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Physics. Flashcards

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AP® Physics flashcards Physics 101 flashcards
1
Q

Neutron: Relative Mass? Electrical Charge?

A

Relative Mass: 1 Electrical Charge: 0

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2
Q

Proton: Relative Mass? Electrical Charge?

A

Relative Mass: 1 Electrical Charge: +1 (Positive)

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3
Q

Electron: Relative Mass? Electrical Charge?

A

Relative Mass: 1/1850 Electrical Charge: -1 (Negative)

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4
Q

What is an Element?

A

A pure substance made up of atoms with the same number of protons

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5
Q

What is a mixture?

A

A mixture of two or more different elements.

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6
Q

What is found in the nucleus?

A

Protons and Neutrons

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7
Q

What is a compound?

A

A pure substance made up from more than one element which have been joined together by a chemical reaction.

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8
Q

What is the atomic number?

A

Number of protons found in the nucleus.

Also known as the proton number

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9
Q

What is the mass number?

A

The number of protons and neutrons found in the nucleus.

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10
Q

8 Which is the atomic number and which is the mass number?
O
16
Oxygen

A

8 - Atomic Number
O
16 - Atomic mass
Oxygen

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11
Q

What is a molecule?

A

A pure substance which results when two or more atoms of a single element share electrons.

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12
Q

What is an Isotope?

A

Atoms of the same element with a different number of neutrons but the same number of protons.

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13
Q

What is Ionization?

A

The process of when an atom loses or gains electrons

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14
Q

What is a Cation?

A

A positively charged ion.

Typically a metal

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15
Q

What is an Anion?

A

A Negatively charged ion.

Typically non-metals

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16
Q

Electron Shells: Letter code? Maximum Electrons?

A

1 (K) - Max 2 Electrons
2 (L) - Max 8
3 (M) - Max 18
4 (N) - Max 32

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17
Q

What is valency?

A

The amount of electrons needed to fill the outer shell.

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18
Q

Atoms with a single outer electron or a single missing electron are…..

A

Highly Reactive

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19
Q

Atoms with only a few electrons in the outer shell are good…..

A

Electrical conductors

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20
Q

Atoms with 8 or close to 8 electrons in its outer shell are….

A

Poor electrical conductors but good insulators.

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21
Q

Atoms with 4 electrons on the outer shell are….

A

Semi-conductors

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22
Q

Valance Binding: Valance 1 - 6 and there names?

A 
1 - Monovalent 
2 - Divalent
3 - Trivalent
4 - Tetravalent
5 - Pentavalent
6 - Hexavalent
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23
Q

What is cohesion?

A

The intermolecular force between liquid particle types.

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24
Q

What is adhesion?

A

The intermolecular force between dissimilar atoms.

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25
Q

Cohesion and adhesion are ……….., Atomic bonding is ………

A

Cohesion and adhesion are temporary, Atomic bonding is permanent

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26
Q

What is covalent bonding?

A

Sharing electrons to form molecules.

Usually non-metallic elements

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27
Q

What is ionic bonding?

A

One atom transferring electrons to another atom.

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28
Q

Ionic bonding: The atom loosing the electron becomes a positive or negative ion?

A

The atom loosing the electron becomes a positive ion.

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29
Q

Ionic bonding: The atom gaining the electron becomes a positive or negative ion?

A

The atom gaining the electron becomes a negative ion.

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30
Q

Can ionic bond conduct electicity when in a solid form?

A

No, ionic bonds cannot conduct as a solid but when dissolved the solution then becomes conductive.

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31
Q

Properties of ionic bonds

A 
Strong structures ( Brittle)
High melting points 
High Boiling points
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32
Q

1 slug = ? Kg

A

14.59kg

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33
Q

What is a vector?

A

A quantity that has both size and direction

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34
Q

1 Pound (lb) = ? Newtons

A

4.4 Newtons

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35
Q

Definition of mass…

A

The quantity of matter.

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36
Q

Defenition of weight…

A

A measure of the gravitational pull of the earth.

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37
Q

Equation for Weight…

A

Weight = mass X gravity

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38
Q

Equation for mass…

A

Mass = weight
———
Gravity

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39
Q

Gravity = ? m/s^2

A

9.8m/s^2

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40
Q

Tension

A

The force of pulling apart.

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41
Q

Compression.

A

A crushing force.

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42
Q

Torsion

A

A twisting force.

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43
Q

Shear

A

Two materials sliding over another.

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44
Q

Bending

A

Combination of compression and tension.

Outside material: Tension
Inside material: Compression

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45
Q

Equation for stress:

A

Stress = Force
———
Area

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46
Q

Si Unit for stress…

A

N/m^2

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47
Q

Hooke’s Law

A

A strain in a solid is proportional to the applied stress within the elastic limit of that solid

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48
Q

Spring force equation…

A

Spring force = Spring constant X Spring stretch or compression

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49
Q

Proportional limit

A

The point at which the deformation is no longer directly proportional to the applied force.

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50
Q

Strain equation

A

Strain = Deformation
——————
Original Length

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51
Q

Si Unit for Strain…

A

Strain has no unit as it is a ratio

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52
Q

Young’s modulus equation

A

Young’s modulus = Stress
———
Strain

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53
Q

What is Young’s modulus?

A

Young’s modulusmeasures the resistance of a material to elastic (recoverable) deformation under load.

A stiff material has a highYoung’s modulusand changes its shape only slightly under elastic loads (e.g. diamond).

A flexible material has a lowYoung’s modulusand changes its shape considerably

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54
Q

What is bulk modulus?

A

The change in volume of a solid substance as the pressure on it is changed.

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55
Q

Bulk modulus equation…

A

Bulk modulus = Pressure
———————-
Volumetric strain

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56
Q

What is Poissons ratio?

A

The ratio of transvere strain to the axial strain in a stressed member.

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57
Q

Si Unit for Force…

A

Newton

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58
Q

Force =

A

Area X Pressure

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59
Q

Pressure =

A

Force
———
Area

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60
Q

Pascals Law:

A

A pressure change at an point in a confined incompressible fluid is transmitted throughout the fluid such that the same change occurs everywhere.

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61
Q

Density Equation:

A

Density = Weight
————
Volume

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62
Q

Si Unit for Density:

A

Kg/m^3

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63
Q

What is creep?

A

The tendency of a solid material to move slowly or deform permanently under the influence of persistent mechanical stresses.

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64
Q

Name of converting: Liquid to gas

A

Evaporation

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65
Q

Name of converting: gas to liquid

A

Condensing

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66
Q

Name of converting: solid to liquid.

A

Melting

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67
Q

Name of converting: Liquid to solid.

A

Freezing

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68
Q

Definition for atmospheric pressure.

A

The entire mass of the air that surrounds earth.

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69
Q

Two ways of measuring atmospheric pressure:

A

Mercury Barometers and Aneroid Barometer

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70
Q

5 Basic components of a hydraulic system:

A 
Reservoir
Pump or compressor
Lines (pipes)
Directional control valve
Actuating device
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71
Q

How does a Mercury barometer work?

A

Mercury in the tube adjusts until the weight of the mercury column balances the atmospheric force exerted on the reservoir, then giving a reading.

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72
Q

Equation for pressure:

A

Pressure = pgh

p = density
g = Gravity (9.8)
h = Height
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73
Q

How does a aneroid barometer work?

A

Uses a accumulation chamber (aneroid cell) made from beryllium and copper, held together with a spring, changes in atmospheric pressure changes cause the cell to expand or contract which gives a reading.

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74
Q

What is Archimedean principle?

A

A body submerged in a liquid displaces a volume of water equal to its own volume.

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75
Q

If a body is less dense than the fluid it will……

A

Float

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76
Q 
SUVAT equation:
t = 
u = 
v = 
a =
s =
Vav =
A 
t = Time
u= Initial velocity
v = Final velocity
a = Acceleration
s = Distance covered
Vav = Average Velocity
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77
Q

SUVAT Equation: a =

A

a = v-u
——
t

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78
Q

SUVAT Equation: Vav =

A

Vav = u+v
——
2

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79
Q

SUVAT Equation: v =

A

V = u+at

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80
Q

Symbol for angular velocity:

A

W

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81
Q

Tangential acceleration =

A

R X A

Radius X Angular Acceleration

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82
Q

What is Simple harmonic motion?

A

Motion which repeats itself precisely

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83
Q

Periodic Motion: T =

A

T = 1/F

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84
Q

Periodic Motion: F =

A

F = 1/T

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85
Q

Natural frequency of oscillation (Fn) =

A

Fn = 1
—- X square root of: K/M
2pi

K= The stiffness of the spring
M = The mass of the oscillating body
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86
Q

Definition of Period:

A

The time required to complete a full cycle

(T) in seconds

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87
Q

Definition of frequency:

A

The number of cycles per second

f) in hertz (Hz

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88
Q

Definition of amplitude:

A

The maximum displacement from equilibrium

A

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89
Q

Properties of simple harmonic motion (SHM)

A
  • The velocity and acceleration of the body is always changing
  • When velocity = 0, Acceleration = Maximum
  • When Acceleration = 0, Velocity = Maximum
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90
Q

Definition of free vibration:

A

Occurs when a mechanical system is set off with an initial input and then allowed to vibrate freely. Eg. A play swing

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91
Q

Definition of forced vibration:

A

When an alternating force or motion is applied to a mechanical system. Eg. A washing machine due to imbalance

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92
Q

Work done =

A

Work done = Force X Distance

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93
Q

Definition of Actual mechanical advantage (AMA):

A

The ratio of the output force to the input force.

This tells us how much easier it is for the worker

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94
Q

Definition of Ideal mechanical advantage (IMA):

A

The mechanical advantage that would exist if there where no friction in the machine.

(The ratio between input distance and output distance)

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95
Q

AMA =

A

Fo/Fi

Fo = Force output
Fi = Force input
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96
Q

IMA =

A

IMA = Di/Do

Di = Distance input
Do = Distance output
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97
Q

Definition of Efficiency (Eff):

A

The ratio of the output work to the input work

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98
Q

Eff =

A

Eff = Wo/Wi

or

Eff = Fo X Do
————-
Fi X Di

Wo = Work output
Wi = Work input
F = Force
D = Distance
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99
Q

How is efficiency expressed?

A

A percentage or a decimal

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100
Q

What is the pivot point known as on a lever?

A

The fulcrum

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101
Q

Lever IMA =

A

IMA = Li/Lo

Li = Distance from the input end of the lever to the fulcrum
Lo = Distance from the output end of the lever to the fulcrum
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102
Q

1st class lever

A

The fulcrum is between the load and the applied force. Eg. Scissors

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103
Q

2nd class lever

A

The load is between the fulcrum and the applied force. Eg. Wheelbarrow

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104
Q

3rd class lever

A

The applied force is between the load and the fulcrum. Eg. Ice tongs.

The IMA is less than one. There is no force advantage, however there is a speed advantage, the work can be done in less time.

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105
Q

Pulleys IMA =

A

The number of strands supporting the load

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106
Q

Pulleys: The length of the pulley cord (Di) =

A

2 X the distance raised (Do)

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107
Q

Wheel and axle IMA =

A

IMA = R/r

R = Radius of the wheel
r = Radius of the axle
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108
Q

Inclined plane IMA =

A

IMA = 1/ Sin(-0)

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109
Q

Screw jack: What is the pitch (p) of the screw?

A

The distance between threads

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110
Q

Screw jack IMA =

A

IMA = 2 pi r
——-
P

r = Radius
P = Pitch
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111
Q

Hydraulic press IMA =

A

IMA = R^2 / r^2

R = Larger piston radius
r = Smaller piston radius
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112
Q

Newton’s first law:

A

Law of inertia

A body at rest remains at rest and a body in motion continues to move at constant velocity unless acted upon by an unbalanced force

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113
Q

Newton’s second law:

A

To have a change in speed or direction an unbalanced force must act on the object.

F=MA

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114
Q

Newton’s third law:

A

Every action has an equal and opposite reaction.

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115
Q

What is centripetal force?

A

A force that action a body moving in a circular path and is directed towards the centre around which the body is moving.

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116
Q

Centripetal acceleration equation:

A

Velocity^2
————-
Radius

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117
Q

What is static friction?

A

The force between two objects that are not moving relative to each other.

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118
Q

What is limiting friction?

A

The maximum value of static friction when motion is impending.

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119
Q

What is rolling friction?

A

The frictional force associated with the rotational movement of a wheel or circular object along a surface. EG. A car wheel

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120
Q

What is kinetic friction (Dynamic friction)?

A

Occurs when two objects are moving relative to each other and rub together.

Usually does negative work, slowing something down.

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121
Q

Two types of kinetic friction…

A

Sliding friction

Fluid friction - Friction between a solid object as it moves through a liquid or gas

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122
Q

Kinetic energy (KE) equation:

A

1/2 MV^2

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123
Q

Definition of kinetic energy:

A

Energy which a body possesses by virtue of being in motion

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124
Q

Potential energy (PE) equation:

A

mgh

Mass x gravity x height

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125
Q

Definition of potential energy:

A

The energy possessed by a body by virtue of its position relative to others, stresses within itself, electric charge and other factors.

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126
Q

Defenition of power:

A

The rate of doing work

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127
Q

Equation for power:

A

Work/time

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128
Q

Definition of momentum:

A

The quantity of motion of a moving body.

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129
Q

Equation for momentum:

A

Mass X Velocity

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130
Q

Equation for inelastic collisions:

A

m1v1 + m2v2 = (m1+m2) V

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131
Q

Definition of inelastic collision:

A

A collision in which kinetic energy is not conserved due to the action of internal friction.

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132
Q

Definition of elastic collision:

A

Collisions that occur between bodies that deform very little in the collision. Therefore we assume no energy is lost and both kinetic and momentum are conserved.

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133
Q

Equation for elastic collision:

A

V1 - V2 = V2-V1

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134
Q

Torque definition:

A

Torque is the force applied to a body that is pivoted at a point that tends to cause a rotation around the pivoted point.

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135
Q

Equation for torque:

A

Torque = Radius X Force X sin$

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136
Q

Extension of a torque wrench: Scale reading =

A

Specified torque X L/ L+X

L = Distance between the driving tang and the centre fo the handle
X = Length of extension spanner between centres
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137
Q

Forces: What is a couple?

A

A pair of forces of magnitude that are equal and opposite but applied at points separated by a distance perpendicular to the forces. The combined moment of the forces produces a torque on the object they act on. EG. Taping. Hole

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138
Q

Equation for torque applied by a couple:

A

One of the forces (F) X distance to centre of rotation (r) X 2

Or

One fo the forces (F) X distance between the force (d) = FD

139
Q

Where is an earth gyro used?

A

Artificial horizons and altitude indicators

140
Q

What is differential pressure?

A

The maximum difference between cabin pressure and atmospheric pressure which the pressurisation system can sustain.

141
Q

What does the term “saturated” mean?

A

When the air contains the maximum amount of vapour possible for a particular temperature.

Warm air can hold more vapour then cold air

142
Q

What is absolute humidity? What is its unit?

A

The amount of water vapour that is present in a unit plume of air.

Expressed in grams per cubic meter

143
Q

What is relative humidity?

A

The amount of water vapour actually in the air divided by the amount of water vapour the air can hold.

144
Q

If unsaturated air is cooled, relative humidity ……

A

Increases

145
Q

What is dew point?

A

The temperature air would have to be cooled to in order for saturation to occur

146
Q

What is actual vapour pressure? What is it measured in?

A

The partial pressure exerted by the water vapour present in a parcel.

Measured in Millibars

147
Q

What is condensation?

A

The phase change of a gas to liquid.

148
Q

What us dry bulb temperature?

A

The actual air temperature

149
Q

What is mixing ratio?

A

The mass of water vapour in a parcel divided by the mass of the dry air in the parcel. (Not including water vapour)

150
Q

What is saturation to air?

A

The condition under which the amount of water vapour in the air is the maximum possible at the existing temperature and pressure.

151
Q

What is the saturation vapour pressure?

A

The maximum partial pressure that water vapour molecules would exert if the air were saturated with vapour at a given temperature.

152
Q

What is specific humidity?

A

The mass of water vapour in a parcel divided by the total mass of the air in the parcel. (Including water vapour)

153
Q

What is sublimation?

A

The transition from sold to gas.

154
Q

What is the wet bulb temperature?

A

The lowest temperature that can be obtained by evaporating water into the air at constant pressure.

155
Q

What is specific gravity?

A

The ratio of the density of a substance to the density of a given reference material.

(No unit as it is a ratio)

156
Q

Specific gravity equation:

A

Density of the substance/ Density of water

157
Q

What is the density of water?

A

997 kg/m^3

158
Q

What is ideal fluid/inviscid fluid?

A

A fluid which has no resistance to shear stress

159
Q

What is dynamic viscosity?

A

Determines the dynamics of an incompressible fluid

160
Q

What is kinematic viscosity?

A

The dynamic viscosity divided by the density

161
Q

What is volume viscosity/ bulk viscosity?

A

Determines the dynamic of a compressible fluid

162
Q

What is a non-Newtonian?

A

Fluids without a constant viscosity, there viscosity cannot be described by a single number

163
Q

Most common type of Viscometer?

A

Glass capillary viscometer

164
Q

Name the 4 types of viscometer?

A

Glass capillary
Zahn cup
Stormer (measured in kerbs, unique to the stormer)
Vibrating viscositors

165
Q

Kinematic viscosity equation:

A

Dynamic viscosity/ density

166
Q

Viscosity of water at 25 degrees:

A

8.90 x 10^-4 pa

167
Q

Profile drag includes:

A

Form drag
Interference drag
Skin friction

168
Q

Wave drag occurs when…..

A

A solid object is moving through a fluid at or near the speed of sound in that fluid

169
Q

Drag equation:

A

Coefficient x (density x velocity^2) x reference area
—————————-
2

170
Q

Drag coefficient equation:

A 
Drag
—————-
Density x area x v^2
                               ——
                                   2
171
Q

Viscosity equation:

A

-BV

B = Constant that depends on the properties of the fluid and the dimensions of the object

V = The velocity of the object

172
Q

Definition fo drag coefficient:

A

A dimensionless quantity that describes a characteristic amount of aerodynamic drag caused by fluid flow.

173
Q

What is the Bernoulli principle?

A

An increase in speed of a fluid occurs simultaneously with a decrease in static pressure or a decrease in the fluids potential state.

174
Q

Venturi principle:

A

The reduction in fluid pressure that results when a fluid flows through a constricted section of a pipe, but velocity increases.

175
Q

What is a Newtonian fluid?

A

Where stress is directly proportional to rate of strain or fluid with a constant viscosity at a fixed temperature or pressure

176
Q

Angle of attack:

A

The angle between the chord line of the wig and the relative wind direction

177
Q

Boundary layer:

A

A thin layer of air in direct contact with the wing surface, which due to friction is actually stationary (relative to the wing)

178
Q

Freezing point of water:

A

0 degrees Celsius

32 degrees Fahrenheit

179
Q

Absolute zero:

A

If we cool any substance enough we can cause all molecular motion to cease.

180
Q

Conventions: centigrade to kelvin

A

K = C + 273

181
Q

Conversion: Fahrenheit it rankin

A

R = F + 460

182
Q

Boyles law:

A

The pressure of a given ,ass of an ideal gas is inversely proportional to its volume at a constant temperature.

183
Q

Boyles law equation:

A

P1V1=P2V2

184
Q

Charles Law:

A

The volume of an ideal gas at constant is directly proportional to the absolute temperature

185
Q

Charles law equation:

A

V1/T1 = V2/T2

186
Q

Gay-lussacs law:

A

The pressure of a given mass of gas varies directly with the absolute temperature of the gas, when the volume is kept constant.

187
Q

Gay-lussacs law equation:

A

P1/T1 = P2/T2

188
Q

Compressor discharge pressure (CDP):

A

The pressure of the air when it leaves the compressor

189
Q

Compression ration equation:

A

Compression ratio = CDP/CIP

CDP - Compressor discharge pressure
CIP - Compressor inlet pressure

190
Q

Coefficient of linear expansion:

A

Used to account for different rates of materials (Unit = degrees Celsius)

191
Q

Coefficient of linear expansion equation:

A

^L=a Lo ^T

^L = Change in temperature 
a = coefficient of linear expansion 
Lo = original length of the rod
^T = Change in temperature
192
Q

The temperature of a body is …..

A

A measure of the average kinetic energy of the molecules of that body.

193
Q

Two dimensional area thermal expansion equation:

A

^A = 2a Ao ^T

^A = change in area of the body
^T the change in temperature
Ao = Original area of the body
a = The coefficient of linear expansion

194
Q

Three dimensional volume thermal expansion equation:

A

^V = 3 a Vo ^T

Vo = Original volume of the body
a = Coefficient of linear expansion
^V = Change in volume of the body
^T = Change in temperature
195
Q

What happens to water between 0 and 4 degrees Celsius?

A

It expands when cooled

196
Q

1 Calorie = ? J

A

4186J

197
Q

1 BTU = ? Calories

A

0.252 Calories

198
Q

Heat gained or lost equation:

A

Q = m C ^T

Q= heat gained or lost (J)
M = mass of the body (KG)
C = The specific heat of the substance (J/kg Degrees Celsius)
^T = The temperature change (Degrees Celsius or Kelvin)
199
Q

Latent heat:

A

The energy required to change the phase of a substance.

200
Q

Latent heat energy required equation:

A

Q=ML

Q= Latent heat energy required 
M = Mass
L = Specific latent heat of fusion or evaporation
201
Q

Each time water changes state …..

A

Energy is absorbed or released

202
Q

Convection:

A

The transfer of heat by the actual movement of the warmed matter.

203
Q

Conduction:

A

The transfer of energy through matter from particle to particle.

204
Q

Radiation:

A

Electromagnetic waves that directly transport energy through space.

205
Q

Refrigeration:

A

The removal and relocation of heat.

206
Q

4 components of a refrigeration system:

A

Compressor
Condenser
Metering device
Evaporator

207
Q

Heat pump:

A

A device that moves heat from one location to another using work.

208
Q

What type of process is Boyles law?

A

Isothermal (Temperature)

209
Q

What type of process is Charles law?

A

Isobaric (Pressure)

210
Q

What type of process is Gay-Lussac’s Law?

A

Isochoric (Volume)

211
Q

Adiabatic:

A

When a change in the volume and pressure of the contents of a system takes place without exchange of heat between the system and its surroundings.

212
Q

Which gas laws are Adiabatic?

A

Boyles law - ?
Charles law - Not Adiabatic
Gay Lussacs law - Not Adiabatic

213
Q

Thermodynamics: Work done by a piston equation:

A

Work = Pressure X Change in volume

214
Q

Internal Energy (u)

A

Energy contained in a system

Measured in Joules

215
Q

Enthalpy

A

The sum of the internal energy added to the product fo the pressure and volume of a system.

(H)

216
Q

Enthalpy Equation:

A

H = E + PV

H = Enthalpy 
E = Internal Energy
P = Pressure
v = Volume
217
Q

1st law of thermodynamics:

A

The internal energy (E) of a system tends to increase, if energy is added as heat (Q) and trends to decrease if energy is lost as work (w) is done by the system.

218
Q

Heat energy added to the system (Q) =

A

Work done by the system (w) + Change in internal energy (u)

219
Q

2nd law of thermodynamics

A

The total entropy of an isolated system can never decrease over time and is constant if and only if all processes are reversible.

220
Q

Thermal efficiency equation:

A

Thermal efficiency = 1 - temperature of cold source/temperature of hot sauce

221
Q

Isentropic process:

A

An idealised thermodynamic process that is both adiabatic and reversible.

222
Q

3rd law of thermodynamics:

A

The entropy of a system at absolute zero is a well defined constant.

223
Q

Entropy:

A

A quantity representing the unavailability of a systems thermal energy for conversion into mechanical work.

224
Q

Speed of light:

A

3.00 x 10^8 m/sec

225
Q

What range are visible lights?

A

4,000A (Ultraviolet) - 7,000A (Infrared)

226
Q

Speed of electromagnetic radiation (c) equation:

A

C= Frequency (f) X wavelength

227
Q

What two types of waves for EM radiation consist of?

A

An electrical field (E field) and a magnetic field (B field), moving at 90 degrees to each other.

228
Q

Index of radiation (n) equation:

A

n = Speed of light in free space (C)/speed of light in the substance (v)

229
Q

Index of refraction:

A

The ratio of the speed of light in a vacuum to the speed of light in the substance.

230
Q

Can electromagnetic waves travel through opaque materials containing free electrons and why?

A

No as the waves lose so much energy to the electrons.

231
Q

Refraction:

A

The change in direction of a wave passing from one medium to another (Occurs when at an angle other than 90 degrees)

232
Q

Chromic Aberration:

A

A failure of a lens to. Focus all colours to the same point. It is cause be dispersion.

233
Q

Dispersion:

A

The phenomenon in which the phase velocity of a wave depends on its frequency.

234
Q

Converging/ positive lens:

A

Alters a plane wavefront to make the light waves pass through a point or focus.

235
Q

Smells law:

A

A formula used to describe the relationship between the angles of incidence and reflection.

236
Q

Snells law equation:

A

N1 X sin$ 1 = N2 X sin$2

N1 = Incident index
$1 = Incident angle 
N2 = Refracted index 
$2 = Refracted angle
237
Q

Focus/principle focus:

A

The point on the axis of a lens which parallel rays of light converge or from which they appear to diverge after refraction or reflection.

238
Q

Focal length:

A

Distance from principle focus to the centre of the lens

239
Q

Aberration:

A

A departure of an image forming optical system from ideal behaviour.

240
Q

Finding the image by formula, Lens formula:

A

1/U +1/V = 1/F

U= Distance of the object from the lens centre 
V = Distance of the image from the lens centre
F = Focal length of the lens
241
Q

Which is positive and which is negative?

Diverging lens & Converging lens

A 
Diverging lens (-f)
converging lens (+f)
242
Q

Lens power =

A

1/F

F=Focal length of the lens

243
Q

Unit of lens power:

A

Dioptre (D)

244
Q

Front silvered mirrors:

A
  • Metallic layer on the front surface.
  • Very fine metal particles are deposited on glass either from solution or from metal vapour in a vacuum
  • large mirrors used in reflecting telescopes are made this way
  • Metal surfaces are easily damaged
245
Q

Reflecting Prisms:

A

A glass (or clear plastic) reflecting prism provides a cheap and practical plane mirror by using the effect of total internal reflection.

246
Q

How does internal reflection occur?

A

Internal reflection occurs when the angle of incidence of a ray exceeds the critical angle (c) for the medium.

247
Q

Principle axis:

A

A line passing through the centre of the sphere and attaching to the mirror in the exact centre of the mirror.

248
Q

Centre of curvature (c):

A

The point in the centre of the sphere from which the mirror was sliced.

249
Q

Vertex (A):

A

The point on the mirrors surface where the principle axis meets the mirror. (Geometric centre of the mirror)

250
Q

Focal point (F):

A

Midway between the vertex and the centre of curvature.

251
Q

Radius of curvature (R):

A

The distance from the vertex to the centre of curvature.

252
Q

Focal length:

A

Distance from the mirror to the focal point.

253
Q

Why are convex mirrors used, and where are they used?

A

Used to fit more detail into the mirror by shrinking it. EG. Car mirror

254
Q

Fibre optics:

A

Uses light to send information (data)

255
Q

Three basic functions of fibre optics:

A

Transmitter: Convert an electrical input signal to an optical signal.
Optical fibre: Transport the optical signal.
Receiver: To convert the optical signal back to an electrical signal.

256
Q

Transmitter consists of what two components?

A

An interface circuit and a source drive circuit.

257
Q

Fibre optics: What does a transmitter drive circuit do?

A

Converts the electrical signals to an optical signal, it does this by varying the current flow through the light source.

258
Q

Fibre optics: Two types of optical sources:

A

Light emitting diodes (LED’s) and laser diodes

259
Q

Fibre optics: What does the optical source do?

A

The optical source launches the optical signal into the fibre.

260
Q

Fibre optics: What does the receiver consist of?

A

The optical sector and the signal conditioning circuits.

261
Q

Fibre optics: What does the signal conditioning circuit do?

A

The signal conditioning circuit condition the detector output so that the receiver output matches the original input to the transmitter.

262
Q

Fibre optics: An optical sector can either be:

A

A semi conductor positive intrinsic negative (PIN) or an avalanche photodiode (APD)

263
Q

Name some advantages of fibre optics:

A
  • System performance
  • No crosstalk
  • Immunity to noise (EMI & RFI)
  • Difficult to tap
  • Lower bit error rates
  • Signal security
  • Reduced size and weight
  • Resistant to radiation and corrosion
264
Q

Negatives of fibre optics:

A
  • Expensive
  • Lack of standardisation
  • Company’s are used to electrical and do not want to switch
265
Q

Bandwidth:

A

The amount of information that can be transmitted at one time.

266
Q

How does frequency effect bandwidth?

A

The higher the frequency the greater the bandwidth.

267
Q

What type of light is generally used for fibre optics?

A

Infrared

268
Q

3 Parts structure of fibre optics:

A

The core
Cladding
Coating of buffer

269
Q

What is the core of a fibre optics cable made from?

A

A Dialectic material. (conducts no electricity)

Generally Glass

270
Q

What is the purpose of the cladding in fibre optics? (4x answers)

A
  • Reduce loss of light from the core into the surrounding air
  • Reduces scattering loss at the surface of the core
  • Adds mechanical strength
  • Protects fibre from absorbing contaminants.
271
Q

What is the purpose of the coating or buffer on fibre optics?

A

To protect fro physical damage.

Also prevents scattering losses caused by microbends

272
Q

How is light described by ray law?

A

Light is described as a simple ray.

273
Q

Ray theory: Two types of rays that can propagate along an optical fibre:

A

Meridional rays and Skew rays

274
Q

Meridional rays:

A

Rays that pass through the axis of the optical fibre.

Used to illustrate the basic transmission properties of optical fibre

Classified into bound or unbound

275
Q

Skew rays:

A

Rays that travel through an optical fibre without passing through its axis.

276
Q

Bound rays:

A

Remain in the core and propagate along the axis of the fibre.

They propagate through the fibre by total internal reflection.

277
Q

Unbound rays:

A

Rays are refracted out of the fibre core.

278
Q

Acceptance Angle:

A

The maximum angle to the axis of fibre that light entering the fibre is propagated

(The value of the acceptance angle is dependent on the fibre properties and transmission conditions.

279
Q

Numerical Aperture:

A

A measurement of the ability of an optical fibre to capture light.

(The NA is also used to define the cone of acceptance of an optical fibre.)

280
Q

Numerical Aperture (NA) equation:

A

NA = no X Sin$a = (n1^2 - n2^2) X 1/2

281
Q

Mode theory:

A

Used to describe the propagation of light along an optical fibre.

(Used to describe the properties that ray the ray theory is unable to explain.)

282
Q

How does the mode theory describe the propagation of light along a fibre?

A

The mode theory uses electromagnetic wave behaviour to describe the propagation of light along a fibre.

283
Q

How is a plane wave described?

A

A plane wave is described by its direction, amplitude and wave length of propagation.

A plane wave is a wave whose surfaces of constant phase are infinite parallel planes normal to the direction of propagation.

284
Q

Wavelength of a plane wave equation:

A

Wavelength = C/fn

C = Speed of light in a vacuum
f = Frequency of the light 
n = Index of refraction of the plane wave medium
285
Q

Plane waves repeat at a distance equal to:

A

wavelength/sin$

286
Q

Cut-off wavelength:

A

The wavelength at which a mode ceases to be bound.

Which can be caused by a change in wavelength.

287
Q

Fundamental mode:

A

An optical fibre is always able to propagate at least one mode. This is known as the fundamental mode.

288
Q

Single mode fibre:

A

An optical fibre that operates above the cut-off wavelength.

At a longer wavelength

289
Q

Dispersion:

A

The change in the propagation constant for different wavelengths.

290
Q

Chromic Dispersion:

A

The change in the propagation constant for different wavelengths.

291
Q

Modal dispersion:

A

The change in propagation constant for different modes.

292
Q

Modes:

A

A set of guided electromagnetic waves.

293
Q

How is the order of each mode indicated?

A

The order of each mode is indicated by the number of field maxima within the core of the fibre.

294
Q

Transverse Mode:

A

A mode of electromagnetic radiation with a particular electromagnetic field pattern of radiation in the plane perpendicular to the radiations propagation direction.

295
Q

Cladding modes:

A

Modes that become trapped in the cladding region.

296
Q

Mode coupling:

A

The exchange of power between modes.

297
Q

Normalised Frequency:

A

Electromagnetic waves bound to an optical fibre are described by the fibres normalised frequency.

298
Q

What does the normalised frequency determine?

A

How many modes a fibre can support.

It is a dimensionless quantity.

299
Q

As the normalised frequency increases, the number of modes supported by the fibre …….

A

Increases

300
Q

Two types of optical fibre:

A

Single mode fibres

Multi mode fibres

301
Q

Single mode fibres:

A

Core size is small, diameter is around 8 - 10 micrometers

Allows only the fundamental or lowest order mode (around 1300 manometer wavelength)

302
Q

Which mode fibres have a lower signal loss and a higher bandwidth, Single mode or multi mode?

A

Single mode

303
Q

Multi mode fibres: As the number of modes increase the effect of modal dispersion …….

A

Increases

304
Q

Modal Dispersion:

And what does it effect?

A

Modes arrive at the fibre end at slightly different times. This time difference causes the light to spread. This effects the systems bandwidth.

305
Q

Attenuation:

A

Reduces the amount of optical power transmitted by the power.

Mainly as a result of light absorption, scattering and bending losses.

306
Q

Signal Attenuation:

A

The ratio of optical input power (Pi) to the optical output power (Po).

307
Q

Attenuation Equation:

A

(10/L) Log^10 (Pi/Po)

L = Length (KM)
Pi = Input power
Po = Output power
308
Q

Unit of attenuation:

A

Decibel/kilometre (dB/km)

309
Q

Absorption:

A

The portion of attenuation resulting from the conversion of optical power into another energy, EG. Heat.

310
Q

Absorption in optical fibres is explained by three factors:

A
  • Imperfections in the atomic structure of the fibre material
  • The intrinsic or basic material-material properties
  • The extrinsic material-material properties
311
Q

Intrinsic Absorption:

A

Caused by basic material-material properties. Intrinsic absorption sets the minimal level of absorption.

312
Q

Extrinsic Absorption:

A

Caused by impurities introduced into the fibre material. This causes an electronic transition of these metal ions from one energy level to another.

313
Q

Scattering:

A

Caused by the interaction of light with density fluctuations within a fibre.

Density changes are produced when the fibres are manufactured.

314
Q

Rayleigh Scattering:

A

Occurs when the size of the density function (Fibre defect) is less than 1/10th of the operating wavelength of light.

315
Q

As the wavelength increases, the loss caused by Rayleigh scattering …….

A

Decreases

316
Q

MIE Scattering:

A

Caused by these large defects in the fibre core, scatters light out of the fibre core.

Occurs if the size of the defect is greater than 1/10th of the operating wavelength of light.

317
Q

Bending Loss:

A

Bending the fibre also causes attenuation. Bending loss is classified according to the bed radius of curvature microbes loss or macrobend loss.

318
Q

Microbends:

A

Small microscopic bends of the fibre axis that occur mainly when a fibre is cabled. Caused by small imperfections in the fibre.

319
Q

Macrobends:

A

Bends having a large radius of curvature relative to the fibre diameter.

During installation if fibres are bent too sharply, macrobend losses will occur.

320
Q

Two types of dispersion in optical fibres:

A

Intramodal dispersion

Intermodal dispersion

321
Q

Intramodal dispersion:

A

AKA Chromiatic Dispersion

  • Depends on the fibre materials.
  • Categorised into material dispersion and wave guide dispersion
  • Occurs in all types of fibre
  • Occurs because different colours of light travel through different materials and different waveguide structures at different speeds
322
Q

Intermodal dispersion:

A

AKA Modal dispersion

  • Causes the input light pulse to spread.
  • The pulse spreads because each mode propagates along the fibre at different speeds and as a result travels a different distance in the same span.
323
Q

Which type of fibres exhibit the lowest amount of total dispersion but the highest amount of bandwidth?

A

Single mode fibres

324
Q

Analogue Transmission:

A

The incoming information signal is used to control the power output from the LED or the laser.

At the far end the receiver converts light to an electrical signal.

325
Q

Digital transmission:

A

The information signal is represented by a sequence of on/off levels. The “on” state is referred to as logic 1 and the “off” state as logo 0.

This approach means it ignores noise and distortion.

326
Q

Refractive Index Profile:

A

Describes the value of refractive index as a function of radial distance at any fibre diameter.

327
Q

Step - Index fibre:

A

The refractive index of the core is uniform and undergoes an abrupt change at the core-cladding boundary.

328
Q

Graded-Index Fibres:

A

Th refractive index of the core varies gradually as a function of radial distance from the fibre centre.

329
Q

Standard Core sizes:

Multimode step index
Multimode graded index
Single mode fibres

A

Multimode step index: 50 - 100 Micrometers
Multimode graded index: 50, 62.5, 85 & 100 Micrometers
Single mode fibres: 8 - 10 Micrometers

330
Q

Multimode step Index:

A
  • Large core diameters and NA

- Limited bandwidth capabilities

331
Q

Multimode graded index fibre:

A
  • Relatively high source to fibre coupling efficiency
  • Low loss
  • Low sensitivity to bending
  • High bandwidth
  • Expansion capability
332
Q

Two types of single mode step-index:

A

Matched cladding

Depressed Cladding

333
Q

Matched Cladding:

A

Means that the fibre cladding consists of a single homogeneous layer of dielectric material

334
Q

Depressed Cladding:

A

Means that the fibre cladding consists of two regions: The inner and outer cladding regions

335
Q

Single mode step-index fibre:

A
  • Low Attenuation

- High bandwidth properties

336
Q

Optical time domain reflectometer (OTDR):

A
  • Main field measurement technique, used for conducting field measurements on installed optical fibres of 20 meters or more in length.
  • Requires access to only one end
  • Measures attenuation
  • Identifies losses, breaks and faults.
337
Q

Optical Loss test set (OLTS):

A

Combines the power meter and source functions into one unit.

338
Q

Point Defect:

A

Temporary or permanent local deviation of the OTDR signal upward or downward direction.

  • Caused by connectors, splices or breaks along the fibre length.
339
Q

Optical power meter:

A

Measures fibre attenuation and transmission loss in the field. Used when the cable is less than 50 meters.

  • Must be connectors both ends
  • Uses a light source
340
Q

Intensity of sound (Decibels) Equation:

A

Decides = 10 log(intensities of the sound/ 10^-12)

341
Q

Heat required to change a liquid to a gas is called the heat of …….

A

Vaporisation.

342
Q

Centripetal force=

A

MV^2/r

343
Q

Constant velocity =

using gravity and height

A

V=square root of (2gh)

B licence Physics (2 decks)

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