3.5 Modern Physics Flashcards
explain mass deficit
nucleons in product nuclei have lower energy than nucleons in reactant nuclei, energy is released. As mass includes energy, a reduction of energy means a reduction of mass.
how can mass deficit be justified
through the E=mc^2 equation. if energy decreases, mass decreases.
binding energy definition
The binding energy of a nucleus is the work done to overcome the nuclear forces and separate the nucleus into its nucleons. energy needed to ‘split the atom’.
E=mc^2
equation for binding energy per nucleon
= total binding energy/number of nucleons
why is there a decrease of mass after nuclear fusion.
individual nucleons have higher mass than when they are together in a nucleus. Because of the release of energy (bonds forming)
definition of photoelectric effect
the PE effect occurs when light is shone onto a metal surface and causes electrons to be ejected.
*a photoelectric cell can cause a small current
brighter light used (photoelectric effect)
MORE electrons emitted, Ek did not change
Dim light used (photoelectric effect)
electrons still emitted instantly, fewer
Frequency of light changed (photoelectric effect)
the higher the frequency, the greater the energy of the electrons emitted. SAME amount
converting joules -> eV
divide by charge of electron
how to find work function on the graph
y intercept
Ek = h f o (work function)
gradient of graph is equal to?
Plancks constant, h, 6.63x10^-34
What do the lines in the emission spectrum represent?
The energy levels of the electrons
to see emission spectrum, needs:
hydrogen discharge tube
to see absorption spectrum, need:
white light shone through cold hydrogen gas
