Modern Physics - Formula - Level 3 Flashcards
Energy
Symbol - E
Units - Joules (J)
Planck’s constant (6.63 x 10^-34)
Symbol - h
Units - Joule seconds (Js)
Frequency
Symbol - f
Units - Hertz (Hz)
or Seconds inverse (s^-1)
Work function
Symbol - Φ
Units - Joules (J)
Kinetic energy of an electron
Symbol - Ek
Units - Joules (J)
Charge of an electron (1.6 x 10^-19)
Symbol - e
Units - Coulomb (C)
Velocity of electron
Symbol - v
Units - Metres per second (ms^-1)
Mass
Symbol - m
Units - Kilograms (kg)
Rydberg constant
Symbol - R
Units - Meters inverse (m^-1)
Wavelength
Symbol - λ
Units - Meters (m)
Speed of light (velocity of radiation) (3 x 10^8)
Symbol - C
Units - Meters per second (ms^-1)
Energy value for a given energy level (n)
Symbol - En
Energy level number (1, 2, 3 ,…)
Symbol - n
Final energy level (first in equation)
Symbol - S
Inital energy level (second in equation)
Symbol - L
Equation for energy of a photon (from frequency)
Epho = hf
Where,
f is the frequency of the incident light
Equation for energy of a photon, when given the wavelength
Epho = hC/λ
Where,
λ is the wavelength of the radiation
What is the velocity of radiation equal to?
C = λf
Equation for photoelectric effect
Epho = Φ + Ek max
Where,
Epho is the energy present in the incident photon
Φ is the work function of the metal surface
Ek max is the maximum kinetic energy of the ejected photoelectron
Equation for threshold frequency
hfo = Φ
Where,
fo is the threshold frequency
Φ is the work function of the metal
Equation for kinetic energy and electrical potential energy
hf = hfo + 1/2 me ve^2
Where,
hf is the energy present in the incident photon
hfo is threshold frequency
1/2 me ve^2 is the kinetic energy of the electron
hf = hfo + Ve
Where,
hf is the energy present in the incident photon
hfo is threshold frequency (work function)
Ve is the electrical potential energy
(hfo + Ve = hfo + 1/2 me ve^2)
Converting from nano and micrometers to meters
Nano x 10^-9
(Mew) Micro x 10^-6
Converting from volts or joules to electronvolts
(Volts or joules) / (1.6 x 10^-19)
Converting from Megahertz to hertz
Megahertz x 10^6
Calculate the maximum wavelength when given the work function
Wavelength is indirectly proportional to frequency
(Max wavelength = Min frequency)
- Calculate the threshold frequency (Min frequency)
hfo = Φ - Calculate the wavelength (Max wavelength)
λ = C/fo
Equation for cutoff voltage from frequency and energy
Vo = (hf - hfo)/e
Where,
Vo is the cutoff voltage
hf is the energy present in the incident photon
hfo is the work function
Equation for kinetic energy
Ek = hf - Φ
Where,
Ek is the amount of kinetic energy that an
electron can have when it is ejected from the
metal after being hit with a photon of light of
frequency f (Hz).
hf is the energy present in the incident photon
Φ is the work function (threshold frequency)
Equation for cutoff voltage from kinetic energy
eVo = Ek
Where,
Vo is the cutoff voltage
Equation for energy of an electron in each level
E = -Rch/n^2
Where,
The negative sign indicates that when an atom is formed, energy is released when an electron is brought to an energy level from infinity where energy is zero.
Equation for mass deficit
△m = mr - mp
Where,
mr is the mass of the reactants
mp is the mass of the products
Equation for change energy from mass deficit
E = △mC^2
Where,
E is the change in energy
△m is the mass deficit
C is the velocity of the radiation (squared)
Equation for the current number of radioactive nuclei
N = No(1/2)^n
Where,
No is the original number of radioactive nuclei
N is the current number of radioactive nuclei
n is the number of half-lives
Calculate the frequency/wavelength of the radiation emitted by an electron jumping from one level to another
- Calculate energy difference
△E = Rch(1/na^2 - 1/nb^2)
Where,
E is the energy difference
nb is the higher energy level number
na is the lower energy level number
- Calculate frequency
E = hf - Calculate wavelength
λ = C/f
Equation for Lyman series
1/λ = R(1/1^2 - 1/n^2)
Where, n is the higher energy level number
Equation for Balmer series
1/λ = R(1/2^2 - 1/n^2)
Where, n is the higher energy level number
Equation for Paschen
1/λ = R(1/3^2 - 1/n^2)
Where, n is the higher energy level number
Equation for binding energy of nucleus
E = Rch/n^2
Where,
E is the binding energy
n is the energy level number which the electron has been removed from
Calculate the binding energy of an element per nucleon given unit u
- Write equation of element (either fission or fusion)
- Number of protons is atomic number
- Number of neutrons is mass number - atomic number - Calculate the total mass of the nucleons (mass number)
- Calculate the total mass of the element
- Subtract one mass value from the other to calculate the difference (Mass deficit)
- Convert mass deficit from units u, to kg
- Calculate the binding energy using E = mc^2
- Divide energy value by the number of nucleons in the particle
Converting from daltons (u) to kilograms
Daltons x (2.66054 x 10^-27)
Unit of radioactivity - Curie
Symbol - Ci
Units - Decays per second (1 Ci = 3.7 x 10^10)
Unit of radioactivity - Becquerel
Symbol - Bq
Units - Decays per second
(1 Bq = 1 decay per second)
- A becquerel is the rate of disintegration of a radioactive subastance
Converting from megaelectron volts (MeV) to joules
MeV x (1.6022 x 10^-13)
Converting from megajojules (MJ) to joules
MJ x (10^6)
Equation for the number of half-lives
n = t/T1/2
Where,
n is the number of half-lives
t is the total time
T1/2 is the time for one half-life
Equation for binding energy of nucleus per nucleon
Binding Energy per Nucleon = Total Binding Energy of the Nucleus / Number of Nucleons in Nucleus
