Quantum Flashcards
Photoelectric effect
When light above a certain frequency is shone on a metal and electrons are released.
Photoelectric effect equation
Planck x frequency = work function + max kinetic energy of electrons
Are electromagnetic waves transverse or longitudinal?
Transverse
What phenomenon shows light acting as a particle?
The photoelectric effect
Threshold frequency
Minimum frequency of light needed to emit an electron
Energy of photon equation
Energy = planck x frequency
Energy = planck x speed of light over wavelength
Why does a photon need a minimum frequency to liberate an electron?
The energy of a photon is dependent on the frequency, the energy must succeed the work function in order for electron emission
If a photon had a higher frequency than the threshold frequency what would occur?
The electron will be liberated and the remaining energy is the kinetic energy of the electron
If light is incident on a metal and photoelectron emission does NOT occur, what is the effect of increasing intensity?
*There will be more photons incident to the metal per second
*However they still carry the same amount of energy
*This energy is not enough to liberate electrons
*No effect
Define the work function
The energy required by an electron to overcome the metallic bonding holding it to a metal
What is an electron volt?
The kinetic energy of an electron that has been accelerated from rest through a potential difference of 1V
How does a fluorescent tube work?
*High voltage applied across the mercury vapour accelerates fast moving free electrons which collide with mercury atoms
*Mercury electrons are excited and move back to ground state, emitting a UV photon
*The tube’s phosphorus coating absorbs the UV photons and its electrons excite. They then cascade down the energy levels and release visible light photons
What can be used as evidence for the discrete energy levels in atoms?
Line emission and absorption spectra as the lines appear at the discrete points which show where a light photon of specific frequency and wavelength has been absorbed or emitted, this shows electrons can only absorb an exact amount of energy to be excited to the next discrete energy level.
What is wave particle duality?
All particles have particle and wave like properties, waves have particle properties. E.G the photoelectric effect shows light acting as a particle and diffraction shows light as a wave.
De Broglie wavelength equation
wavelength = planck over momentum
