2.4 - The Photoelectric Effect Flashcards
What is the definition of an electron volt?
A unit commonly used to express very small energies (specifically quantum energies as they tend to be below 1 Joule).
What is an electron volt?
Ev = 1.6 x 10⁻¹⁹ J
What is the relation from Ev to kinetic energy?
When an electron accelerates from rest, an electron volt is equal to the kinetic energy gained.
What is the photoelectric effect?
A phenomena in which electrons are emitted from the surface of a metal upon the absorption of electromagnetic radiation.
What are photoelectrons?
Electrons removed from a metal (with high frequency light).
What is the 2 step process of the photoelectric effect?
1) Free electrons on the surface of the metal absorb energy from the light.
2) If an electron absorbs enough energy, the bonds holding it to the metal break and the electron is released.
What is threshold Frequency?
The minimum frequency of incident electromagnetic radiation required to remove a photoelectron from the surface of a metal.
What is the work function? (Φ)
The minimum energy required to release a photoelectron from the surface of a metal.
How many photons do electrons absorb?
One.
What is stopping potential defined as?
The voltage (potential) difference required to stop electrons from moving between plates and creating a current in the photoelectric experiment.
What changes the value of the work function and threshold frequency?
The type of metal which the electrons are being emitted from.
What is the stopping difference equation?
Ekmax = eVs
e = charge of electron
Vs = stopping potential in V
What is the work done equation?
Work done = p.d x charge
How do you work out the energy of an incident photon?
Work function + the max kinetic energy of the photoelectron
What is the equation for the energy of a photon?
E = hf
E = hc/f
h = Plank’s constant (6.63E-34 Js)
c = Speed of light (3E8 ms^⁻¹)
f = frequency (Hz)
