H2 Phvsics (9745)

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Basic / primary / fundamentalquantities

Quantities that, by agreement, are treated as independent of any

other quantiiies.(mass Ikg], length lml, time [s], temperature IK], amount ofsubstance lmol], electric current [A], luminous intensity [cd])

Derived / secondary quantities Quantities obiained by simple combinarion of the basrc quantities.

One Newton (N = kg m s') Amount offorce acting on a mass of 1 kg causing a constantacceleration of 1m s2.

one Joule (J = kg m'zs_2) Amount ofwork done bya force of 1N when its poinl ofapplicationmoves through a distance of 1 m in the direction ofthe force.

lJncommon pretixes T (tera = 101':)

P (peta = 1O1s) f (femto = 1015)

a (atto = 1014)

One Mole The amount of substance that contains as many elementary entities(atoms, ions, molecules etc) as there are atoms in 12 g of C-12.

3t.?>

Scalar quantities Quantities that requires only magnitude to be fully described-

Vector quantities Quantities that requires both rragnitude and direction to be fullydescribed-

Relative velocity VA/B

(of A to a) (Vector addition gjves resultant;vector subtraction gives change in vector or relative value)

9zI

z3zo

=z

F'6t

-d

Reading Deiermination of a single value of an unknown quantity (raw valuegiven by any instnrments e.g. a calibrated value at a point on aruler).

J:ti""** t rr*- : i-a.*,rFinal result of the analysis of a series of readings e.g. the lglglbbetween 2 poinis is a measurement obtained by taking 2 !94!!g!at the 2 points and calculating the difference in the 2 readings.

Error (Uncertainty) t Ax The difference between a measurement and a true value.

Uncertd;ntres dre always e,(precsed to I s.l.

Systematic error Errors that occur according to a definite pattern, yielding consistentoverestimation (positive error) or undereslimation (negative error).

Errors that occur wiihout a definite pattern, with equal probabilities

of obtaining an overestimated (positive error) or an underestimated(negative error) measurement,The extent to which a measurement agrees with the true value,

Precision The extent to which a set of measurements done u nder the same

experimentalconditions agrees with one another{the spread ofthedata obtained).

E

Displacement The length travelled between the finaland the initial position ofabody in motion accompanied by a specific direction oftravel(denoted by a + or - sign or by an angle to a reference line).

Drlplacement per unrt lrrne. i-.r :,', b _' I

€hame in velocity per unittime;or-rate of change ofvelocity.

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(Law of inertia)A body at rest remains at rest and a body in uniform velocitycontinues its molion in a uniform velocity unless acled upon by an

external resultant force,

r,=E)I drJ

Newton's 2"" Law The rate ofchange ofmomentum of a body is directly proportional

to the magnitude of the applied force, and the change ofmomenium takes place in the direction of the applied force.

Newton's 3'o Law ln a mut!al interaction between 2 bodies, the force exerted by one

on another is equal in magnitude and opposite in direction to theforce exerted bV the other on it.

lnertia The property of a body which resists a change in its state of motion-

Mass is a measure of the inertia of a body (not the amount ofsubslance - mole).

Ate\e4

The product of the instantaneous velocity and the mass of a bodygives momentum.It is a measure of the reluciance of a system in changing its state ofmotion,

Elastic collision

(Perfectly elastic)

Collision in which bother linear momentum and total KE ofthesystem ;s conserved,

In a one-dimensional (head-on) collision, the relative velocity ofapproach before collision is equalto the relaiive velocity ofseparation aft er collision,When a moving body, A, collides head on elastically with a

stationary body, B, of identical mass, A comes to a stop and

moves off with the initial velocity of A.

B

lnelastic collision Collision in which the linear momentum is conserved but the totalKE ofthe system decreases.

Perfectly inelastic collision collision in which colliding bodies become a single combined body

moving with a common velocity after impact (coalesce).

lmpulse F At = area under the F-t graph = a momentum

lmpulsive force Force that acts for short durations / intervals.

9zI

=zzoF

=z

Hooke's Law(F = kx)

Within the elastic limits, the force applied

deformation, is directlv proportionalto itscontraction.

on an object, causing itslength ofexpansion or

Archimedes'Principle An object partially or fully immersed in fluid experiences an

upthrusi, which is equivalent in rnagnitude to the weight ofthe f uid

displaced, acting through the C.C. of the displaced fluid.

Moment (torque)(r = Fda)

The moment of a force is the product of the force and theperpendicular distance, d, between the axis of rotation and the line

of a.tion ofihe force-

Couple forces whose lines of action do

effect only (without translationnot2 equaland opposite parallel

coincide and produce turningmotion).

Translational equilibrium Ve.lor su/r of all the for Les a(tinB on ll'e objFCt / sysrem is rero.

Rotational equilibrium The sum of clockwise moments about any point in the system is

equal to the sum of anticlockwise moments about the same point inthe system.

3

E

=

Conservation of energy Energy may be transformed from one form to another but it cannotbe created or destroyed.i.e. the total energv in an isolated svstem is constant.

Work done

(w = Fdcoso)(w = JFdx)

Product ofthe force and the displacement ofan object in thedirection of the force.Work done can be negative (when € = 7r);

So can enerqv (gravitational potential energv).

work done per unit time.

dE

dx

The force on an object in a conservative field (region where energy

is conserved) is equalto the negative ofthe potentialener8ygradient.

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Anqular displacement The angle (in radian)turned in a specific direction.

Angular velocityd0 2n

= = 21tfdtT

The change in angular displacement per unit time.

l-:*..-z'lTanEentiallvelocity, v, along a circular path.

a=vo: :0, rf

Centripetal acceleration of a body in circular motion.

teng =vgt

Applicable for conical pendulum / aircraft system (horizontal circle)

in which 2 forces act on the circling body - the weight parallel to thevertical and another lifting force at an angle 0 to the vertical.

;

Newton's Law of Gravitation

F*j+Every particle of matter in the universe attracts every other particle

with a gravitational force that is directly proportionalto the product

of the masses of the particles and inversely proportional to thesouare ofthe distance between them.

GravitationalforceGMmF= , G = 6.7 x 10''- N m' kg '

r

The mutualattractive force a mass exert on another mass and vice

versa.

Gravitationalfield A region of space in which a mass experiences a force due io ihepresence of another mass,

Gravitational field strengthFGMmr'

The gravitationalfietd slrength at a point in a gravitationalfield is

defined as the gravitational force per unit mass acting on a !!!ql!test mass placed at that point.

9zI

:zgzoF=z

cravitational field stren8th q!lb!!a solid mass

8=kr

sphericalsolid mass

r, from the centre ofGravitational field strength at a point y{jl[!! a

(e.9. earth) increases linearly with its distance,

the solid (ear1h).

Gravitational potential energyGMmGPE=-

f

The GPE of a mass m at a point in the gravitational field is defined as

the work done to move the mass from infinity to the point by an

external agent without a chanse in its kinetic enerFV.

Gravitational potential

. GPE GM

tm

The gravitational potential at a point in ihe field is defined as thework done in moving a !!i! !0!!! from infinity to the point by an

external dgent without d (hanpe in its kinetic enerqv.

Keple/s Law For an orbiting body the square of its period is proportional to thecube of its radius.(Note: period is independent of mass of orbiiing body)

Geostationary orbit(r - a2oo0km)

The orbit of a satelliie directly above the equatorial line which has a

period that is exactly equal to the period of the rotation of the earth(" 24 hours).

Velocity of escape

KE+GGPE)=zero

v = \l2cl

The minimum initial velocity an object must attain in order to gain

the KE needed to move the objectfrom the surface of a mass 1e.9.planet)to infinity (free from the influence ofthe gravitationalfield

of the planet).

d(b d /GMld=- 1=--t

-'a' drl rl

Gravitational field strength is the negative ofthe gravitationalpotential gradient.

dGPE d / GMm\F=--=- |dr drt r lGravitationalforce is the negative ofthe gravitational potential

energy gradient.

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Simple Harmonic Motionx = xosinl,)t

v= vocosot, v = !rr)

A to and fro motion or periodic variation in which the acceleration is

directly proportional to the displacement from a fixed equilibriumposition (centre) and is always directed towards the fixed

equilibrium position, i-e. in the opposite direction to thedisplacement.

Resonance A phenomenon in which a system is forced jnto oscillation bY an

external driver frequency, responds with maximum amplitude,There is a maximum transfer ofenergy and it occurs at the naturalfrequency of the system-

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Basic assumption of kinetic theory

ofgases

(1) ldeal gases consist of large numbers of particles / molecules.

{2) For any one gas, all the molecules are of the same mass and size

(3)The molecules are always in random motion, continuoLlsly

strikine the walls ofthe vessels and colliding with each other.

ldealgaspV=nRT=Nkt

Obeys the equation pV = pRT exactly and satisfies all assumptions ofkinetictheory ofgases; F= no. of moles ofgas.

1rum(c')'3Vxs =

1p11= 1np1= 1py222

Average translation kinetic energy of a gas containing N molecules,

lh ERiV('')={,

EF

Thermalequilibrium When two bodies are in thermal contact and there is no net flow ofheat between them, they are said to be in thermal equilibrium.(same temperature; average KE of atoms are equa I but internal

energv LJ rnav varv)

Thermometric propertv A measurable physical property that increases or decreases

consistently with increasing temperature.(This property does not need to vary proportionally withtemperature.)

Triple point ofwater(273.16 Kj 0.01'C above ice po:nt)

Temperature at which 3 states of water - ice, water and watervapour are jn thermal equilibrium.

{Note: freezing point of water is 273.15 K)

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Heat capacitvThe amount of heat energy needed to raise a unit lemperature of an

obiect.

Specific heat capacity

Q= mcAo

The amount of heat energy needed to raise a Llnit temperature of a

unit mass.

specific latent heat of tusion

t,=gm

The amount of heat energy needed to change a unit mass ofthesubstance from solid phase to liquid phase without a change in

temperature.

Specific latent heat of vaporizationom

The amountofheat energy needed to change a unit mass ofthesubstance from liquid phase to Saseous phase wilhout a change in

temperature.

Latent energies

During phase change, Iatent energies are use to:(1) overcome molecLrlar attractions (break inter-molecular bonds),

(2) to expand against aimosphere.

Lu > Lr because vaporizalion involves breaking more intermolecular

bonds and expanding into a greater volume (greater work done

against atmosphere).

First Law of Thermodynamics

au=Q+w

Change in internal energy of a system (aU) is the sum of the work

done q! the system (W) and the heat :!-ppl.iCdlq the system (Q).

lnternal energy UThe sum ofthe potentialenergies and the kinetic energies oftherandom motion ofall the molecules in the system.

2 2

For idealgas,

6y = 6xg= 1Nk61= 1np61

Since there is no intermolecular interaction, potentialenergy among

atoms is zero and thus internal energy of an ideal gas depends solely

on KE of atoms which is proportional to the thermodynamictemperature ofthe gas.

Cyclic change

AU=0

Change which brings the state of the system throLrgh a series ofchanges and finally returning to its original state.

lsothermal transformation

AT = o lfor ideal eas.8U = 0l

Transformaiion which takes place at a constant temperature.

Adiabatic transformation

6Q=0

Transformation which takes place without any heat exchange withthe surroundings.

Area under the p-V graph

W= pAV(where p=constant)

Represents the work done associated with any process involving a

change in volume.

=

3

A wave in which the wavefront moves away fron the source thustransmitting energy from the source through the wave to the space

surrounding itAwave in which the directions ofoscillations ofthe particles is

perpendicular io the direction of propagation of the wave.

longitudinal wave A wave in which the directions ofoscillations ofthe particles isparallelto the direction ofpropagation ofthe wave.

Polarisation The process of restricting the oscillations of a transverse wave to a

specific pla ne.(Longitudinalwaves cannot be polarized as its direction ofoscillationcannot be restricted without affecting the propagation direction as

they are in the same direction.)

lntensity-1

The rate offlow ofenergy through cross sectional area

perpendicular to the direction of travel of the wave.

Principle of Superposition When 2 or more waves travel through a medium, the resllltantdisplacement at any point is the vector sum of the separate

displacemenis due to the individualwaves at that point.

Stationary waves The wave formed when 2 identicalwaves (same amplitude and

frequency)travelling with the same speed in opposite directionstowards one another superpose, resulting in regions of maxima(antinodes) and minima (nodes).

Diffraction A phenomenon where a wave spreads out and travel in all directionsafter passing through a narrow aperture.Superposition of 2 or more waves to Sive a resu tant wave ofamplitude given bv the principle of superposition.

Coherent sources Sources that produce waves with a constant phase difference at all

tirnes.The waves will have the same wavelength, frequency and speed.

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Steady current

t=Qt

The rate of flow of charges.

chargeQ=lt

The product ofcurrent and time.

l coulomb (c) The amountofcharge passing through a section ofthe circuitwherea steady current of 1 A flows for 1 s.

Potentialdifference

QI

The p.d. across an electrical device is defined as the amount ofelectrical energy converted to other forms of energy per unit chargepassing lhrough it.

1 volt {V)The p.d. across a device in a circuit in which 1J of eledrical energy is

converted into other forms of energy when 1 C of charge passes

through it.

Resistance

R=-I

The resistance of a conductor is defined as the Glig of the p.d.

across it to the current flowing through it.

1 ohm (o) The resistance of a conductor through which a current of 1 A flowswhen the p.d- across it is 1V.

Ohm's Law The current through a metallic conductor is directly proportionaltothe p.d. between its ends if the temperature and other physical

conditions stay the same.

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ElectromaBnetic force e.m.f .

a

The e.m.f. of a source is defined as the energy converted from otherforms into electrical energy per unit charge passing through it.

The e.m.f. of a source is defined as the electrical power supplied by

the source per unit current delivered by the source.

v'R

Work done per unit time.The rate ofdissipation/ conversion ofenergy.

Maximum PowerTheorem Maximum power is delivered to the load when the resistance of theload is equalto the internal resistance ofthe source,

Kirchhoff's First Law (Current Law) The algebraicsum ofthe currents at ajLrnction is zero (conservation

of charqe).

Potentialdivider

ln )^ lR l"

lf a p.d. is applied across several resistors in series, the p.d. across a

particular resistor is the product of the fraction of the resistance ofthat resistor to the overall resistance and the p.d. across the

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Root-mean-square valuet-

''' Jz

The r.m.s. value of an alternating current is its effective valuecorresponding to the value of a steady direct current, which willdissipate the same amount of heat in a given resistor ;n a given timeas the alternating current in the same circuit.

(P)=f'p at

T, t-v P_/Pl=t v =--L-+= rrJz 'lz z

P = lovosin'zot

Area under the P t graph is energy.

Mean power is the area under a P-t graph divided by time.Mean power in an alternating circuit is halfofthe maximum power ifthe A.C. is sinusoidal.

N"_V'=1,N, V. to

For idealtransformer where there is no

4, = P. (conservation of Energy)

heat loss,

Power loss in transmission

C".,=lv-=f

calculate power loss during a transmission using the formulaPb.=l':R whenever applicable.

tt P-lV - u

i<to be used,makesurFrhdtVRissubttiluledfortheR

tolal p.d. across the transmission cable i.e. across R and not the p.d.

ofthe supplv.

Half-wave rectif ication A single diode is connect in series with an A.C. supply, producing a

pulsating D.C. in the load (in series).

Half of the energy is wasted.

Full-wave rectif ication 4 diodes are connect with an A.C. sLrpply to produce a pulsating D.C.

in the load.No wastage in energy.Frequency of the pulsating output O.C. is twice that of original A.C.

I

coulomb's Law

'-lPThe force between 2 points is directly proportional to the product oftheir charges and inversely proportional to the square oftheirdistance aPart.

Electrostatic forceo o-

F = s:, €" = 8.85 x 10'"F m 'Ar.tor' "

The mutual force a charged particle exerts on another chargedparticle and vice versa,The force can be attractive (negative)or repulsive (positive) in

Elecrric f;eld A region of space in which a charged body experiences an

electrostatic force by virtue of its charge.

Electric {ield strengthFE=-q

The electric field strength at a point is defined as the electrostaticforce acting on a !!!A!! unit positive test charge placed at that point

in the electric field.

A radialfield by a point charge (non-uniform

field) follows the inverse square law:

-q-Qq4nenr' Afitof'

For uni{orm tield (e.g. field between parallelchargedplates:

VVoE=- F=xd

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oi

-

Electric field strength inside a

charged conductor

Electric fleld strength at any point inside a hollow charged conducto I'must be zero; a region of equipotential.

Electric potential energy lel3point charqe

u= Qq

4n€or

EPF of a charge q at a point in an electric field is defined as the work

done in moving the charge from infinity to the point in the electric

field by an external agent without a change in its kinetic energy.

Electric potential for a ooint

lbarce

v= Q4rr€or

Eleciric potentiaj at a point in an electric field is defined as the work

done in moving a unit positive test charge from infinity to the point

in the electric field by an exiernal agent without a change in itskinetic energy.

Electric potential inside a charged

conductor

Electric potential at all points inside a hol ow charRed conductor has

the same value as electric potential at the surface of the conductor.

ln general (i.e. for both point

charge and parallel charged plates)

dVE=--dxdU

dx

Electric field strength is the negative ofthe electric potentialenergygradient.Electric force is the negative of the electric potential energygradient.

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Magnetic field A region in space in which a current carrying conductor experiences

a magnetic force.

Magnetic field strength

Magnetic flux d€nsity (B)

Force experienced by a unit length of conductor, carrying a unitcurrent, placed perpendicular to the magnetic field.

FB=-lLsin0

(lrom F = al[sino dnd F = Bqvsino)

r Tesla (T) The strength ofthe magnetic field that results in a force of 1 N on 1

m of a conductor, carrying 1 A of current, placed perpendicular to

the magnetic field.

Magnetic Flux (O)

O=BrA

Magnetic flux through a plane surface is defined as the product of

the flux density (B) normalto the surface and the area (A) ofthe

Ma8netic {lux linkage (O = NC)

@ = NBrA

The magnetic flux linkage through a coil of N turns is defined as the

total flux through N turns of the coil where each turn experiences

the sarre maSneii. flux (0) throLlgh its ar ed.

l Weber {Wb) / The amounl of magneiic flux linking a coil of 1 turn that produces in

it an e.m-f. of 1V as it is reduced to zero at a uniform rate of 1 s

dO dNB AE=-=-

dtdt

When there is a change in magnetic flux through a circuit an e.m.f. is

set up in lhe circuit.The magnitude ofthe induced e.m.f. is proportionalto the rate ofchange offlux linkage.

[enz' Law

(the negative sign in equation ofFaraday's [aw)

dodt

The induced current always flow in a direction to oppose the chan8e

producing it.

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Photoelectric effect The phenomenon in which electrons are emitted from a solid

surface when it is irradiated with electromagnetic radiation.

Photon A'particle'ofelectromagnetic radiation, which carries a quantum ofenergy E that is related to its frequency f and the Planck constant h

by the equation:

e=nf=EI

7t6lof photoelectric emission

(a) ao-.Y%o'. ll .' f kutu .*i (C"-o^-

A1c,<;-o ,t*-^.e+\attr,,. t"1 tu--|>|"

l(1) no. of photoelectrons emitted per second depends on the

intensityot thF rncident rddiarion {rdteol arrivalof phoLon5 1""'""'J't42) Maximum velocity (KE) ofthe photoelectrons depends on thetype of photo emissive material irradiated and frequency of incidentphotons (and also the depth of the electrons before irradiation).

.(3)There will be no phoioemission if the frequency ofthe incident

radiation is below the threshold frequency fo ofthe material.

Work function (O) The minimum amount of energy needed by an electron for it to be

dislodged from a photo-emissive material.

hc

Threshold frequency {fo)The minimum frequency of the incident radiation that allowsphotoelectric emission from a 5!rface,

Threshold wavelength (l"o) The maximum wavelength ofthe incident radiation that willcausephotoelectric emission from a surface.

Einstein's photoelectric equation E **" o*- = 0-"a ""a.d*ia

+ KEmd (or em fred odoe etoD)

1.,i=4,*1.u.,,'

Stopping potential (V")

"Y =l,nu.",'

The polential of the anode of a photocell lhat is just enough to repel

all the approaching photoelectrons from the photocathode so thatlhe pffective Lullent through the pholo(ell is zero.

de Broglie wavelength A particle with momentum p is associated with a wavelength I give

by the de Broglie equation:

.hp

cround state (of an atom) The most stable state in which allthe electrons in the atom are in

their respective lowest enerqv states available.

Excited state (ofan atom) The unstable state in which one or more electrons in the atom have

transited to a higher energy level.

Excitation energy The amount of energy absorbed by an electron that transits fromthe lowest enerev level to a higher energy level.

lonisation energy The amount of energy absorbed by an electron that transits fromthe lowest energv levelto the highest energy ievel.

Transition to higher energy levels This phenomenon occurs when:(1) the electron collides with another electron with KE > excilation

energy, or

{2) the photon with hf = excitation energy is incident on the

Transition to lower energy levels A photon is released (emitted as electromagnetic radiation)withenergv corresponding to the AE between the levels.

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Bremstralung / Braking radiation Radiation of x-ray photons when high speed incident electrons are

slowed down / halted upon co lision with target metal.

Characteristic x-rays X ray photon of specific wavelengths are emitted when high speed

incident e ectrons knock out electrons frorn low energy orbits (near

the nuclei), and higher lying orbital electrons transit downwards tooccupy the vacancies created,Wavelengths of characteristic x-rays are dependent on energy levels

of atoms in target metal (independent of energy of incident

Heisenbere Uncertaintv Principle Position momentum uncertainty:

n*rro '-]L'4nEnergy'time uncertainty:

oro. r ]l4ft

Wave function (\y) A continuous function that can be used to describe a wave (orparticle). lt can extend into regions which are classically inaccessible.

l\,1'= ,rptitra"t of *rve function. lt gives the probability of finding

an electron at a point,

Scanning Tunneling Microscope

(srMl

A very high-resolution microscope that is used to obtain images ofconductive surfaces at atomic scale level, lt works on the basis ofelectron tunneling

Transmission coeff icient (T)

Reflection coefficient (R) R+T=1

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Population inversion Number of excited atoms is more than the number of ground state

Stimulated emission De-excitation of an excited atom by a perturbing photon ofmatching frequency.Resulting radiation has same phase, frequency, polarization and

direction of travel as the incident perturbing photon.

Valence Band The valence band is the highest range ofelectron energies where

electrons are normally present at absolute zero-

This is usually the uppermost occupied band.

Conduction Band Range of electron energy here is higher tha n that of the valence

band. Electrons are free to accelerate u nder the influence of an

applied electric field and thus constitute an electric current.This is usually the lowest unoccupied band.

n-type semiconductor Semiconductors which are doped with group 5 impurity atoms (e.9.

phosphorus, arsenic).Maioritv carriers in n tVpe semiconductor are electrons.

p-type semiconductor Semiconductors which are doped with group 3 impurity atoms (e.9.

boron, aluminium, gallium).Majoritv carriers in p type semiconductor are holes.

p-n junction as rectifier A p-n junction allows electric charges to flow in one direction, butnot in the opposite direction.When connected in a circuit with alternating e.m.f., it acts as a

rectifier to restrict current flow every half cycle (when it is in reverse

bias).

Depletion layer A layerformed at thejunction where the p-type and n typesemiconductors are in contact. lt is void of mobile charge carriers,

hence acts like a laver of insulation.

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Rutherford c.-scatterinB

experiment

lnference from the experiment:(1) Majority ofthe c. particles pass through undeflected

) an atom is largelY emPtY sPace,

(2) Some c(-particles are defiected to a large angle

+ there exist a positively charged body that is small but massive

enough to provide a magnitude of e ectrostatic force that can

repel the oncoming cL-particle to such a great extent.

Conclusion of Rutherford o-

scatterinB experiment

An atom has most of its mass and all

concentrated in a very small volumeElectrons are spread out around thelarge volume (= 10

to m).

its positive chargein its nucleus (= 101r m).

nucleus and occupy a much

lmportent rationale fortheexperimentalsetup

(1) Vacuum: air molecules caLrse deflection of cl'-particles. ln a

vacLrum, it can thus be conclusive that deflection of cl particles is

entirely due to its interaction with gold atoms.(2) Narrow parallel beam oI ct-particles: ensures that there is littledivergence in the deflected beam so as to facilitate measurement ofangles and to increase the precision,

(3) Thin gold foil is used: to maximize the probability that any

interactions causing the deflection is between a single o. particle and

a sinele eold atom.Number of protons in an atom (proton number).

Nucleon number Total number of protons and neutrons in an atom (mass number),

lsotopes Atoms that have the same number of protons but different number

Unified atomic mass unit ('r)

1u=1.66x10'z?kg

,1

- of the mass of a carbon-12 atom

1)'n1u is approximately the mass of 1 nucleon.ruc'z = 931 MeV

Einstein's energy equation E is the energy equivalence of mass m, and c is the constant speed

of light.Gain in energy is reflected as an increase in mass; loss of energy is

reflected as a decrease in mass.

Bindinc energv (BE) The amount of energy required to completely separate a nucleus

into its constituent nucleons.

Mass detect (Am) The difference between the mass of a nucleus and the total mass oftls qeparaie individJdl (on\lrluenr nucleon5.

Nuclear fusion The process where 2 small nLrclei fuse to form a larger nucleus wth a

release of energv.

Nuclear fission The process where a large nucleus breaks up into smaller nuclei (of

similar sizes)with a release ofenergv.The difference between the masses ofthe reactants in a nuclear

reaction and the masses ofthe products.

Energy released 2 ways to calculate:(1) Energy released(2) Energy released

1m,.,*""," - m0,"0,.,)c'BEp-a"o' BE'"*"*,

Binding energy per nucleon An indication ofstability-the largerihe BE/nucleon ofa nuclide,

the more stable the nuclide is.

Fe 56 is the most stable nuclide with the highest BE/nucleon {= 9.0MeV).

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Radioactive decay The process through which unstable nuclides eventually form stable

nuclides by the emission of subatomic particles (c{. or 0 particles) orT

Alpha particle I tt"Helium nucleus with charge +2e and mass 4 u.

Beta particle reElectron produced in the nucleus by the conversion of 1 neutron to a

proton and an electron. The proton remains in the nucleus while the

electron is ejected as the P particle.

Activity (A)

e=!!=rNdt

The rate at which radioactive nuclei are disintegrating within a

radioactive sample-(The number of radioactive nuclides that decay in a unii time)

Decay constant (l)" ln2

tt

The probability that an individual radioactive nucleus will decay in

Half life

('r)The time taken for half the total number of radioactive atoms in a

substance to decay.

Decay law

x =Xoe-r'Xo is the initial value o{ x at t = 0

ladioactive substance decays exponentially with iime.( can be:

1)Activity (A)

2)Count rate (C)

3) Number of radioactive nuclei (N)

4)Mass (m)

5) No. of mole (n)