Chapter 11 Waves 1

Question 1

What are primary and secondary waves?

Answer 1

They are both forms of progressive waves

Question 2

What is an S-wave?

Answer 2

A secondary wave that is transverse

Question 3

What is a P-wave?

Answer 3

A primary wave that is longitudinal

Question 4

What is a progressive wave?

Answer 4

It is a wave that moves through matter or a vacuum and It transfers energy without transferring matter.

Question 5

What is an equilibrium position in terms of waves?

Answer 5

It is the position that particles are in when there is no wave passing through it. Any deviation from this position is a deviation from the equilibrium

Question 6

What is a restoring force?

Answer 6

This is the force that a particle experiences when it is restored back to its original position

Question 7

What is a transverse wave?

Answer 7

It is a wave that oscillates perpendicular to the direction of travel of the wave.

Question 8

What are some examples of transverse waves?(4)

Answer 8

Waves on the surface of water
Any electromagnetic wave
Waves on a stretched string
Swaves produced by earthquakes

Question 9

What is a peak and what is a trough?

Answer 9

These are both the maximum displacement of a particle from equilibrium. Peak is the positive displacement and a trough is the negative displacement

Question 10

What is a longitudinal wave?

Answer 10

It is a wave that oscillates parallel to the direction that the waves travel

Question 11

What are some examples of longitudinal waves?(2)

Answer 11

Sound

pwaves from earthquakes

Question 12

What is a compression and a rarefaction?

Answer 12

A compression is an area of high pressure and a rarefaction is an area of low pressure

Question 13

What is displacement?

Answer 13

It is the distance that a particle is from equilibirum

Question 14

What is amplitude?

Answer 14

It is the maximum displacement from equilibrium

Question 15

What is wavelength?

Answer 15

This is the minimum distance between two identical points on a wave

Question 16

What is the period of oscillation?

Answer 16

This is the time it takes for one oscillation

Question 17

What is the frequency?

Answer 17

It is the number of wavelengths passing a point in a second, also the number of oscillations per second

Question 18

What is wave speed?

Answer 18

It is the distance travelled by a wave per unit of time

Question 19

What is the wave equation?

Answer 19

V = Fλ

Question 20

What is the equation to find frequency from time period?

Answer 20

f = 1/t
f = frequency
t = timeperiod

Question 21

What is phase difference?

Answer 21

it is Difference between the displacements of particles on a wave

Question 22

What does in phase mean?

Answer 22

This is when particles are oscillating perfectly in step with each other. The reach there maximum displacements at the same time

Question 23

What is the opposite of in phase and what does it mean?

Answer 23

Antiphase is when the particles are completely (180*) out of step and when one particle reaches it maximum positive displacement the other (equivalent) particle reaches its most negative displacement

Question 24

What is a displacement-distance graph show?

Answer 24

It is a graph of the displacement per distance the wave has traveled. And it can also be interpreted as a snapshot of the wave. The wavelength can be calculated by measuring the distance between any two points on the graph

Question 25

What is a displacement-time graph?

Answer 25

It shows the displacement of a particle on a wave as time varies. The frequency can be worked out by counting the number of waves per interval of time (second)

Question 26

What is a reflection?

Answer 26

It is when a wave changes direction at a boundary between two different media whilst still remaining in the original medium

Question 27

What is the law of reflection?

Answer 27

The angle of incidence is equal to the angle of reflection

Question 28

How can light be represented?

Answer 28

It can be represented as a ray ( a straight line) or a wave front (perpendicular lines to the direction that the light moves)

Question 29

What is refraction?

Answer 29

This is when light changes the medium it flows through and due to the change in speed it changes direction

Question 30

What happens if the speed of the wave slows down when changing medium?

Answer 30

Refract towards the normal

Question 31

What happens if the speed of the wave increases when changing medium?

Answer 31

It refracts away from the normal

Question 32

What happens if a) light or b) sound enters a denser medium?

Answer 32

a) When light enters a denser medium it slows down | b) when sound enters a denser medium it speeds up

Question 33

What happens when light enters water from air?

Answer 33

It bends towards the normal and the wavelength gets smaller

Question 34

What is diffraction and what is the property unique to?

Answer 34

Diffraction is unique to waves and is when it spreads out as it passes through a gap

Question 35

What is polarisation? and plane polarisation?

Answer 35

This is when particles oscillate in a single direction. along a single plane

Question 36

What does unpolarised light look like?

Answer 36

It is light that oscillates in multiple directions.

Question 37

What does the amount of diffraction rely on?

Answer 37

It relies on the size of the gap that it passes through and the wavelength

Question 38

What does partial polarisation? and when does it happen?

Answer 38

This is when light oscillates in more than one plane but it not fully unpolarised. its sort of half way between This happens when light reflects off a surface like a lake

Question 39

What is intensity and what is its equation and units?

Answer 39

It is the radiant power passing through a surface per unit of area. I = P / A Units: Wm^-2

Question 40

What is the equation for intensity from a sphere?

Answer 40

I = P / 4πr^2

Question 41

What happens to the intensity if the distance from a source doubles?what is the general equation

Answer 41

The intensity is 1/4 | I ∝ 1/r^2

Question 42

How is amplitude and intensity related?

Answer 42

Intensity ∝ (amplitude)^2

Question 43

What is special about electromagnetic waves vs other waves?

Answer 43

It does not need a medium to pass through

Question 44

What is the order of the electromagnetic spectrum from large to small wavelength?

Answer 44

``` Radio wave Microwave Infrared Visible Ultraviolet Xray Gamma Ray ```

Question 45

What is the wave equation for electromagnetic waves?

Answer 45

c = fλ

Question 46

What is the speed of light? and symbol?

Answer 46

c = 3x10^8

Question 47

What is a polarising filter and how does it work?

Answer 47

It is a filter that polarises light. It acts like a gate and so only the light that is oscillating with the direction of the rails is allowed through. Light that oscillated differently is simply cut out

Question 48

What is a use for polarising filters and explain how this is usefull?

Answer 48

It is used for ariels where the wave is polarised to reduce interference between different transmitters.

Question 49

What is a refractive index?

Answer 49

This is a measure of how light bends when changing between mediums. Each medium is given a factor

Question 50

What is the equation for the refractive index?

Answer 50

``` n = c / v n = refractive index factor c = speed of light in vacuum v = speed of light in the medium ```

Question 51

What medium has a refractive index of 1?

Answer 51

A vacuum

Question 52

What is the refraction law equation?

Answer 52

n1Sinθ1 = n2Sinθ2 n1 is the refractive index of medium 1 and θ1 is the angle of incidence against the normal n2 is the refractive index of medium 2 and θ2 is the angle of incidence against the normal

Question 53

What medium has the highest refractive index?

Answer 53

Diamond with an index of 2.42

Question 54

What is total internal reflection?

Answer 54

This is when light leaving a medium is at such an angle that when it strikes the boundary and reflects instead of refracts

Question 55

What are the two conditions of total internal reflection?

Answer 55

The light must be travelling from a medium of high refractive index towards one of low refractive index The angle at which the light strikes the boundary must be above the critical angle

Question 56

What is the critical angle?

Answer 56

This is the smallest angle that produces a total internal reflection. It is dependent on the medium involved

Question 57

What is the equation for the critical angle?

Answer 57

Sinθ = 1 / n | n is the refractive index of the medium that the light is travelling through

Question 58

How can the refractive index be calculated?

Answer 58

A ray box is used to put light into a semicircular box and then the angle of incident is change with the ray box until it totally internally reflects at an angle of 90* to the normal. The angle between the incident light from the ray box and the normal is calculated. Then the equation Sin θ = 1 / n is used