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
Planckโs Black body radiation
A Black body wont reflect any light (or other electromagnetic radiation) When heated it will emit electromagnetic radiation (eg hot plate)
๐ = ๐ก๐ =๐ก๐
๐
๐๐๐ = ๐.๐ ร ๐๐โ๐๐๐
๐๐ฝ = 1 ๐๐๐๐๐ก๐๐๐ ๐ฃ๐๐๐ก = 1.6 ร 10โ19๐ฑ
๐ = ๐๐ก๐จ๐ญ๐จ๐ง energy Joules
๐ = frequency of the emitted radiation
๐ก = planck constant = ๐.๐๐ร ๐๐โ๐๐๐ฑs
๐ = ๐ร ๐๐โ๐๐๐/๐ ๐ ๐๐๐๐ ๐๐ ๐๐๐๐๐ก
E โ f E = hf h =E
f=
J
๐ = ๐๐ ๐ = ๐๐ ๐ =๐
๐
โด E =๐๐
๐
Black body radiation
Energy created by ๐ 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 โQuantaโ or Photons
WAVE MODEL FAILS BECAUSE PREDICTS โขIncreasing Intensity should increase KE of e
โขPhotoelectric 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 ๐ light or U.V on metal surface ๐ are ejected as
photocurrent
๐ bound to surface with binding energy called the
work function W
๐ only ejected if frequency of incident light exceeds the
MIN threshold frequency ๐๐ for that particular metal
f>F0
Using light with larger f increases the KE of ejected ๐
Once photocurrent is registered, increasing intensity
will increase photocurrent
Negative potential V is applied to collector plate (anode)
which repels the ๐ and when large enough to stop
photocurrent then this is stopping potential or cut-off
voltage ๐ฝ๐ & the current will flatten out to a maximum.
W= ๐ก๐๐
๐๐๐๐๐ = ๐ก๐ โ๐ฐ = ๐ก๐ โ ๐ก๐๐ =๐
๐๐ฆ๐ฏ๐ = ๐๐๐
๐ = ๐๐๐๐๐๐ ๐๐ ๐ ๐๐๐๐๐๐๐๐ ๐.๐ร ๐๐โ๐๐
๐
๐ฌ=
๐๐ฎ๐ซ๐ซ๐๐ง๐ญ ๐
๐.๐ร ๐๐๐๐๐=๐๐๐๐๐
๐๐ = ๐ฌ = ๐๐๐๐ก๐๐ ๐ธ๐๐๐๐๐ฆ ๐ฑ
๐พ = ๐ค๐๐๐ ๐๐ข๐๐๐ก๐๐๐(๐ฝ) = ๐๐๐๐๐ ๐๐ก๐๐๐ ๐๐๐๐๐๐ฆ
๐ฝ๐ = ๐ ๐ก๐๐๐๐๐๐ ๐๐๐ก๐๐๐ก๐๐๐ ๐ฝ
๐ โ ๐ โ ๐ โ ๐ โ ๐ โ ๐ โ ๐ โ ๐๐ โ ๐๐ซ๐๐ฒ
๐ = 700 ร 10โ9 โ ฮป = 400 ร 10โ9
White light=๐๐๐+๐๐๐
๐= ๐๐๐ร ๐๐โ๐๐
Wavelengths decreaseโ Refracts moreโ
critical angle decreasesโ frequency increasesโ
Photon Momentum (the Compton effect)
๐ = ๐ฆ๐๐ = ๐ก๐
mc =hf
c
๐ฆ๐ = photon momentum = ๐ฉ
๐ฉ =๐ก๐
๐=๐ก
๐=๐
๐ ๐ฐ๐ก๐๐ซ๐ ๐ = ๐๐
WAVE PARTICLE DUALITY ALL PARTICLES BEHAVE AS WAVES
Debrogil wavelength
๐ =๐ก
๐ฆ๐ฏ=๐ก
๐ฉ
CONSERVATION OF MOMENTUM
m1u1 + m2u2 = m1v1 + m2v2
F = โ momentum (P)
time= N
CONSERVATION OF KINETIC ENERGY
ยฝm1v21 + ยฝm2v
22 = ยฝm1u
21 + ยฝm2u
22
ELECTRON GUN
๐ช๐ ร ๐ =๐ฆ๐ฏ๐
๐โน ๐ฏ =
๐ ร ๐ช๐ ร ๐
๐ฆ
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
๐จ๐๐๐๐ ๐น๐๐ ๐๐๐๐๐๐ ๐ถ
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.
๐ฉ๐๐๐ ๐น๐๐ ๐๐๐๐๐๐ ๐ท Electrons being emmited from the nucleus of radioactive atoms Beta Particles- move at very high speeds. Smaller & more penetrating than alpha particles
๐ฎ๐๐๐๐ ๐น๐๐ ๐๐๐๐๐๐ ๐ธ 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-ื-13
m) & most penetrating. (no charge)
Bohr model of atom Electron will only radiate energy in exact quanta. ๐ move inward to nucleus until
stable state is reached.
Nuclide-Name & symbol of a particular atomic species eg C or H etc Einstein said โMatter & Energy are not separate quantities
but are different forms of one anotherโ ๐ = ๐ฆ๐๐
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 ร 10โ15
Adding protons does not increase the strong nuclear force
No stable nuclides have E>8
Proton + Electron = Neutron
๐ = ๐ก๐ = ๐๐ข โ ๐๐
๐๐ข = Energy of higher orbital
๐๐ = 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
๐๐ = 2.17 ร 10โ18 ๐ ๐๐ 13.6๐๐
๐๐ง = The energy of that nuber orbital ๐
๐ง = number of the orbital where e is ๐
Radius of Hydrogen atom=5 ร 10โ11๐
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 ๐ wave length
SINGLE SLIT
w =2Lฮป
d ๐ =
๐ฐ๐
๐๐
DOUBLE SLIT
w =Lฮป
d ๐ =
๐ฐ๐
๐
๐ฐ = width of central maximum ๐ = distance between slits ๐ = distance to screen
2. Use wavelength to determine momentum- hence find the velocity
ฮป =h
mv=
h
p ๐ฏ =
๐ก
๐ฆ๐
3. Velocity determines potential difference (Volts)
W = qV =1
2mv2 ๐ =
๐ฆ๐ฏ๐
๐๐ช
XZA
A=Mass Number of nucleons (protons & Neutrons)
Z=Atomic Number= Number of protons in nucleus
๐๐ =1
2mass of C6
12 = ๐.๐๐๐๐ร ๐๐โ๐๐๐๐
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 โ YZโ2
Aโ4 + He +24 energy (ฮณ)
Beta Decay (ATOM HAS SURPLUS OF NEUTRONS)
XZA โ YZ+1
A + e +โ10 energy (ฮณ)
Positron Decay (SURPLUS OF PROTONS)
XZA โ YZโ1
A + e ++10 energy (ฮณ)
Mass Defect represents mass that has been converted into
binding energy
๐๐ง๐๐ซ๐ ๐ฒ (๐) BINDING ENERGY (relates to fo)
E = (Massโ Actual Mass) ร c2
Mass Defect=Mass-Actual Mass
Fission- Breaks apart
Fusion- Puts together
Tritium- ๐ป13
HALF LIFE
N
NO= (
1
2)n
logN
NO= n ร log
1
2
n =time
time of half life=
t
t12
N = number of particles
NO = Initial number of particles
Mark Riley