G491 Ocr B Advancing Physics Flash Cards

Front 1

Frequency

Back 1

Number of complete oscillations per second

Front 2

Time Period

Back 2

Time taken for one complete oscillation

Front 3

Converging Lens

Back 3

Adds curvature to wavefronts, making light from a point converge to a (focal) point

Front 4

Focal length

Back 4

Distance from the centre of the lens to the focal point

Front 5

Magnification

Back 5

Image Size

___________

Object Size

Front 6

Pixel

Back 6

A pixel is allocated a binary digit

Front 7

Noise Reduction

Back 7

Replaced by taking the median of itself and 8 surrounding pixel values

Front 8

Edge Detection (Laplace Rule)

Back 8

Subtract average of pixel values Above, below, left and right

Front 9

Smoothing (Blurring)

Back 9

Replacing pixel value with mean of itself and 8 surrounding pixels

Front 10

Bit

Back 10

Smallest unit of digital information represented as a 0 or 1

Front 11

Byte

Back 11

8 bit code, which can code for 256 alternatives

Front 12

Resolution

Back 12

Smallest Detail that can be distinguished

Front 13

Resolution (in an image)

Back 13

Linear measurement

______________________

Number of Pixels

Front 14

How can the resolution of an image be increased?

Back 14

Increase the number of pixels on CCD

Use a Lens to enlarge image

Front 15

Potential Difference

Back 15

J C-1

Front 16

Current

Back 16

C s-1

Front 17

Charge

Back 17

A s

Front 18

Resistance

Back 18

V A-1

Front 19

Conductance

Back 19

A V-1

Front 20

Electromotive Force

Back 20

Energy a source can produce for every coulomb of charge flowing round a circuit

Front 21

"Suggest why some p.d. was lost"

Back 21

Amount of Energy dissipated per unit charge inside the source due to its internal resistance

Front 22

Power

Back 22

J s-1

Front 23

Ohms Law

Back 23

Where Voltage is directly proportional to Current

Front 24

Ohmic Conductor

Back 24

Obeys Ohms Law

Front 25

Non-Ohmic Conductor

Back 25

Doesn't obey Ohms Law

Resistance increases as Current increases

Due to heat increasing scattering of atoms

Front 26

Potential Divider

Back 26

Two Resistors in series

Share source voltage into ratio of resistors

Total voltage across resistors = source voltage

Front 27

Sensitivity

Back 27

Change in Output

___________________

Change in Input

Front 28

Response Time

Back 28

Time taken for sensor to give a reading following a change in its input

Front 29

"State a use for Photocells"

Back 29

Generate electricity

Light sensor

Front 30

"State a use for Thermistors"

Back 30

Temperature Gauge

Front 31

"State a use for Strain Gauges"

Back 31

Weighing Scales

Force Meter

Front 32

Sampling Frequency

Back 32

2 x Max Frequency

Front 33

"State a problem if sampling rate / bits used is too low"

Back 33

Forms low Frequency signals

Known as "Aliases"

Front 34

Bit Rate =

Back 34

Bits per Sample x Samples per second

Front 35

Bandwidth =

Back 35

= Highest Frequency - Lowest Frequency

= Bit rate

= 1 / T

(Where T is the time taken to transmit one bit of data in seconds)

Front 36

Noise

Back 36

Random fluctuations in pixel / frequency values which degrade the quality

Front 37

"State what is meant by 'Polarisation'"

Back 37

Can only happen in Transverse waves

Oscillations perpendicular to direction of travel

Unpolarised waves oscillate in all planes

Polarised waves only oscillate in one plane

Vertically polarised waves do not propagate through horizontal polarising filters

Front 38

"State what happens in a Semiconductor when a voltage is applied through it"

Back 38

Differ from both Insulators and Metallic conductors

Small proportion of atoms are ionised, releasing more free electrons

More free electrons means better conductor

Front 39

"How can semiconductors be varied in the manufacturing process?"

Back 39

Doping with an element which forms ions easier / harder releasing more / fewer free electrons

Front 40

Conductor

Back 40

High density of charge carriers

Front 41

Insulator

Back 41

Low density of charge carriers

Front 42

Dense

Back 42

Large mass per unit volume

Front 43

Stiff

Back 43

Difficult to stretch / extend

Indicated by Youngs Modulus

Front 44

Hard

Back 44

Difficult to scratch / indent

Front 45

Brittle

Back 45

Breaks easily

No plastic region

Stress concentrated at crack tip

Stress cannot be relieved by slip

Cracks propagate

Front 46

Tough

Back 46

Resistant to propagation of cracks

Ability to absorb energy

Amount of energy needed to form new surface area

Front 47

Elastic

Back 47

Retains it shape after removal of force

In metals, bonds stretch and atoms return back to their original position

In polymers, long chain of monomers unfold and atoms rotate about their bonds

Obeys Hookes Law

Front 48

Plastic

Back 48

Doesn't retain its shape after removal of force

In metals, planes of atoms dislocate and slip past each other

Front 49

Ductile

Back 49

Ability to be drawn into a wire

In metals, planes of atoms dislocate and slip past each other

Front 50

Malleable

Back 50

Ability to be hammered into shape

Front 51

Breaking Stress

Back 51

Amount of force needed to break a material per metre squared

Front 52

Strong

Back 52

Requires a large breaking stress

Front 53

Crystalline

Back 53

Regular arrangement of atoms in a lattice

Front 54

Polycrystalline

Back 54

Atoms in each grain are arranged regularly in rows within a lattice, with different orientations

Front 55

Amorphous

Back 55

Random arrangement of atoms

No regular structure

Front 56

Metals

Back 56

Crystalline / Polycrystalline

Strong metallic bonding

Sea of delocalised electrons

Non directional bonds

Planes of atoms can Dislocate

Cracks are blunted and Stress can be relieved by Slip

Good conductors due to many free electrons

Front 57

Ceramics

Back 57

Amorphous

Strong Ionic / Covalent Bonding

Directional bonds

Planes of atoms cannot dislocate

Stress cannot be relieved by slip

Stress concentrates in cracks and propagates

Poor conductors in solid state, Good conductors when molten due to mobility of ions

Front 58

Polymers

Back 58

Amorphous / Crystalline

A long chain made up of lots of monomers

Normally made up of carbon atoms

Tangled together

Unfold when extended

Bonds form between monomers which hold them in place relative to each other

Front 59

Composites

Back 59

Combination of two different materials to obtain desired properties from each material

Front 60

"Explain why tensile strength is given as stress measured in Nm-2 rather than as a force measured in N"

Back 60

Strength is a property of a material

Breaking stress takes cross sectional area into account

Front 61

"Suggest why a filament lamp requires more power than an LED for the same frequency of light"

Back 61

Hot filament produces large amount of a infrared

Other colours from visible spectrum need filtering out

Front 62

"State where the energy of electrons goes when passing through an LED"

Back 62

Into creating and emitting photons of light

Front 63

"Cable is stored tightly wound on a reel, suggest why the current should be low"

Back 63

Cooling of cable will be reduced

Power dissipated will raise temperature which could become a hazard

Front 64

"State advantages of digital signals"

Back 64

Less noise / Can be easily removed

Can be reproduced

Can be processed by a computer

Front 65

"State disadvantages of digital signals"

Back 65

Samples reduces frequency range

Introduces low frequency aliases

Loss of resolution

Front 66

"Explain what is meant by the term 'digital samples'"

Back 66

Samples of the signal taken at discrete intervals and quantised on a digital scale composed of a sequence of binary digits

Front 67

"Explain signals become weaker the further they travel from the hub"

Back 67

Signal decreases in amplitude as the wave spreads

Radio noise present in environment

Noise may degrade signal information