3D.2 Flashcards
what are photoelectrons
they are electrons released from the surface of a metal due to be exposed to electromagnetic radiation
what is the work function
the minimum amount of energy needed for an electron at the surface of a metal to leave the metal
amplitude for light means
brightness
can any photoelectrons be released from shining a red light and why
no, because it is below the threshold frequency
what is the threshold frequency
it is the minimum frequency of electromagnetic radiation that can cause the emission of photoelectrons from the surface of a metal
what is the photoelectric effect equation
hf = 1/2mv^2(max) + work function
what is the stopping voltage
it is the minimum amount of voltage required to reduce the photoelectric current to zero. with illuminated with a particle frequency
how do we test for plank constant using a photoelectric cell
in a vacuum place the metal on an anode of a cell with a gap to a cathode, shine a light would known frequency at the anode to get electrons to be released starting a current, then you can vary the pd across the photoelectric cell using a variable cell, keep increasing the voltage until the photoelectric cell becomes positive stops emitting electrons, and starts to attach the electrons back to its self, the voltage that makes the Photoelectric cell positive is called the stopping voltage we can use that value to find the maximum kinetic energy, then we can vary the frequency of light and record the stopping voltage for each frequency then we can plot a graph with the y-axis as 1/2mv^(max) and x-axis and the threshold frequency and the gradient = plank constant and the y-intercept is the work function
at the stopping voltage, the kinetic energy would be at
a maximum
what is the formula to find the ax Kinetic energy using stopping voltage
1/2mv^2 = e x Vs
compare y= mx + c to the photoelectric effect equation
y(1/2mv^2(max) = m(h) x(f) - work function
