photons and electrons Flashcards
threshold /cut off frequency
minimum frequency of incident radiation at which electrons will be emitted from a particular metal
work function
the minimum amount of energy needed to emit an electron from the surface of a metal
is material specific
photo electric effect
process that occurs when
light shines on a metal and electrons are ejected
establishes the
quantum theory and it illustrates the particle nature of light
wavelength
distance it travels to complete 1 form/cycle
frequency
number of cycles/wave forms per second
infrared + below
on the left
radio,microwave
long wavelength
low frequency therefore low energy
non ionisinh
electromagnetic
ultraviolet + above
right
x-ray, gmaa ray
damaging
short wavelength
high frequency therefore high energy
ionising - radioactivity (“ripping” off electrins)
photon’s liberating electrons
1 photon w/ sufficient energy can liberate 1 electron
if energy of photon less than work function
frequency less than threshold frequency therefore no photoelectric effect
if Eph = Wo
frequency = fo
therefore photo electric effect occurs, e- released
Eph greater than Wo
f greater than fo
photo electric effect occurs , e- released
extra enetgy - Ek (kinetic)
source of atomic emission spectra
Gas discharge tubes energise atoms of an element allowing electrons within each atom to move to higher energy levels. Electrons at high energy levels will fall back down to lower energy levels releasing energy in the form of photons of light. Small atoms with a few electrons and energy levels produce relatively simple emission spectra. Larger atoms with many electrons and energy levels produce very busy emission picture