Particles - Quantum Phenomena (Module 3)

Question 1

What is the intensity of the incident radiation proportional to?

Answer 1

The number of electrons emitted per second is proportional to intensity of the incident radiation

Question 2

Define Threshold Frequency

Answer 2

The minimum frequency of light that can cause the photoelectric effect

Question 3

Define work function (work function energy)

Answer 3

The minimum amount of energy needed by an electron to escape the metal surface

Question 4

What is the energy of a photon equal to?

Answer 4

Energy of a photon=planck’s constant x frquency (E=hf)

Question 5

What does any excess energy become after there has been enough work function energy to release an electron?

Answer 5

Excess energy gained by the electron becomes its kinetic energy

Question 6

Explain the photoelectric effect

Answer 6

When light hits a metal surface, an electron on the surface absorbs a single photon and gains energy (equal to hf). The frequency must be greater than the threshold frequency of the metal and the energy gained by the single photon must be greater than the work function.

Question 7

What is stopping potential?

Answer 7

The minimum potential (positive charge) that needs to be applied to a metal plate to attract all the photoelectrons emitted from its surface back to the surface

Question 8

What is an electron volt?

Answer 8

It is a unit of energy equal to the work done when an electron is moved through a pd of 1V. The vaule of 1eV is 1.6x10^-19J

Question 9

Explain excitation

Answer 9

Excitation is the process in which an atom absorbs energy without becoming ionised due to an electron within the atom moving from an inner shell to an outer shell. Unit of energy required at each shell (usually) in eV

Question 10

Explain why and what happens when an electron de-excites

Answer 10

When an atom gets excited and the electrons move between shells, they leave gaps in the shell they moved from. Sooner or later, the gap is filled by another electron from an outer shell. When this happens, a photon is emitted

Question 11

Give an example of 2 ways to show that light has a wave-particle duality

Answer 11

Light can be proven to be a wave by showing how it diffracts, reflects, refracts etc.
Light can be proven to be a particle via the photoelectric effect and how the atoms in the metal absorb only one photon. You could also prove particle like nature by how light is deflected by a magnetic field