Quantum Physics Flashcards
What is the “Photoelectric effect”?
when photons of sufficient energy are absorbed by electrons on the surface of a metal.
What is the equation for the kinetic energy left when an electron has escaped the metal?
EKmax= hf - work function
How many joules is one electron volt?
1eV=1.6x10^-19
What is the equation for kinetic energy?
Ek= 1/2mv^2
Explain the fluorescent tube practical.
A tube filled with mercury vapour with a phosphor coating with an anode and cathode at either end is supplied with a voltage, then the free electrons from the cathode collide with the mercury atoms transferring photons of energy exciting them. However, electrons are unstable after excitation and de excite after causing photons of the UV range to be emitted, then these excite the electrons in the phosphor coating and they also de excite after time and emit photons of visible light.
What does the photoelectric effect tell us about waves?
That waves can have a particle like nature
What is the de broglies wavelength?
lambda = plancks constant/momentum
What is the equation for stopping potential?
1/2mv^2=eVstop
What is threshold frequency?
The minimum frequency required for the electrons on a atoms metal to become photoelectric. This is because electrons need energy to excite to higher energy levels and have enough kinetic energy to leave the metal. Since E=hf (energy = frequency x plancks constant) energy is proportional to the frequency so by increasing the frequency you will also increase the energy.
What happens when you increase the intensity of a frequency?
The rate of photons being emitted increases.
What is one volt in electron volts?
one
What is the leyman series and what type of energy does it emit?
From any energy level to a lower energy (n = 1) level and it emits ultraviolet
What is the balmer series and what type of energy does it emit?
From any level above to the 2nd energy level and it emits visible light
What is the paschen series and what type of energy does it emit?
From any energy level above to the 3rd energy level and it emits infared
What do emission spectra show us?
The different wavelengths of photons when the atom is excited and eventually de excites, different elements have different emission spectra
