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A-LEVEL 9702 物理要点
A-LEVEL 9702 物理的知识要点整理，本导图较大，因为涵盖了物理量、匀变速运动、牛顿三定律、力矩、公于能等31各章节的重点内容图文汇总，完整覆盖考试大纲，大家自取。
编辑于2023-02-13 15:19:46 福建省- A-LEVEL
- EEE229 Electrical Energy and Conversion
这是一篇关于EEE229 Electrical Energy and C的思维导图，主要内容包括：Synchronous machines 、电磁理论基础运动、DC电机、AC Asyn AC异步电动机、Synchronous machines & applications等。
- E118 electronic devices and circuits
大学的electronic devices and circuits课程笔记，知识点系统且全面，希望对大家有用。
- A-LEVEL 9702 物理要点
A-LEVEL 9702 物理的知识要点整理，本导图较大，因为涵盖了物理量、匀变速运动、牛顿三定律、力矩、公于能等31各章节的重点内容图文汇总，完整覆盖考试大纲，大家自取。
A-LEVEL 9702 物理要点
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- EEE229 Electrical Energy and Conversion
这是一篇关于EEE229 Electrical Energy and C的思维导图，主要内容包括：Synchronous machines 、电磁理论基础运动、DC电机、AC Asyn AC异步电动机、Synchronous machines & applications等。
- E118 electronic devices and circuits
大学的electronic devices and circuits课程笔记，知识点系统且全面，希望对大家有用。
- A-LEVEL 9702 物理要点
A-LEVEL 9702 物理的知识要点整理，本导图较大，因为涵盖了物理量、匀变速运动、牛顿三定律、力矩、公于能等31各章节的重点内容图文汇总，完整覆盖考试大纲，大家自取。
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A-LEVEL物理9702要点
1章 物理量
标量 scalar
a scalar has magnitude only
例
work
energy
temperature
矢量 vector
a vector has magnitude and direction
例
velocity
acceleration
force
momentum
矢量和标量都具有的属性
magnitude
unit
2章 匀变速运动
概念
位移 displacement
distance from a fixed point in a particular direction
距离 distance
比较displacement与distance的异同点
相同点: both have magnitude and unit
差异点
distance
scalar, no direction
displacement
vector, has direction
速度 velocity
the rate of change of displacement
change in displacement / time
是矢量，有方向
v-t曲线的积分就是displacement
速率 speed
the rate of change of distance
标量，无方向
加速度 acceleration
the rate of change of velocity
是一个矢量，有方向
加速度是速度-时间图的曲线斜率
力 Force
the rate of change of momentum
重力 weight
the gravitational force
质量 mass
measure of body's resistance to change in motion
公式
匀变速运动的几种典型
从零开始的匀变速运动
自由落体运动
竖直方向上初速为零的匀变速运动，加速度为g
上抛运动
初速度不为零，匀变速运动，加速度为g（与初速度方向相反）
炮弹发射（不计空气阻力）
水平方向为匀速运动；竖直方向为上抛运动；两者的叠加
3章 牛顿三定律
第一定律
合力为0时，物体保持静止或匀速直线运动
an object will remain at rest or keep travelling at constant velocity unless it is acted on by a resultant force
a body continues at rest or constant velocity unless acted upon by a resultant force
物体保持平衡态的条件
resultant force is zero
resultant moment is zero
If a body is in equilibrium, there is no resultant force and no resultant torque or moment about any point
第二定律
F=ma
the resultant force is equal to the rate of change of its momentum.
force proportional to rate of change of momentum
重要的力的形式
推力push或拉力pull
重力weight
（g=9.81)
沿斜坡的重力分力=G·sinθ
摩擦力 friction
空气阻力 drag
浮力 upthrust
接触力 contact force
（绳子或弹簧）张力 tension
第三定律
两个物体间的作用力，作用力与反作用力大小相等，方向相反
when two bodies interact, the forces they exert on each other are equal and opposite
3.7 SI单位与单位量级
SI基本单位为
其他单位可以从基本单位按照公式进行推导
常见单位
常见单位的量级
4章 力矩
概念
力矩 moment
the product of force and the perpendicular distance from the pivot to the force
Force * distance from pivot
重心 centre of gravity of a body
the point where all the weight of the body is taken to act
公式与原理
力矩原理 The principle of moments
for a body in (rotational) equilibrium， the sum of the clockwise moments about any point equals the sum of the anticlockwise moments about that same point
5章 功与能
概念
功 work
the product of the force and the distance moved in the direction of the force
WORK= force × distance moved in the direction of the force
w=Fs , force × displacement
力与运动方向不一致，可以把力进行分解为沿运动方向以及垂直运动方向的分力
力与位移的夹角
动能 Kinetic energy
energy possessed by a mass due to its motion
重力势能 Gravitational potential energy
energy possessed by a mass due to its position in a gravitational field
功率 单位 W（Js-1）、KW、MW
公式及定理
动能 kinetic energy
work done by force 力所做的功转化为物体的动能
重力势能 gravitational potential energy
能量守恒
principle of conservation of energy：Energy cannot be created or destroyed. It can only be converted from one form to another
能量守恒的一个例子：重力势能变化=动能变化
光滑斜坡或摆动小球
燃油车20%转化为车的动能，其他80%转化为热散失在环境中
功率一定的情况下，力与速度成反比
6章 动量与冲量
概念
动量 momentum
the product of mass and velocity
公式及定理
动量 momentum
mass × velocity
动量是矢量，有方向，符用矢量加法
冲量
冲量等于物体动量的变化
动量守恒定律The principle of conservation of momentum
没有外力作用下的弹性碰撞，碰撞前总动量与碰撞以后总动量相等
in a closed system, the total momentum before is equal to the total momentum after.
We have to consider objects that form a closed system–that is, no resultant external force acts on them. The principle of conservation of momentum states that, within a closed system, the total momentum in any direction is constant.
碰撞分类
弹性碰撞 Elastic collision
total momentum is conserved and total kinetic energy is conserved
In a perfectly elastic collision of two bodies, the relative speed of the body’s approach is equal to the relative speed of their separation. 碰撞前相对速度等于碰撞以后相对速度
公式
非弹性碰撞inelastic collision
动能部分或全部转换为其他形式的能（比如热或声音）
7章 密度 压力 浮力
概念
密度 density
mass / volume
mass per unit volume
压强
the normal force per unit cross-sectional area
normal force / cross-sectional area
浮力
液体上下压强差导致的
the pressure on the lower surface is greater than the pressure on the upper surface
公式
密度公式
m质量 V体积
压强公式
F 垂直压力 A受力面积
液体压强
浮力公式
V 排开液体体积
7章 胡克定律与弹性形变
公式
limit of proportionality
This is the point beyond which the extension is no longer proportional to the force
elastic limit
The force beyond which the spring becomes permanently deformed is known as the elastic limit
几个公式间关系
Young Moudlus仅与材料有关，与粗细无关,E的单位为Pa （N.m-2）
弹性形变势能
8-11章 电路
概念
电阻 R resistance
potential difference / current
电压 U 伏特
joule per coulomb
电流 I 安培
charge=current * time
公式&定律
重要公式
电流公式的另外一种表达
A截面积 cross-sectional area； n为与材料相关，导体导电子密度，number density of free electrons v为粒子飘移速度， q为带电粒子电荷量，对于电子而言，为1
Kirchhoff’s first law
the sum of the currents entering any point is equal to the sum of the currents leaving that same point
Kirchhoff’s second law
the sum of the e.m.f.s round a closed loop in a circuit is equal to the sum of the p.d.s in that same loop
e.m.f. of battery = sum of p.d.s across the resistors
从能量角度做解释
energy gained passing through sources of e.m.f. = energy lost passing through components with p.d.s
energy gained per coulomb around loop = energy lost per coulomb around loop
欧姆定律 ohm's law
适用于通常的电阻
热敏电阻 Thermistors
仅需要掌握NTC Thermistors
电阻随温度升高而降低
light-dependent resistor (LDR) 光敏电阻
随着光照，电阻减小
A typical LDR will have a resistance of a few hundred ohms in sunlight, but in the dark its resistance will be millions of ohms
二极管、LED
Most modern diodes are made from silicon and will start conducting when there is a potential difference of about 0.6 V across them. You need to remember this key 0.6 V value.
通常金属导体的电阻
随温度上升，R略微上升
非春金属，其电阻比春金属要高
电阻公式
ρ为导体材料的电阻率；l为导体长度；A为导体面积
电阻率计算
测量电池电势与内阻
实验图
关键公式
12章 波
波的基本参数
progressive wave
Waves that move through a material (or a vacuum) are called progressive waves
A progressive wave transfers energy from one position to another.
纵波 longitudinal waves
the particles of the medium vibrate parallel to the direction of the wave velocity
横波 transverse waves
the particles of the medium vibrate at right angles to the direction of the wave velocity
波长 wavelength （ λ ）
distance between two adjacent wavefronts
周期 period （T)
time for one cycle
振幅 amplitude （A)
the maximum displacement
displacement
distance from the equilibrium position
频率 frequency （f）
The number of oscillations per unit time of a point in a wave is called its frequency f
波速 speed （v）
It is important to realise that, for both types of mechanical wave, the particles that make up the material through which the wave is travelling do not move along – they only oscillate about a fixed point. It is energy that is transmitted by the wave
强度 intensity （I）=power/area
(I 正比于振幅的平方)
相位 Phase
相位差 =x/l *360°
多普勒效应
靠近时听到的频率比初始频率高
远离时听到的频率比初始频率低
多普勒效应描述
The pitch is higher as the vehicle approaches you, and lower as it moves away (recedes). This is an example of the Doppler effect
说明
fs为初始频率
v是波速
vs是相对移动速度
f0为接受者感觉到的频率
靠近用减；远离用加
电磁波
Polarisation
Malus’s law
13章 波的叠加 Superposition
叠加原理 principle of superposition
when waves meet at a point，resultant displacement is sum of individual displacements
coherent wave
有固定的相位差（即有相同的频率）
constant phase difference / same frequency
双缝干涉实验
公式
格栅实验
公式
d为格栅间距
θ为距离中心的角（最大为90度）
n为第几个亮线条（中心亮线n=0）
14 章 静止波 stationary wave
形成条件
two progressive waves of the same amplitude and wavelength, travelling in opposite directions, superpose
两个progressive波有相同的振幅，周期（波长），沿相反方向传播叠加产生
stationary wave 与 progressive wave区别
progressive wave transfer energy
stationary wave don't transfer energy
node
point do not moved
antinoe
point with maximum amplitude
特点
node两侧的相位差180度
两个node之间所有位置相位一致
15章 核物理
α散射实验
结论
原子组成
元素表达方法
重要的粒子
夸克模型
亚原子基本微粒分类
Leptons (轻子） such as electrons and neutrinos. These are particles that are unaffected by the strongnuclear force.
Leptons are (currently) considered to be fundamental particles
Hadrons（重子） such as protons and neutrons. These are all particles that are affected by the strong nuclear force
hadron包括
baryons（重子）
three quarks make up a class of hadrons called baryons
proton = (uud).
neutron = (udd).
mesons（介子）
a quark and an antiquark make up a class of hadron called
核力
strong nuclear force 强核力
a short range force that holds the nucleons in a nucleus together. It is a force that is felt only by hadrons, not leptons 把质子中子捏合在一起形成原子核的力，对轻子不起作用，短距离起作用
weak nuclear force 弱核力
It is felt by both hadrons and leptons
it is the interaction that causes β-decay
a hadron changes to a different hadron with the emission of a lepton and an antilepton
β-衰变
原子核里面的中子neutron变为质子proton（夸克d-->u），释放一个电子electron和一个反中微子antineutrino
原子序数增加1
β+衰变
质子变中子（u-->d），释放一个正电子（position），和一个中微子neutrino
原子序数减1
P1 误差 准确度 精确度 不确定性
系统性错误 systematic error
systematic errors can be corrected
例子 zero error
– The zero on a ruler might not be at the very beginning of the ruler
随机错误 Random errors
Random errors can be reduced by making multiple 2 ab 3measurements and averaging the results
例子 reading scale from different angles
精确度 precision
the range of the values
准确性 accuracy
the closeness of the value to the true value
不确定性 uncertainty
The uncertainty, however, is an actual range of values around a measurement
uncertainty计算原则
16章 匀速圆周运动
关键公式
匀速圆周运动典型
火车/汽车拐弯
钟摆
旋转
卫星绕地运动
行星（如地球）围绕太阳转
月亮绕地球转
17章 重力场
重力场 gravitational field
The arrows on the field lines show us the direction of the gravitational force
The spacing of the field lines indicates the strength of the gravitational field
牛顿万有引力定律 Newton’s law of gravitation:
G is sometimes referred to as the universal gravitational constant 6.67 × 10−11 N m2 kg−2
重力加速度系数g
units of N kg−1. This is equivalent to m s−2.
与r有关，地球非完美圆，故不同地方g不同
重力势能
gravitational potential is always negative.
This is because, as a mass is brought towards another mass, its g.p.e. decreases. Since g.p.e. is zero at infinity, it follows that, anywhere else, g.p.e. and potential are less than zero
势能差
术语
Field strength tells us about the force on unit mass at a point;
Potential tells us about potential energy of unit mass at a point
重力作用下的圆周运动
运动周期
18章 振动
oscillation
定义
An object oscillates when it moves back and forth repeatedly, on either side of some equilibrium position
分类
free
Every oscillator has a natural frequency of vibration，the frequency with which it vibrates freely after an initial disturbance.
Force
Many objects can be forced to vibrate，Their frequency is not the natural frequency
描述参数
振幅 amplitude
The maximum displacement from the equilibrium position is called the amplitude x0 of the oscillation
周期 Period
The period T is the time for one complete oscillation
频率 frequency
The frequency f is the number of oscillations per unit time
The frequency or period of a simple harmonic oscillator is independent of its amplitude.
角频率 angular frequency
相位 Phase
The term phase describes the point that an oscillating mass has reached within the complete cycle of an oscillation
simple harmonic motion (s.h.m.)
三个条件
a mass that oscillates
a position where the mass is in equilibrium
a restoring force that acts to return the mass to its equilibrium position; the restoring force F is directly proportional to the displacement x of the mass from its equilibrium position and is directed towards that point
描述式
位移
速度（速率speed）
（最大速度）
加速度
能量
The kinetic energy and potential energy of an oscillator vary periodically, but the total energy remains constant if the system is undamped
总能量
阻尼振动 Damped oscillations
Resistive forces remove energy from an oscillating system. This is known as damping. Damping causes the amplitude to decay with time.
例：汽车车架里的弹簧阻尼，防止频繁振动，提升舒适性
共振 resonance
Maximum amplitude is achieved when the driving frequency matches the natural frequency of oscillation
When an oscillating system is forced to vibrate close to its natural frequency, the amplitude of vibration increases rapidly. The amplitude is maximum when the forcing frequency matches the natural frequency of the system; this is resonance
三个特点
Its natural frequency is equal to the frequency of the driver
Its amplitude is maximum
It absorbs the greatest possible energy from the driver
阻尼与共振
Damping reduces the amplitude of resonant vibrations
Critical damping is the minimum amount of damping required to return an oscillator to its equilibrium position without oscillating
共振的危害与使用
problem 问题与危害
风与固有频率一致导致共振，桥梁倒塌
地震频率与建筑固有频率一致形成共振，建筑倒塌
useful case 使用
MRI 核磁共振
微波炉
微波频率与水分子固有频率相同，向水分子传递能量
19章 热学
change of state
solid
the particles are close together, tightly bonded to their neighbours, and vibrating about fixed positions
liquid
particles are close, bond to neighbours but change neighbours frequently, can slides each other freely
gas
the particles have broken free from their neighbours; they are widely separated and are free to move around within their container
hating ice sample
electrical potential energy of atoms is negative and increases as they get further apart
AB
temperature rise, kinetic energy is increasing, very little change in electrical potential energy
BC
melt at 0℃,modest increase in electrical potential energy
CD
kinetic energy is increasing, very little change in electrical potential energy
DE
boiling at 100℃,electrical potential energy increase greatly
temperature as a measure of the average kinetic energy of the molecules
Evaporation
When a liquid changes to a gas without boiling, we call this evaporation
This cooling of a liquid is a very important aspect of evaporation.
Internal energy
The internal energy of a system (such as the heated stone) is defined as the sum of the random distribution of kinetic and potential energies of its atoms or molecules.
First law of thermodynamics 热力学第一定律
increase in internal energy = energy supplied by heating + work done on the system
A positive value of ΔU means that the internal energy increases, a positive value of q means that heat is added to the system, and a positive value of W means that work is done on the system
a gas donging work
W = pΔV
Work done when the volume of a gas changes at constant pressure.
meaning of temperature
Thermal energy is transferred from a region of higher temperature to a region of lower temperature.
When two objects are at the same temperature, they are in thermal equilibrium
thermodynamic (Kelvin) scale
It is not possible to have a temperature lower than 0 K, 0K is know as absolute zero
absolute zero is the temperature at which all substances have the minimum internal energy. (The kinetic energy of the atoms or molecules is zero and their electrical potential energy is minimum.)
Thermodynamic temperatures do not depend on the property of any particular substance.
thermometers 测温计
A thermometer is any device that can be used to measure temperature
Each type of thermometer makes use of some physical property of a material that changes with temperature
---the resistance of an electrical resistor or thermistor
---the e.m.f. (voltage) produced by a thermocouple
---the colour of an electrically heated wire
---the volume of a fixed mass of gas at constant pressure
specific heat capacity (of the material)
The specific heat capacity of a substance is the energy required per unit mass of the substance to raise the temperature by 1 K (or 1 °C).
unit:J/(kg.K) or J/(kg.℃)
specific latent heat ( of a material)
Energy must be supplied to melt or boil a substance.
When a substance melts, this quantity is called the specific latent heat of fusion 融化热
for boiling, it is the specific latent heat of vaporisation 蒸发热
L is measured in J kg^−1
specific latent heat of fusion of water, 330 kJ kg^−1
specific latent heat of vaporisation of water, 2.26 MJ kg^−1
蒸发热比熔化热大得多
20章 理想气体 Ideal Gas
20.1 Fast molecules
standard temperature and pressure (STP, −0 °C and 100 kPa)
the average speed of the molecules is about 400 m s^−1
202. Pressue
The pressure on the inside of the box is a result of the forces exerted by the vast number of molecules in the box
20.3 measure gas
pressure
1 Pa = 1 N m^−2
temperature
T (K) = θ (°C) + 273.15
volume
m3.
mass
A mole of any substance (solid, liquid or gas) contains a standard number of particles (molecules or atoms). This number is known as the Avogadro constant, NA. The value for NA is 6.02 × 1023 mol−1.
20.4 Boyle's law
The pressure exerted by a fixed mass of gas is inversely proportional to its volume, provided the temperature of the gas remains constant.
pV = Constant
20.5 changing temperature
for a fixed mass of gas, apply to ideal gas
20.6 ideal gas equation
pV = nRT or pV = NkT
n is the amount (number of moles) of an ideal gas
N is the number of molecules
R = 8.31 J mol−1 K−1
k is the Boltzmann constant
20.7 modelling gas：the kinetic model
Its temperature indicates the average kinetic energy of its particles;
假设条件
1. Molecules move at random, colliding elastically with the walls.
2. The volume of the molecules is small compared to the volume of the container.
3.Therearenoforcesbetweenatomsinthegas.
4.Thetimeofeachcollisionissmallcomparedtothetimebetweencollisions
20.8 Temperature and molecular kinetic energy
We write the average value of c2 as <c2>
The root-mean-square speed
如果K氏温度变为2倍，<c>变为√2倍
21章 Uniform electric fields
21.1 电荷间力
同种电荷互相排斥，异种电荷互相吸引
21.2 电场 electric field
an electric field anywhere where an electric charge experiences a force
An electric field is a field of force
典型电场
方向：从正电到负电方向，代表了正电荷受力方向
强度：从线的稀疏程度可以展现
21.3 电场强度Electric field strength
The electric field strength at a point is defined as the force per unit charge exerted on a stationary positive charge at that point
单位
The strength of a uniform field
21.4 Force on a charge
电子在匀强电场里的运动（The parabolic path of a moving electron in a uniform electric field），类似于重力场的平抛运动
22章 Coulomb’s law库伦定律
22.2 Coulomb’s law
Coulomb’s law states that any two point charges exert an electrical force on each other that is proportional to the product of their charges and inversely proportional to the square of the distance between them.
22.3 Electric field strength for a radial field
22.4 Electric potential
Energy in a radial field
The potential changes according to an inverse law near a charged sphere
等势线
The electric field around a positive charge. The dashed equipotential lines are like the contour lines on a map; they are spaced at equal intervals of potential.
两个电电荷间电势能
两个点电荷间的两点间电势差
Field strength and potential gradient
23章 Capacitance电容
23.1Capacitors
Capacitors are used to store energy in electrical and electronic circuits
1 pF = 10^−12 F
1 nF = 10^−9 F
1 µF = 10^−6 F
23.2 Energy stored in a capacitor
23.3 Capacitors in parallel
23.4 Capacitors in series
23.7 Charge and discharge of capacitors
24章 Magnetic fields and electromagnetism
24.1 magnetic fields
The magnetic field lines come out of north poles and go into south poles 从N极指向S极
The direction of a field line at any point in the field shows the direction of the force that a ‘free’ magnetic north pole would experience at that point 方向代表了小磁针N极方向
The field is strongest where the field lines are closest together 疏密程度代表了磁场强度
实质：All magnetic fields are created by moving charges
电流产出的磁场方向
Two rules for determining the direction of a magnetic field, a inside a solenoid and b around a current-carrying wire
右手法则
螺线管
四指指向电流方向，大拇指指向磁场方向
通电导线
大拇指指向电流方向，四指指向磁场方向
24.2 Magnetic force
从磁场强的到磁场弱的地方产生电磁力
左手法则
磁力线穿过掌心，四指指向电流方向，则大拇指指向受力方向
24.3 Magnetic flux density 磁通密度
The unit for magnetic flux density is the tesla, T. It follows from the equation for B that 1 T = 1 N A−1 m−1
24.5 Currents crossing fields
不垂直，电流方向与磁力线夹角为q
电流方向与磁力线交接为q
24.6 Force between currents
电流方向：异向相斥，同向相吸
可以用磁吸线从密处向稀疏处有作用力解释
24.7 磁场、电场、重力场作用力比较
The force between two 1 kg masses 1 m apart = 6.7 × 10^−11 N
The force between two charges of 1 C placed 1 m apart = 9.0 × 10^-9 N
The force per metre on two wires carrying a current of 1 A placed 1 m apart = 2.0 × 10^−7 N
25章 Motion of charged particles
25.1 magnetic force
with the particle’s velocity at right angles to the field
F = BQv
力的方向服从左手法则
If the charged particle is moving at an angle θ to the magnetic field
25.2 Orbiting charged particles圆周运动
磁场作用力=向心力
r 正比于 v，m
r 反比与 B, Q
25.3 Electric and magnetic fields
A velocity selector – only particles with the correct velocity will emerge through the slit S.
25.4 The Hall effect
The Hall effect is the production of a potential difference across an electrical conductor when an external magnetic field is applied in a direction perpendicular to the current.
n is the number density of charge carriers
q is the charge of an individual charge carrier.
t is the thickness of the slice
26章 Electromagnetic induction电磁感应
26.2 Explaining electromagnetic induction
感应方向：右手法则
伸开右手，使拇指与其余四个手指垂直并且都与手掌在同一个平面内；让磁感线从掌心进人，并使拇指指向导线运动的方向，这时四指所指的方向就是感应电流的方向.如图所示.
垂直时
不垂直，B与平面法线夹角为q
当有N圈的线圈时
磁通量单位 weber (Wb)
1 Wb = 1 Tm2.
26.3 Faraday’s law of electromagnetic induction
The magnitude of the induced e.m.f. is directly proportional to the rate of change of magnetic flux linkage
26.4 Lenz’s law
Any induced e.m.f. will be established in a direction so as to produce effects that oppose the change that is producing it.
26.5
generator发电机
transformer
you can increase the induced e.m.f. at the secondary coil by increasing the number of turns of the secondary coil. 副线圈N多，增压变压器 Having fewerturns on the secondary will have the reverse effect. 副线圈N少，降压变压器
27章 Alternating currents 交流电
27.1
ω = 2πf
I = I0 sin ωt
V = V0 sin ωt
27.3 Power and alternating current
Root-mean-square (r.m.s.) values
等效直流电，可以提供等效的电能功率
计算电功率，采用r.m.s值计算
27.4 Rectification 整流
Half-wave rectification of a.c. requires a single diode.
Full-wave rectification of a.c. using a diode bridge.
A smoothing capacitor is connected across (in parallel with) the load resistor.
28章 Quantum physics 量子物理
28.1 wave or particle
光的波粒二象性
light travelled through spaceas a wave
28.2 Particulate nature of light
The photoelectric effect, and Einstein’s explanation of it, convinced physicists that light could behave as a stream of particles
h is called the Planck constant. h has an experimental value equal to 6.63 × 10^−34 J s.
eV 电子伏特用于原子物理，1 eV = 1.60 × 10^−19 J
低速情况下适用，接近于光速的高速不适用，因为m变大
28.3-4 The photoelectric effect Threshold frequency and wavelength
28.5 Photons have momentum
The tail of a comet is evidence that photons of sunlight have momentum
28.6 Line spectra
连续光谱经过衍射格栅被分离
不同元素有不同的特征光谱
连续光谱通过某元素气体，会某些光谱被吸收 d absorption line spectra
28.7 Explaining the origin of line spectra
The energy of the electron in the atom is said to be quantised.
28.8 Photon energies
28.9 The nature of light
This duality is referred to as the wave–particle duality of light
Light interacts with matter (e.g., electrons) as a particle – the photon. The evidence for this is provided by the photoelectric effect
Light propagates through space as a wave. The evidence for this comes from the diffraction and interference of light using slits.
28.10 Electron waves （Louis de Broglie提出）
证据：电子的衍射图
应用：电子显微镜，可以观察分子、原子以及原子核
电子的波粒二象性
An electron interacts with matter as a particle. The evidence for this is provided by Newtonian mechanics.
An electron travels through space as a wave. The evidence for this comes from the diffraction ofelectrons.
29 Nuclear physics 原子物理
29.1Balanced equations
In α decay, the nucleon number decreases by 4 and the proton number decreases by 2.
In β− decay, the nucleon number is unchanged and the proton number increases by 1
In β+ decay, the nucleon number is unchanged and the proton number decreases by 1
In gamma decay, there is no change in either nucleon number or proton number.
29.2 mass and energy
The total amount of mass and energy in a system is constant. There may be conversions from one to the other, but the total amount of ‘mass–energy’ remains constant.
Einstein's mass-energy equation
Einstein pointed out that his equation ΔE = Δmc2 applied to all energy changes, not just nuclear processes
原子物理使用的质量单位u ，1 u = 1.660 538 921(73) × 10^−27 kg
29.4 Binding energy and stability
The minimum energy needed to completely pull a nucleus apart into its separate nucleons is known as the binding energy of the nucleus
The greatest value of binding energy per nucleon is found for Fe（56） . This isotope of iron requires the most energy per nucleon to dismantle it into separate nucleons; hence iron-56 is the most stable isotope in nature. 铁最稳定，因此Fe56是地球上最稳定的同位素
Binding energy, fission and fusion
裂变 Fission is the process in which a massive nucleus splits to form two smaller fragments
聚变Fusion is the process by which two very light nuclei join together to form a heavier nucleus
29.5 Randomness and radioactive decay
radioactive decay is a random （随机的）, irregular phenomenon
Radioactive decay is both spontaneous（自发的） and random
the decay of a particular nucleus is not affected by the presence of other nuclei
the decay of nuclei cannot be affected by chemical reactions or external factors such as temperature and pressure 不受外界影响，包括温度和压力等
29.6 mathematics of radioactive decay
半衰期
30章 Medical Imaging 医疗影像
30.1 x-ray
X-rays have wavelengths in the range 10−8 m to 10^−13 m
与g射线相同，只是产生途径不同
x-ray来自于高速电子减速过程
g射线来自于核放射过程
x射线机原理图
30.2 原理
不同材料有不同的系数m
30.3 Improving X-ray images
to reduce as much as possible the patient’s exposure to harmful X-rays by image intensifiers
to improve the contrast of the image, using contrast media （I (53), Ba (56)碘或钡）
30.4 CT Computerised axial tomography
好处
They produce images that show three-dimensional relationships between different tissues.
They can distinguish tissues with quite similar densities (attenuation coefficients).
原理
360度旋转拍摄，同时可以轴向推进，从而形成3维的影像
30.5-7 Ultrasound scanning
原理
不同材料交界处会反射超声波，通过探测超声波的反射波成像
声阻抗 acoustic impedance
垂直入射，在交界处的反射与入射之比
30.8 正电子成像PET Positron Emission Tomography
基本原理
在PET中使用了几种不同的放射性示踪剂，例如一种基于葡萄糖的分子，上面附着着一种放射性核素，氟-18。这种物质被称为氟脱氧葡萄糖。氟-18核素通过发射一个β+粒子，一个正电子而衰变（正负电子泯灭发出光）。使用葡萄糖基示踪剂的优点是，它可以被不同的组织或器官以不同的速率吸收。癌细胞比周围的健康细胞代谢更活跃，因此它们以更高的速率吸收葡萄糖，从而以更高的速率发出辐射。然后，这将作为一个明亮的区域出现在屏幕上，允许医生识别疾病，并确定用于治疗该疾病的任何治疗方法的进展和有效性。PET扫描不仅用于癌症的检测，而且是调查血液流动、心脏病和脑损伤的诊断工具，它们也被用于调查阿尔茨海默病和其他形式的痴呆症。
31章 Astronomy and cosmology 天文与宇宙
31.1 Standard candles
luminosity of a star is defined as the total radiant energy emitted per unit time.（Power)
太阳 L⊙, is about 3.83 × 10^26 W.
In astronomy, a standard candle is an astronomical object of known luminosity.
两种 standard candles
Cepheid variable stars造父变星
By measuring the period,astronomers could determine the luminosity of the star
Type 1A supernovae Type1A超新星
The luminosity of the star at the time of the implosion is always the same
31.2 Luminosity and radiant flux intensity
e light year (ly). A light-year is the distance travelled by light in a vacuum in a time of one year. Therefore: 1 ly = speed of light in vacuum × one year in seconds 1ly=9.5*10^15m
The observed intensity is known as radiant flux intensity F
unit:W m^−2.
31.3 Stellar radii 星星半径
Wien’s displacement law
constant=2.9*10^-3mK
σ is 5.67 × 10^–8 W m^–2 K^–4.
31.4 The expanding Universe
The observed wavelengths of all spectral lines from distant galaxies are longer than the ones observed in the laboratory. This is known as redshift.
红移是通过观察吸收线发现的，不是直接看发光光谱
Hubble’s law
v = H0d
H is about 2.4 × 10^−18 s^−1.
Doppler redshift
Evidence of Big Bang
通过恒星的退移速度推算宇宙年龄（bingbang时间点）为约140亿年