Lecture 1

Question 1

What is the equation for the speed of light in a vacuum?

Answer 1

c = speed of light
f = frequency
λ = wavelength

Question 2

What is the value of the speed of light in a vacuum?

Answer 2

2.9979 x 10⁸ m/s

Question 3

What is the equation for the energy of a photon?

Answer 3

E = energy
h = Planck’s constant
f = frequency
c = speed of light
λ = wavelength

Question 4

What is the equation for the kinetic energy of an electron?

Answer 4

E = kinetic energy
mₑ = mass of the electron
v = velocity

Question 5

What is the equation for the force on a charged particle in an electric field?

Answer 5

F = force
q = charge of particle
E = electric field (= potential difference/separation)

Question 6

What is the equation for the work done on a charged particle?

Answer 6

W = work done
q = charge of particle
V = potential difference

Question 7

What is the energy of a photon or charged particle measured in?

Answer 7

Electron volts, eV

Question 8

What is 1eV in J and what is the conversion factor?

Answer 8

1eV = 1.6 x 10⁻¹⁹ J

Joules to eV: ÷ 1.6 x 10⁻¹⁹
eV to Joules: x 1.6 x 10⁻¹⁹

Question 9

What is the conversion factor between the wavelength of a photon in nm and its energy in eV?

Answer 9

1238 eV nm

(divide this value by the wavelength in nm to get the energy or by the energy in eV to get the wavelength)

Question 10

What is the energy-mass equivalence equation?

Answer 10

E = energy
m = mass
c = speed of light

Question 11

What is the energy released if an electron’s rest mass is fully converted?

Answer 11

511 keV

Question 12

What is 1 atomic mass unit (amu) in kg and what is the conversion factor?

Answer 12

1 amu = 1.6605 x 10⁻²⁷ kg

kg to amu: ÷ 1.6605 x 10⁻²⁷
amu to kg: x 1.6605 x 10⁻²⁷

Question 13

What is the conversion energy of 1 amu (in eV)?

Answer 13

1 amu = 931 MeV

MeV to amu: ÷ 931
amu to MeV: x 931

Question 14

What is the equation for the relativistic kinetic energy of a particle?

Answer 14

E = kinetic energy
mₒ = rest mass of the electron
c = speed of light
v = velocity

Question 15

How do electrons orbit the nucleus according to the Bohr model?

Answer 15

They orbit in defined energy levels.

Question 16

What is the equation for the energy of the photon that is emitted when an electron moves between energy levels in an atom?

Answer 16

E = energy
h = Planck’s constant
c = speed of light
λ = wavelength
R = Rydberg’s constant = 1.0974 x 10⁷ m⁻¹
n₁, n₂ = energy levels

Question 17

What is Rydberg’s constant?

Answer 17

1.0974 x 10⁷ m⁻¹

Question 18

Describe the photoelectric effect

Answer 18

An incoming photon can collide with an atom and be absorbed if it has a high enough frequency. This results in the ejection of a photoelectron that has a kinetic energy determined by the difference between the energy of the incoming photon and the work function (ionisation potential).

Question 19

What is the equation for the energy of an emitted photoelectron in the photoelectric effect?

Answer 19

E = kinetic energy
h = Planck’s constant
c = speed of light
λ = wavelength
Φ = work function = ionisation potential

Question 20

When is radiation ionising?

Answer 20

When a photon or energetic particle has enough energy to eject an electron from its shell.

Question 21

What types of EM radiation is ionising?

Answer 21

• UV
• X-rays
• Gamma rays

Question 22

How can the ionisation potential for a particle be found?

Answer 22

Use the equation for the energy of an emitted photon when electrons move between energy levels but set the second energy level to infinity (to signify that the electron has been ejected). This is the value of the ionisation potential, hence, is the minimum energy required for a photon to eject an electron from that particle.