Waves Chapter 5

Question 1

What are longitudinal waves

Answer 1

Waves which the direction of vibrating of the particles is parallel to along the direction in which the wave travels
Waves that are like a slinky

Question 2

What are transverse waves

Answer 2

Waves in which the direction of vibration is perpendicular to the direction in which wave travels
Goes up and down

Question 3

What is polarisation

Answer 3

Where it involves transverse waves which are in a plane polarised if the vibrations stay in one plane only.

Question 4

Polarisation from one plane to another

Answer 4

Polarised from one plane to another the waves are in polarised

Question 5

What happens if unpolarised light passes through a Polaroid

Answer 5

It transmits light is polarised as the filter only allows through light which vibrates in a certain direction, according to the alignment of its molecules

Question 6

What happens if Unpolarised light passes through two Polaroid filters

Answer 6

The transmitted light intensity changed if one Polaroid is turned relative to the other one.

Question 7

What happens if Unpolarised light passes through two Polaroid filters
Pt2

Answer 7

Crossed and transmitted intensity is a minimum this position shows the polarised light from the first filter cannot pass through the second filter as the alignment of molecules in the second filter is at 90⁰ to the alignment in the first filter.

Question 8

Phase difference

Answer 8

Phase of a vibrating particles at a certain time is the fraction of a cycle it has completed since the start of the cycle.
The phase difference is between two particles vibrating at the same frequency is the fraction of a cycle between the vibrations of the two particles measured either degrees or radians.

Question 9

Wave speed info

Answer 9

Higher the speed and frequency of the wave shorter the wavelength.

Higher the frequency close together the wave peaks are

Question 10

Wave speed equation

Answer 10

Wave speed = c = f x λ

C = distance travelled in one cycle / time taken for one cycle

C = λ÷ 1÷f
= fx λ

Question 11

Parts of a wave

Answer 11

Amplitude - from middle line to the height of ether wave

Wavelength - from one wavelength to another

Trough - from the bottom of the wave to the middle line

Question 12

Key terms

Displacement

Answer 12

Of a vibrating particle is it’s distance and direction from its equilibrium position

Question 13

Key terms

Amplitude

Answer 13

Maximum displacement of a vibrating particle for a transverse wave it is distance from the middle to the peak of the wave.

Question 14

Key terms

Wavelength

Answer 14

Least distance between two adjacent vibrating particles with the same displacement and velocity at the same time

Question 15

Key terms

Cycle

Answer 15

When a vibrating particle is displaced unit is return to its stored.

Question 16

Key terms

Period

Answer 16

Period of a wave is the same time for one complete wave to pass a fixed point

Question 17

Key terms

Frequency

Answer 17

Numb of cycles of wave that pass a point per second

Question 18

What’s a progressive wave

Answer 18

To distinguish them from stationary waves. They combine at fixed points along the rope to form point of no displacement or nodes along the rope. At each node the two sets of waves are always 180⁰ out of phase so they cancel each other out.

Question 19

Antinode

Answer 19

Fixed point in a stationary wave pattern where amplitude is maximum

Question 20

Node

Answer 20

fixed point in a stationary wave pattern where the amplitude is zero

Question 21

Stationary wave

Answer 21

Stationary wave is formed when two progressive waves pass through each other
This can be achieved on a string tension by fixing both ends and making the middle part vibrate so progressive wave and travel towards each end reflects at the end and then pass through each other

Question 22

Superposition

Answer 22

When two waves meet they pass through each other at a certain point where they meet, they combine for an instant before they move apart
The total displace at a point is equal to the sum of the individual displacement at that point

Question 23

What happens when two crest meet

Answer 23

Make a super test created by two waves reinforce each other

Question 24

What happens when two trough meet

Answer 24

Make a supertrough

Question 25

What happens when a crest and a trough meet

Answer 25

If the both have the same amplitude the resultant displacement is zero the waves Cancel each other out if they are not the same amplitude the resultant is called a minimum

Question 26

Frequency

Answer 26

F= c/λ

Question 27

Wave speed

Answer 27

fλ = c

Question 28

Wavelength

Answer 28

λ=c/f

Question 29

The refractive index

Answer 29

N= sin i / sin r

Question 30

Wavefront

Answer 30

Lien that connects all the point on a wave that are in phase

Question 31

Refraction

Answer 31

Change of direction due to a change of speed caused by a change in density

Question 32

What occurs to refraction

Answer 32

Retraction occurs because the speed of the light waves is ditterent in each substance. The amount of refraction that takes place depends on the speed of the waves in each substance.

Question 33

Snells law calculation 1

Answer 33

``` Cst = sin(r) x XY Ct= sin(i) x XY Cst/sin(r) = XY = ct/sin(i) ``` Rearrange Ct/cst = sin(i)/sin(r) C/cs = sin(i) / sin(r) = N

Question 34

Snells law calculation 2

Answer 34

N1 x sin(i) = N2 x sin(r)

Question 35

Refractor equation

Answer 35

N1 x sin(i) ÷ N2 = Angle of refraction

Question 36

Incidence equation

Answer 36

Sin(r) x N2 / N1

Question 37

Critical angle

Answer 37

Sin0₁ = N2 / N1

Question 38

What is critical angle

Answer 38

The angle of incidence where the refracted ray travels along the boundary between the two medium Angle of i = critical i = c

Question 39

Total internal reflection occurs when

Answer 39

1. i > c angle of incidence is larger than the critical angle 2. Light travels from more dense to less dense medium Sin0c = N2/N1

Question 40

Optical fibres

Answer 40

Optical fibres are used in medical endoscopes to see inside the body, and in communications to carry light signals.

Question 41

What does optical fibres do

Answer 41

They allow pulses of light that enter at one end from a transmitter to reach a receiver at the other end

Question 42

Total internal reflection takes place when

Answer 42

The cor cladding boundary at any point where two fibres are in direct contact light would cross from one fibre to the other if there were no cladding.

Question 43

Medical endoscope

Answer 43

medical endoscope contains two bundles of fibres. The endoscope is inserted into a body cavity, which is then illuminated using light sent through one of the fibre bundles. A lens over the end of the other fibre bundle is used to form an image of the body cavity on the end of the fibre bundle. The light that forms this image travels along the fibres to the other end of the fibre bundle where the image can be observed. This fibre bundle needs to be a coherent bundle, which means that the Fibre ends at each end are in the same relative positions.

Question 44

Interference

Answer 44

Occurs when two coherent progress waves travelling in the same direction Similar amplitude Same frequency constant phase difference Two waves diffract and super pose to form a regular interference pattern

Question 45

Constructive interference

Answer 45

Occurs when the position of the path is difference a whole number of wavelength nλ

Question 46

Destructive interference

Answer 46

Occurs when the path difference = a whole number plus half a wavelength n + 1/2 λ

Question 47

Fringe separation

Answer 47

W= λ x D / s ``` D = distance λ = wavelength S = split spacing W = fringe separation ```

Question 48

Double slit equation

Answer 48

S1 x P - S2 x P = m x λ Two slits S1,S2 P point on the screen M =1,2,3,4 etc …

Question 49

Wavelength and colour 650nm 350nm

Answer 49

1. Red light | 2. Violet

Question 50

Single slit diffraction width

Answer 50

W = λ / a x 2D ``` A = single slit D= split screen distance ```

Question 51

Through a single slit

Answer 51

The central fringe is twice as wide as each of the outer fringes Each of the outer fringes is the same width

Question 52

Intensity

Answer 52

Peak intensity of each fringe decreases with distance from the centre The outer fringes are much less intense than the central fringe

Question 53

Diffraction wavelength

Answer 53

Greater the wavelength the wider the fringe | Width of the central fringe is proportional to the wavelength

Question 54

Diffraction grating

Answer 54

diffraction grating consists of a plate with many closely spaced parallel slits ruled on it. When a parallel beam of monochromatic light is directed normally at a diffraction grating, light is transmitted by the grating in certain directions only. This is because: the light passing through each slit is diffracted

Question 55

Diffraction grating equation

Answer 55

D x sin0 = n x λ

Question 56

Stationary wave equation

Answer 56

F= 1/ 2x L √ t/u ``` F= frequency L = length T= tension U = mass per unit length ```

Question 57

Describe when some light is refracted and some light is reflected at a boundary

Answer 57

Internal reflection

Question 58

Modal dispersion

Answer 58

The lengthening of a light pulse as it travels along an optical fibre due to rays that repeatedly undergo total internal reflection having to travel along distance than rays that undergo fewer total internal reflections