines of constant phase

Question 15

what is refracation?

Answer 15

when a wave changes speed as it changes direction at the boundary of two media
* frequnecy the same
* wavespeed and wavelength change

will always be partial reflection

Question 16

what happens when waves moves to denser mediums

Answer 16

• normal waves: speed up, move away from the normal
• EM waves slow down, move towards the normal

Question 17

what is diffraction?

Answer 17

the spreading out of a wave front as it passes through a gap
* hyeogens principle: when a wave is disturbed each point where there is a disturbance becomes a source for a spherical wave

maximim difraction when gap is same size as incident wavelength

Question 18

define displacement

Answer 18

• distance and direction moved from the equilibrium position
• [s]
• units SI (m)

vector so negative or positive

Question 19

define Amplitude

Answer 19

• the maximum displacement from the equilibrium position
• [A]
• units SI (m)

vectors positive or negative

Question 20

define Wavelength

Answer 20

• the distance between two adjacent vibrating particles/points with same velocity, at same displacement
• [λ]
• units SI (m)

Question 21

define Time period

Answer 21

• the time taken for one oscillation/ wave to move one whole wavelength past a given point
• [T]
• units SI (s)

Question 22

define frequency

Answer 22

• the number of wavelengths passing a given point per second
• [f]
• units SI (Hz)

Question 23

define Wave Speed

Answer 23

• the distance travelled by the wave per unit of time
• [v]/[c]
• SI unit ms-1

Question 24

describe distance displacment graphs

Answer 24

• shows the displacement of several points on a wave at a particular time
• “snapshot”
• wavelength, amplitude

several particles

Question 25

describe displacemnt time graph

Answer 25

* shows the displacment of a point at several times * "video of a single particle" time period, frequnecy,amplitude

Question 26

Clock and sin wave

Answer 26

Question 27

Clock and sin wave

Answer 27

Question 28

Are these waves inphase, out of phase or Antiphase

Answer 28

In phase as everything is perfectly aligned

Question 29

How would you calculate if waves are in phase or anti phase according to wavelength ?

Answer 29

Question 30

How would you calculate if 2 waves are in phase or anti phase according to phase difference?

Answer 30

Question 31

Define electro magnetic waves

Answer 31

Waves that travel by oscillations of the electromagnetic field. Always transverse waves

Question 32

What is the electro magnetic spectrum and the corresponding wavelengths ?

Answer 32

Question 33

What is the order of visible light

Answer 33

ROYGBIV Richard of York gave battle in vain Red, orange, yellow, green, blue, indigo, violet

Question 34

What is polarisation ?

Answer 34

Can only be done to transverse waves, applying a filter to light

Question 35

What is a plane polarised light?

Answer 35

A transverse wave where oscillations are limited to only one plane

Question 36

What happens when two polarised filters are perfectly aligned ?

Answer 36

Question 37

What happens when two Polaroid filters are at 90° to each other?

Answer 37

Question 38

Describe the use of Polaroid sun glasses

Answer 38

1. light is horizontally polarsied (from water/metal surfaces) 2. sunglasses have vertically alligned filtesr blobking all this polarised light 3. this reduces the bright glare

Question 39

What is Snells Law?

Answer 39

Question 40

What is refractive index?

Answer 40

How much it slows down

Question 41

What happens to the angle of incidence / refraction when moving from one medium to another?

Answer 41

Question 42

Define total internal reflection

Answer 42

The reflection of all light back into the original medium when hitting a boundary between two media; * the original medium will have a higher refractive index (n1>n2) * the incidence angle at the boundary must be greater than the critical angle

Question 43

Define critical angle

Answer 43

The angle of incidence at the boundary between 2 media, that will produce an angle of refraction of 90°

Question 44

What is the critical angle ?

Answer 44

Question 45

What is the formula for the critical angle?

Answer 45

Question 46

What happens in fibre optic cables ?

Answer 46

Total internal reflection

Question 47

Does frequency change when wave speed changed ?

Answer 47

Question 48

Does refractive index vary with frequency?

Answer 48

Question 49

What are the two types of waves and how do they specifically transfer energy?

Answer 49

Waves transfer energy via oscillations

Question 50

what is the phase of a point/particle?

Answer 50

the fraction of a complet cycle/ wave that a point is at

Question 51

Answer 51

Question 52

What happens to the wavefronts in diffraction?

Answer 52

Question 53

Describe refraction in terms of wavefronts

Answer 53

Part of wavefronts change speed first causing the change in direction, when at an angle to the normal

Question 54

What are the refraction rules for EM waves and mechanical waves?

Answer 54

Question 55

what are the rules for diffraction?

Answer 55

* wave speed, wavelength: do not change * the longer the wavelength the more the wave spreads out * the smaler the gap relative to the wavelength, the greater the diffraction

Question 56

what is polarisation?

Answer 56

* a property of transverse waves * defines the plane of oscillation of the wave

Question 57

what is the plane of polarisation of an EM wave?

Answer 57

the plane in which the **electric field** vibrates

Question 58

how is light (EM waves) polarised with filters?

Answer 58

* plane of allignment of the filter is the plane in which E-field oscillations pass through * transmitted light is polarised in the same plane | allows all components of waves in that certain direction not just E fiel

Question 59

what is unpolarised light?

Answer 59

* **wave trains **(a group of waves of equal or similar wavelengths travelling in the same direction)

Question 60

What is Malus Law?

Answer 60

Question 61

how is light polarised by reflection?

Answer 61

* on metal surfaces and water * polarised in the horizontal plane

Question 62

How do polarising filters work?

Answer 62

Question 63

Answer 63

* unpolarised light from lamp * p1 polarises the light in the vertical plane * p2 polarises light int the horizontal plane * but there is no component of vertically plane polarised light that lays in the horizontal direction

Question 64