Electromagnetic forces acts on electrons-holds atoms together Strong Nuclear force acts on nucleons-holds nucleus together Weak Nuclear force acts on nucleons-radioactive decay Gravitational forces acts on all matter- holds planets together

Planck’s Black body radiation

A Black body wont reflect any light (or other electromagnetic radiation) When heated it will emit electromagnetic radiation (eg hot plate)

𝐄 = 𝐡𝐟 =𝐡𝐜

𝛌

𝟏𝐞𝐕 = 𝟏.𝟔 × 𝟏𝟎−𝟏𝟗𝐉

𝒆𝑽 = 1 𝑒𝑙𝑒𝑐𝑡𝑟𝑜𝑛 𝑣𝑜𝑙𝑡 = 1.6 × 10−19𝑱

𝐄 = 𝐏𝐡𝐨𝐭𝐨𝐧 energy Joules

𝐟 = frequency of the emitted radiation

𝐡 = planck constant = 𝟔.𝟔𝟑× 𝟏𝟎−𝟑𝟒𝑱s

𝐜 = 𝟑× 𝟏𝟎−𝟑𝟒𝒎/𝒔 𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑙𝑖𝑔𝑕𝑡

E ∝ f E = hf h =E

f=

J

𝐕 = 𝐟𝛌 𝐜 = 𝐟𝛌 𝐟 =𝐜

𝛌

∴ E =𝑕𝑐

𝜆

Black body radiation

Energy created by 𝑒 moving between defined energy

level within the atom (transitions).

Certain states of vibrations are more likely- hence the

peak in the frequency distribution curve

Atoms can only vibrate at a certain frequency

Light energy not given of continuesly but in small

energy packets called ‘Quanta’ or Photons

WAVE MODEL FAILS BECAUSE PREDICTS •Increasing Intensity should increase KE of e

•Photoelectric effect will occur for all frequencies but in fact there is a threshold frequency

Photo electric effect Lights can be particle & come in small packets called

photons

Short 𝜆 light or U.V on metal surface 𝑒 are ejected as

photocurrent

𝒆 bound to surface with binding energy called the

work function W

𝒆 only ejected if frequency of incident light exceeds the

MIN threshold frequency 𝐟𝟎 for that particular metal

f>F0

Using light with larger f increases the KE of ejected 𝑒

Once photocurrent is registered, increasing intensity

will increase photocurrent

Negative potential V is applied to collector plate (anode)

which repels the 𝑒 and when large enough to stop

photocurrent then this is stopping potential or cut-off

voltage 𝑽𝟎 & the current will flatten out to a maximum.

W= 𝐡𝐟𝟎

𝐊𝐄𝐌𝐀𝐗 = 𝐡𝐟 −𝐰 = 𝐡𝐟 − 𝐡𝐟𝟎 =𝟏

𝟐𝐦𝐯𝟐 = 𝐞𝐕𝟎

𝒆 = 𝒄𝒉𝒂𝒓𝒈𝒆 𝒐𝒇 𝟏 𝒆𝒍𝒆𝒄𝒕𝒓𝒐𝒏 𝟏.𝟔× 𝟏𝟎−𝟏𝟗

𝐞

𝐬=

𝐜𝐮𝐫𝐫𝐞𝐧𝐭 𝐈

𝟏.𝟔× 𝟏𝟎𝟏𝟗𝐂=𝐈𝐌𝐀𝐗𝐞

𝒉𝒇 = 𝑬 = 𝑃𝑕𝑜𝑡𝑜𝑛 𝐸𝑛𝑒𝑟𝑔𝑦 𝑱

𝑾 = 𝑤𝑜𝑟𝑘 𝑓𝑢𝑛𝑐𝑡𝑖𝑜𝑛(𝐽) = 𝑖𝑜𝑛𝑖𝑠𝑎𝑡𝑖𝑜𝑛 𝑒𝑛𝑒𝑟𝑔𝑦

𝑽𝒐 = 𝑠𝑡𝑜𝑝𝑝𝑖𝑛𝑔 𝑝𝑜𝑡𝑒𝑛𝑡𝑖𝑎𝑙 𝑽

𝐑 → 𝐎 → 𝐘 → 𝐆 → 𝐁 → 𝐈 → 𝐕 → 𝐔𝐕 → 𝐗𝐫𝐚𝐲

𝜆 = 700 × 10−9 → λ = 400 × 10−9

White light=𝟕𝟎𝟎+𝟒𝟎𝟎

𝟐= 𝟓𝟓𝟎× 𝟏𝟎−𝟗𝒎

Wavelengths decrease→ Refracts more→

critical angle decreases→ frequency increases→

Photon Momentum (the Compton effect)

𝐄 = 𝐦𝐜𝟐 = 𝐡𝐟

mc =hf

c

𝐦𝐜 = photon momentum = 𝐩

𝐩 =𝐡𝐟

𝐜=𝐡

𝛌=𝐄

𝐜 𝐰𝐡𝐞𝐫𝐞 𝐜 = 𝐟𝛌

WAVE PARTICLE DUALITY ALL PARTICLES BEHAVE AS WAVES

Debrogil wavelength

𝛌 =𝐡

𝐦𝐯=𝐡

𝐩

CONSERVATION OF MOMENTUM

m1u1 + m2u2 = m1v1 + m2v2

F = ∆ momentum (P)

time= N

CONSERVATION OF KINETIC ENERGY

½m1v21 + ½m2v

22 = ½m1u

21 + ½m2u

22

ELECTRON GUN

𝐪𝐞 × 𝐕 =𝐦𝐯𝟐

𝟐⟹ 𝐯 =

𝟐 × 𝐪𝐞 × 𝐕

𝐦

X-Ray Scattering- The Compton affect & light pressure

De Brogile-Davisson & Germer Apparatus

Electrons from filament F are accelerated by a

variable potential difference V. After scattering

from crystal C they are collected by detector D

Photoelectric apparatus

Ionisation -process of removing electron or more from a neutral

atom creating a pos+ charged atom. Ionisation energy=w

𝑨𝒍𝒑𝒉𝒂 𝑹𝒂𝒅𝒊𝒂𝒕𝒊𝒐𝒏 𝜶

Positively charged particles being emitted from the nucleus of radioactive atoms. Alpha Particles- collide with matter and slow down transferring their kinetic energy to the other molecules shaking many of them apart leaving a trail of pos & neg ions in their wake.

𝑩𝒆𝒕𝒂 𝑹𝒂𝒅𝒊𝒂𝒕𝒊𝒐𝒏 𝜷 Electrons being emmited from the nucleus of radioactive atoms Beta Particles- move at very high speeds. Smaller & more penetrating than alpha particles

𝑮𝒂𝒎𝒎𝒂 𝑹𝒂𝒅𝒊𝒂𝒕𝒊𝒐𝒏 𝜸 High energy electromagnetic rays/photons being emitted from the nucleus of an atom. Happens around other decay when the atom rearranges itself to be more stable.

Gamma Particles- Extremely small (10-ג-13

m) & most penetrating. (no charge)

Bohr model of atom Electron will only radiate energy in exact quanta. 𝑒 move inward to nucleus until

stable state is reached.

Nuclide-Name & symbol of a particular atomic species eg C or H etc Einstein said “Matter & Energy are not separate quantities

but are different forms of one another” 𝐄 = 𝐦𝐜𝟐

Thompsons Plum pudding model No good because tiny particles fired at atom and can pass thru

Isotopes have same nuber of protons but different number of neutrons to original element & will behave

similar More protons= bigger atom=helps stability because

seperates charges

Strong Nuclear Force (binding energy) only affects within

distance of 5 × 10−15

Adding protons does not increase the strong nuclear force

No stable nuclides have E>8

Proton + Electron = Neutron

𝐄 = 𝐡𝐟 = 𝐄𝐢 − 𝐄𝐟

𝐄𝐢 = Energy of higher orbital

𝐄𝐟 = Energy of lower orbital

The total energy E of the electron in such an orbit

(this can also be found on the diagram below)

En =E1

n2

En = nhf

𝐄𝟏 = 2.17 × 10−18 𝐉 𝑜𝑟 13.6𝒆𝒗

𝐄𝐧 = The energy of that nuber orbital 𝐉

𝐧 = number of the orbital where e is 𝐉

Radius of Hydrogen atom=5 × 10−11𝑚

Nucleus=1

10,000 size of whole atom

Mass of proton=mass of neutron

Nucleus=99% of mass of whole atom

Determine potential (accelerating portential) V(volts)

when an electron (or particle) is shot through single slit or double slit grating.

1. Determine 𝛌 wave length

SINGLE SLIT

w =2Lλ

d 𝛌 =

𝐰𝐝

𝟐𝐋

DOUBLE SLIT

w =Lλ

d 𝛌 =

𝐰𝐝

𝐋

𝐰 = width of central maximum 𝐝 = distance between slits 𝐋 = distance to screen

2. Use wavelength to determine momentum- hence find the velocity

λ =h

mv=

h

p 𝐯 =

𝐡

𝐦𝛌

3. Velocity determines potential difference (Volts)

W = qV =1

2mv2 𝐕 =

𝐦𝐯𝟐

𝟐𝐪

XZA

A=Mass Number of nucleons (protons & Neutrons)

Z=Atomic Number= Number of protons in nucleus

𝟏𝐀 =1

2mass of C6

12 = 𝟏.𝟔𝟔𝟎𝟔× 𝟏𝟎−𝟐𝟕𝐊𝐠

Mass of- Proton=1.007276 u

Neutron=1.008665 u

Electron=.000549 u

1u=931 MeV (binding energy)

Mass of constituents>actual mass

Transmutation (EG caused by ALPHA BOMBARDMENT)

Alpha Decay (ATOMS HEAVIER THAN URANIUM-238)

XZA → YZ−2

A−4 + He +24 energy (γ)

Beta Decay (ATOM HAS SURPLUS OF NEUTRONS)

XZA → YZ+1

A + e +−10 energy (γ)

Positron Decay (SURPLUS OF PROTONS)

XZA → YZ−1

A + e ++10 energy (γ)

Mass Defect represents mass that has been converted into

binding energy

𝐄𝐧𝐞𝐫𝐠𝐲 (𝛄) BINDING ENERGY (relates to fo)

E = (Mass− Actual Mass) × c2

Mass Defect=Mass-Actual Mass

Fission- Breaks apart

Fusion- Puts together

Tritium- 𝐻13

HALF LIFE

N

NO= (

1

2)n

logN

NO= n × log

1

2

n =time

time of half life=

t

t12

N = number of particles

NO = Initial number of particles

Mark Riley

markriley85@hotmail.com