AS2 2.5 Quantum Physics Flashcards
What is a photon?
A photon is an indivisible packet of electromagnetic energy.
What did Einstein theorise about light?
Light is made up of photons
What does the energy of a photon depend on?
The frequency of the photon, NOT the intensity
What is photon energy proportional to?
Light energy
What is the equation for energy per photon?
E = hf
E = energy per photon (J)
f = frequency of light (Hz)
h = Plank’s constant (6.63 x 10^-34) (Js)
what is the equation for frequency? (Quantum Physics)?
f = V/ lamda
f = frequency (Hz)
V = speed of light (3 x 10^8) (m/s)
lamda = wavelength (m)
What is an electron volt and what is it equal to in joules?
It is another way of writing energy
1 electron volt = 1.6 x 10^-19 Joules
What observations can’t be explained using the energy of light?
- Emission of electrons from metal surface does NOT take place if the frequency of the EM radiation is below the threshold frequency?
- If the frequency is < threshold frequency, no matter how intense the radiation, no emissions will take place
- photoemission occurs without delay (provided f > threshold frequency
What is the photoelectric effect?
When light is incident on a metal surface, an electron volt at the surface absorbs a single photon from the incident light , and therefore gains energy equal to hf, where hf is the energy of a light photo
When can an electron leave the metal surface in the photoelectric effect?
An electron can leave the metal surface if the energy gained from a single photon exceeds the work function of the metal
What is the work function?
The minimum energy a photon must have to cause the emission of electrons?
What is the threshold frequency?
The minimum frequency a photon must have to cause the emission of electrons?
What is the equation for the energy of a photon?
E(photon) = work function + E(kinetic)
